Abstract:
A compressed gas-powered projectile accelerator is disclosed having an improved means of gas distribution, a valve locking mechanism, an improved combined bumper/seal, and self-contained modular components to improve efficiency, manufacturability, and reduce size and weight.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation of U.S. patent application Ser. No. 10/656,307, filed Sep. 5, 2003, now U.S. Pat. No. 7,237,545, which is a Continuation-in-Part of U.S. patent application Ser. No. 10/090,810, filed Mar. 6, 2002, now U.S. Pat. No. 6,708,685, the contents of which are incorporated fully by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This invention relates, in general, to compressed gas-powered projectile accelerators, generally known as “air-guns”, irrespective of the type of the projectile, gas employed, scale, or purpose of the device. 
     BACKGROUND 
     Compressed gas-powered projectile accelerators have been used extensively to propel a wide variety of projectiles. Typical applications include weaponry, hunting, target shooting, and recreational (non-lethal) combat. In recent years, a large degree of development and invention has centered around recreational combat, where air-guns are employed to launch non-lethal projectiles which simply mark, rather than significantly injure or damage the target. Between launching projectiles such air-guns are generally loaded and reset to fire when the trigger is pulled, generally referred to as “re-cocking” either by an additional manual action by the operator, or pneumatically, as part of each projectile-accelerating event or “cycle”. These devices may be divided into two categories—those that are “non-regulated” or “inertially-regulated”, and those that are “statically-regulated”. 
     Non-regulated or inertially-regulated air-guns direct gas from a single storage reservoir, or set of reservoirs that are continuously connected without provision to maintain a static (zero-gas flow) pressure differential between them, to accelerate a projectile through and out of a tube or “barrel”. The projectile velocity is typically controlled by mechanically or pneumatically controlling the open time of a valve isolating the source gas, which is determined by the inertia and typically spring force exerted on moving parts. Examples of manually re-cocked non-regulated or inertially-regulated projectile accelerators are the inventions of Perrone, U.S. Pat. No. 5,078,118; and Tippmann, U.S. Pat. No. 5,383,442. Examples of pneumatically recocked non-regulated or inertially-regulated projectile accelerators (this type of projectile accelerator being the most commonly used in recreational combat) are the inventions of Tippmann, U.S. Pat. No. 4,819,609; Sullivan, U.S. Pat. No. 5,257,614; Perrone, U.S. Pat. Nos. 5,349,939 and 5,634,456; and Dobbins et al., U.S. Pat. No. 5,497,758. 
     Statically-regulated air-guns transfer gas from a storage reservoir to an intermediate reservoir, through a valve which regulates pressure within the intermediate reservoir to a controlled design level, or “set pressure”, providing sufficient gas remains within the storage reservoir with pressure in excess of the intermediate reservoir set pressure. This type of air-gun directs the controlled quantity of gas within said intermediate reservoir in such a way as to accelerate a projectile through and out of a barrel. Thus, for purposes of discussion, the operating sequence or “projectile accelerating cycle” or “cycle” can be divided into a first step where said intermediate reservoir automatically fills to the set pressure, and a second step, initiated by the operator, where the gas from said intermediate reservoir is directed to accelerate a projectile. The projectile velocity is typically controlled by controlling the intermediate reservoir set pressure. Examples of statically regulated projectile accelerators are the inventions of Milliman, U.S. Pat. No. 4,616,622; 
     More recently, electronics have been employed in both non-regulated and statically-regulated air-guns to control actuation, timing and projectile velocity. Examples of electronic projectile accelerators are the inventions of Rice et al., U.S. Pat. No. 6,003,504; and Lotuaco, III, U.S. Pat. No. 6,065,460. 
     Problems with compressed gas powered guns known to be in the art, relating to maintenance, complexity, and reliability, are illustrated by the following partial list: 
     Sensitivity to liquid CO 2 —The most common gas employed by air-guns is CO 2 , which is typically stored in a mixed gas/liquid state. However, inadvertent feed of liquid CO 2  into the air-gun commonly causes malfunction in both non-regulated or inertially regulated air-guns and, particularly, statically-regulated air-guns, due to adverse effects of liquid CO 2  on valve and regulator seat materials. Cold weather exacerbates this problem, in that the saturated vapor pressure of CO 2  is lower at reduced temperatures, necessitating higher gas volume flows. Additionally, the dependency of the saturated vapor pressure of CO 2  on temperature results in the need for non-regulated or inertially regulated air-guns to be adjusted to compensate for changes in the temperature of the source gas, which would otherwise alter the velocity to which projectiles are accelerated. 
     Difficulty of disassembly—In many air-guns known to be in the art, interaction of the bolt with other mechanical components of the device complicates removal of the bolt, which is commonly required as part of cleaning and routine maintenance. 
     Double feeding—air-guns known to be in the art typically hold a projectile at the rear of the barrel between projectile accelerating cycles. In cases where the projectile is round, a special provision is required to prevent the projectile from prematurely rolling down the barrel. Typically, a lightly spring biased retention device is situated so as to obstruct passage of the projectile unless the projectile is thrust with enough force to overcome the spring bias and push the retention device out of the path of the projectile for sufficient duration for the projectile to pass. Alternatively, in some cases close tolerance fits between the projectile caliber and barrel bore are employed to frictionally prevent premature forward motion of the projectile. However, rapid acceleration of the air-gun associated with movement of the operator is often of sufficient force to overcome the spring bias of retention device, allowing the projectile to move forward, in turn allowing a second projectile to enter the barrel. When the air-gun is subsequently operated, either both projectiles are accelerated, but to lower velocity than would be for a single projectile, or, for fragile projectiles, one or both of the projectiles will fracture within the barrel. 
     Bleed up of pressure—Statically-regulated air-guns require a regulated seal between the source reservoir and intermediate reservoir which closes communication of gas between said reservoirs when the set pressure is reached. Because this typically leads to small closing force margins on the sealing surface, said seal commonly slowly leaks, causing the pressure within the intermediate reservoir to slowly increase or “bleed up” beyond the intended set pressure. When the air-gun is actuated, this causes the projectile to be accelerated to higher than the intended speed, which, with respect to recreational combat, endangers players. 
     Not practical for fully-automatic operation—Air-guns which have an automatic re-cock mechanism can potentially be designed so as accelerate a single projectile per actuation of the trigger, known as “semi-automatic” operation, or so that multiple projectiles are fired in succession when the trigger is actuated, known as “fully-automatic” operation. (Typically air-guns that are designed for fully-automatic operation are designed such that semi-automatic operation is also possible.) Most air-guns known to be in the art are conceptually unsuitable for fully-automatic operation in that there is no automated provision for the timing between cycles required for the feed of a new projectile into the barrel, this function being dependent upon the inability of the operator to actuate the trigger in excess of the rate at which new projectiles enter the barrel when operated semi-automatically. Air-guns known to be in the art which are capable of fully-automatic operation typically accommodate this timing either by inertial means, using the mass-induced resistance to motion of moving components, or by electronic means, where timing is accomplished by electric actuators operated by a control circuit, both methods adding considerable complexity. 
     Difficult manufacturability—Many air-guns known to be in the art, particularly those designed for fully automatic operation, are complex, requiring a large number of parts and typically the addition of electronic components. 
     Stiff or operator sensitive trigger pull—The trigger action of many non-electronic air-guns known to be in the art initiates the projectile accelerating cycle by releasing a latch obstructing the motion of a spring biased component. In many cases, since the spring bias must be quite strong to properly govern the projectile acceleration, the friction associated with the release of this latch results in an undesirably stiff trigger action. Additionally, this high friction contact results in wear of rubbing surfaces. Alternatively, in some cases, to reduce mechanical complexity and circumvent this problem, the trigger is designed such that its correct function is dependent upon the technique applied by the operator, resulting in malfunction if the operator only partially pulls the trigger through a minimum stroke. 
     High wear on striking parts—In many air-guns known to be in the art, particularly those designed for semi-automatic or fully-automatic operation, the travel of some of the moving parts is limited by relatively hard impact with a bumper. Additionally, in many cases, a valve is actuated by relatively hard impact from a slider. The components into which the impact energy is dissipated exhibit increased rates of wear. Further, wear of high impact surfaces in the conceptual design of many air-guns known to be in the art make them particularly un-adaptable to fully-automatic operation. 
     Contamination—Many of the air-guns known to be in the art require a perforation in the housing to accommodate the attachment of a lever or knob to allow the operator to perform a necessary manipulation of the internal components into a ready-to-fire configuration, generally known as “cocking”. This perforation represents an entry point for dust, debris, and other contamination, which may interfere with operation. 
     In another aspect of the present invention, in lieu of direct connection of the valve passage and the chamber, the valve and chamber can be connected indirectly by being both connected to a distribution bus, or gas distribution passage, parallel to the bolt bore and valve passage, which simultaneous allows much greater flexibility of the overall configuration while providing a simple means of distributing gas to other functions such as allowing a simple interface with a passage directing gas to a jet that assists in the introduction of projectiles into the barrel. Additionally, this gas distribution passage provides a simple means of controlling flow to the jet by facilitating the incorporation of a throttling screw at the intersection with the passage communicating gas to the jet. 
     In another embodiment of the present invention, a valve locking feature is provided, whereby force is applied to hold the valve open during the filling of the intermediate reservoir, and then releases the valve body thereafter, reducing the amount of gas pressure required to hold the valve closed during completion of the projectile acceleration cycle. Additionally, because the valve opening force is supplemented by the locking force, the valve spring can be of light design, resulting in an ultra-light trigger pull. In addition, the valve slider diameter can be increased without increasing the spring force acting on the valve slider (with which, through friction, the trigger force scales), thereby allowing the use of larger, more robust seals. Both pneumatic and mechanical techniques to accomplish valve locking are herein described, which can be implemented individually or in combination. 
     It is desirable in many applications to minimize the length of projectile accelerator barrels. In another embodiment of the present invention, the bolt and breech are designed to allow the replacement a bumper with a stationary (not moving with the bolt) combined bumper and seal, thereby eliminating the need for the front bolt seal and allowing the shortening of the bolt and passage in which it slides, and thereby the overall device, by the length along which the seal slides. When not in operation, with no pressure applied within the chamber formed ahead of the step in the bolt diameter and corresponding step in the breech bore, the pressure of the bolt resting against the combined seal and bumper under the force of the bolt spring will maintain a ready seal between the bolt and breech, which will be sustained during operation as the pressure applied by the bolt is replaced by gas pressure, as the bolt moves rearward, sliding within the combined bumper and seal. 
     In many applications it is desirable for the first projectile to be fired as quickly as possible following a pull of the trigger, to minimize time for accidental perturbation of aiming and movement of the target during the time for the compressed gas-powered projectile accelerator action to be complete. Thus, it will be advantageous to have the capability to adjust the first cycle to be faster than subsequent cycles. A method to accomplish these is herein detailed, where a second throttling point at the upstream end of a chamber, in turn upstream of the flow control throttling screw, can be used to allow gas accumulated between cycles within the chamber to fill the intermediate chamber faster on the first cycle than subsequent cycles. 
     The present application provides several methods for the incorporation of a cocking mechanism into the compressed gas-powered projectile accelerator described therein. A novel approach, described herein, embodies a complete cocking system within a plug closing the rear of the valve bore, thereby allowing the cocking capability to contained as a discreet, self-contained module. Further, one embodiment disclosed herein comprises a single piece valve slider comprising of a rear section incorporating the gas seals of the valve and a front portion providing an open cavity partially containing the valve spring and a step by which the sear can latch the valve slider in a non-operating position between cycle. A modification to the valve to include a counter spring can, however, allow the valve slider to be divided into two separate pieces, one acting solely as a valve, and the other containing the velocity control spring and interacting with the sear. So doing simplifies manufacture, and allows the valve to be constructed as a separate module from the remainder of the housing, which is advantageous in allowing a wider range of materials (some of which being unsuitable for use on a larger section of the housing due to weight, but having desirable qualities for use on the valve housing). 
     One embodiment disclosed herein describes a “dynamically-regulated” compressed gas-powered projectile accelerator which fills an intermediate reservoir as an integral part of, and at the beginning of, each projectile accelerating cycle. The cycle is initiated by the operator, preferably by the action of a trigger, which causes the filling of the intermediate reservoir by compressed gas. The second step of the cycle where the projectile is accelerated is then automatically activated when the pressure reaches a design threshold. In so doing, the filling of the intermediate reservoir may be used not only to regulate the projectile velocity, but the time of each cycle, providing numerous advantages. 
     In one embodiment, a gas communicated into a chamber that applies pressure to the valve body (therein denoted the “valve slider”) closes the valve when a design pressure reaches a sufficient level to overcome a spring biasing the valve to open. During venting of the gas into the barrel to accelerate the projectile, however, the device relies partially on the bolt inertia and pressure drop through the gas flow path into the barrel (through a hole or slot connecting to the breech and through the hollow bolt) to hold the valve closed until the firing cycle is complete, and an optional throttling screw is described to enable tuning of a flow restriction governing this pressure drop. This causes some loss of efficiency, in preventing full use of the gas to accelerate the projectile. While use of a stiff bolt spring can minimize the dependence upon the bolt inertia and flow frictional losses to hold the valve closed during venting, the added loading subjects adjoining components to additional wear. 
     Alternatively, dependence upon the bolt inertia and flow losses to hold the valve closed during venting can be avoided by the addition of a valve locking feature, which first applies force to hold the valve open during the filling of the intermediate reservoir, and then releases the valve body thereafter, reducing the amount of gas pressure required to hold the valve closed during completion of the projectile acceleration cycle. Additionally, because the valve opening force is now supplemented by the locking force, the valve spring can be of arbitrarily low stiffness, resulting in an ultra-light trigger pull. Further, the valve slider diameter can be increased without increasing the spring force acting on the valve slider (with which, through friction, the trigger force scales), thereby allowing the use of larger, more robust seals. Both pneumatic and mechanical techniques to accomplish valve locking are herein described, implementable individually or in combination. 
     In many applications it is desirable for the first projectile to be fired as quickly as possible following a pull of the trigger, to minimize time for accidental perturbation of aiming and movement of the target during the time for the compressed gas-powered projectile accelerator action to complete. A means for adjusting the cycle to a relatively slow rate, and, for adjusting the first cycle to be faster than subsequent cycles is herein detailed, where a second throttling point at the upstream end of a chamber, in turn upstream of the flow control throttling screw of the compressed gas-powered projectile accelerator, can be used to allow gas accumulated between cycles within the chamber to fill the intermediate chamber faster on the first cycle than subsequent cycles. 
     A unique cocking means is disclosed herein, embodying a complete cocking system within a plug closing the rear of the valve bore, thereby allowing the cocking capability to be added or removed as a discreet, self contained module. 
     SUMMARY 
     While some compressed gas-powered projectile accelerators known in the art circumvent some of the above listed problems, all of these and other problems are mitigated or eliminated by the compressed gas-powered projectile accelerator of the present invention. The compressed gas-powered projectile accelerator of the present invention employs a “dynamically-regulated” cycle to avoid the problems associated with both non-regulated or inertially regulated air-guns and statically-regulated air-guns. 
     The term “dynamically regulated” refers to the fact that the compressed gas-powered projectile accelerator of the present invention, in contrast to air-guns known to be in the art, fills an intermediate reservoir as an integral part of, and at the beginning of, each projectile accelerating cycle. The cycle is initiated by the operator, preferably by the action of a trigger, which causes the filling of the intermediate reservoir by compressed gas. The second step of the cycle where the projectile is accelerated is then automatically activated when the pressure reaches a set pressure threshold. In so doing, the filling of the intermediate reservoir may be used not only to regulate the projectile velocity, but the time of each cycle, making fully automatic operation possible without necessity for inertial or electronic timing. Additionally, since the gas in the intermediate reservoir is used as soon as the pressure reaches the set pressure, the problem of potential bleed-up of the pressure in the intermediate reservoir is eliminated. For further illustration, the type of regulation employed by the compressed gas-powered projectile accelerator of the present invention may be contrasted with that employed by statically-regulated air-guns known to be in the art, where the intermediate reservoir is automatically filled to the set pressure, and the gas stored until the projectile accelerating step of the cycle is triggered by the operator. 
     This unique cycle additionally maximizes reliability and minimizes wear by allowing all sliding components to rotate freely and requiring no hard impact or high pressure sliding contact between components. The simplicity of assembly allows the housing of the compressed gas-powered projectile accelerator of the present invention to be made as a single piece and the few moving parts can be easily removed for inspection and cleaning. 
     In another embodiment of the present invention, an additional “gas distribution shaft” is provided, and a valve passage is connected to the gas distribution shaft instead of directly to the chamber. The gas distribution shaft then conducts gas into a passage leading to a chamber between the receiver and bolt diametrical steps, but also can be used to deliver gas at equal pressure to other locations to power additional functions, and can easily incorporate throttling points at either end to allow adjust these functions where throttling provides a desirable measure of control. Because the gas distribution passage makes gas available at any position along the length of the housing, gas delivery to any position along the housing length can be accomplished with minimal impact to geometry. 
     In another embodiment, gas can be directed to aid in chambering of projectiles by a vertical shaft connecting the gas distribution shaft to a jet in the ball feed assembly, and the geometry of the gas distribution shaft allows a throttling screw to be incorporated at the intersection of the vertical shaft and gas distribution shaft at minimal cost. 
     In another embodiment, gas can be directed into an annular chamber in the valve passage to firstly pneumatically lock the valve into an open position when a projectile acceleration cycle is initiated, and secondly unlock the valve when gas pressure is being released to accelerate the valve, thereby holding the valve open longer and allowing a greater fraction of the gas to be applied to the acceleration of the projectile before the valve reopens, initiating another projectile acceleration cycle. Alternatively, the same affect can be achieved by a mechanical valve locking cam. 
     In another embodiment, the bumper located ahead of the step in the bolt diameter can be designed to form a seal between the bolt and the receiver passage step, preferably being an appropriately sized o-ring, thereby eliminating the need for the front bolt o-ring and allowing the receiver passage to be shortened by the length through which the front bolt o-ring would ordinarily travel. 
     In another embodiment, a second throttling point at the upstream end of the source gas passage can be used to allow gas accumulated between cycles within the source gas passage to cause the chambers ahead of and behind the larger diameter section of the bolt to fill faster on the first cycle that subsequent cycles, thereby allowing the first cycle to be timed differently than subsequent cycles, the first cycle primarily being controlled by the throttling point closest to the valve passage, and subsequent cycles primarily being controlled by the more upstream throttle point. 
     In another embodiment, the ability to cock the compressed gas-powered projectile accelerator can be accomplished by the addition of a discreet cocking assembly, said cocking assembly being a self-contained component which can provide the optional capability to manually cock the unit without a cocking assembly having to be built into the valve or housing. 
     In another embodiment, a discreet valve module has been devised where the slider can be divided into two parts, and the valve made as a separate component from the main housing, facilitating manufacture, interfacing and fabrication of connecting passages, and use of alternate construction materials from the housing. The valve module can also incorporate a cocking feature to make an entirely self contained, sealed valve/cocking assembly. 
     In another embodiment, an additional “gas distribution passage” is employed, and a valve passage connected to said gas distribution shaft rather than directly to said chamber. Said gas distribution passage then conducts gas into a passage leading to said chamber between the breech and bolt diametrical steps, but also can be used to deliver gas at equal pressure to other locations to power additional functions, and can easily incorporate throttling points at either end to allow adjustment of these functions where throttling provides a desirable measure of control. Because the gas distribution passage makes gas available at any position along the length of the housing, gas delivery to any position along the housing length can be accomplished with minimal impact to geometry as a specific example, gas can be directed to aid in chambering of projectiles by a vertical shaft connecting the gas distribution shaft to a jet in the ball feed assembly, and the geometry of the gas distribution shaft facilitates the incorporation of a throttling screw at the intersection of the vertical shaft and gas distribution passage. 
     In another embodiment, gas can be directed into an annular chamber in the valve passage to firstly pneumatically lock the valve into an open position when a projectile acceleration cycle is initiated, and secondly unlock the valve when gas pressure is being released to accelerate a projectile, thereby holding the valve open longer and allowing a greater fraction of the gas to be applied to the acceleration of the projectile before the valve reopens, initiating another projectile acceleration cycle. Alternatively, the same affect can be achieved by a mechanical valve locking cam. 
     In another embodiment, the bumper located ahead of the step in the bolt diameter can be designed to form a seal between the bolt and the breech wall, preferably being an appropriately sized o-ring, thereby eliminating the need for the front bolt seal and allowing the receiver passage to be shortened by the length through which the front bolt seal would ordinarily travel. 
     In another embodiment, a second throttling point at the upstream end of the source gas passage can be used to allow gas accumulated between cycles within the source gas passage to cause the chambers ahead of and behind the larger diameter section of the bolt to fill faster on the first cycle that subsequent cycles, thereby allowing the first cycle to be timed differently than subsequent cycles, the first cycle primarily being controlled by the throttling point closest to the valve passage, and subsequent cycles primarily being controlled by the more upstream throttle point. 
     In another embodiment, the ability to cock the compressed gas-powered projectile accelerator can be accomplished by the addition of a discreet cocking assembly, the cocking assembly being a self-contained component which can provide the optional capability to manually cock the unit without a cocking assembly having to be built into the valve or housing. 
     In another embodiment, a discreet valve module has been devised where the slider can be divided into two parts, and the valve made as a separate component from the main housing, facilitating manufacture, interfacing and fabrication of connecting passages, and use of alternate construction materials from the housing. The valve module can also incorporate a cocking feature to make an entirely self contained, sealed valve/cocking assembly. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view from the side of a compressed gas-powered projectile accelerator made according to the present invention. 
         FIG. 2  is a view from the rear of a compressed gas-powered projectile accelerator made according to the present invention. 
         FIG. 3  is a sectional view from the front of a compressed gas-powered projectile accelerator made according to the present invention, taken along line  3 - 3  of  FIG. 1 . 
         FIG. 4  is a sectional view from the side of a compressed gas-powered projectile accelerator made according to the present invention with internal components removed to show internal cavities and passages, taken along line  4 - 4  of  FIG. 2 . 
         FIG. 5  is a sectional view from the side of upper rear portion of a compressed gas-powered projectile accelerator identified in  FIG. 4  made according to the present invention shown enlarged, with internal components removed to show internal cavities and passages. 
         FIG. 6  is a sectional view from the side of upper rear portion of a compressed gas-powered projectile accelerator made according to the present invention shown enlarged where test/bleed ports have been eliminated by welding and strategic orientation of the rear passage, with internal components removed to show internal cavities and passages. 
         FIG. 7  is a sectional view from the side of upper rear portion of a compressed gas-powered projectile accelerator made according to the present invention shown enlarged where the bolt rest-point passage and rear passage have been replaced by a slot, eliminating corresponding perforations in the upper housing, with internal components removed to show internal cavities and passages. 
         FIG. 8  is a sectional view from the side of a compressed gas-powered projectile accelerator made according to the present invention. 
         FIG. 9  is a sectional view from the side of the upper rear portion of a compressed gas-powered projectile accelerator identified in  FIG. 9  made according to the present invention shown in detail with purge holes in the spring guide. 
         FIG. 9(A)  is a detailed and enlarged view of the compressed gas-powered projectile accelerator shown in  FIG. 9 . 
         FIG. 10  is a sectional view from the side of the upper rear portion of a compressed gas-powered projectile accelerator made according to the present invention shown in detail with a truncated spring guide eliminating need for purge holes. 
         FIG. 11  is a sectional view from the side of the upper rear portion of a compressed gas-powered projectile accelerator made according to the present invention shown in detail with purge holes in the spring guide and an enlarged bolt spring. 
         FIG. 12  is a sectional view from the side of the upper rear portion of a compressed gas-powered projectile accelerator made according to the present invention shown in detail with a truncated spring guide, an enlarged bolt spring, and purge holes in the bolt instead of the spring guide. 
         FIG. 13  is a view from the side of the front portion of a compressed gas-powered projectile accelerator made according to the present invention shown in detail. 
         FIG. 14  is a view from the side of the region identified in  FIG. 13  in the vicinity of the trigger of a compressed gas-powered projectile accelerator made according to the present invention shown in detail. 
         FIGS. 15A and 15B  are sectional views from the rear of the region taken along lines  15 A- 15 A and  15 B- 15 B identified in  FIG. 14  in the vicinity of the trigger of a compressed gas-powered projectile accelerator made according to the present invention showing the mode-selector cam in the semi-automatic and fully-automatic positions, respectively, with ball and spring retention assembly, shown in detail. 
         FIGS. 16A and 16B  are sectional views of the region taken along lines  16 A- 16 A and  16 B- 16 B identified in  FIG. 14  in the vicinity of the trigger of a compressed gas-powered projectile accelerator made according to the present invention, as viewed diagonally from the lower rear, showing the safety cam in the non-firing and firing positions, respectively, with ball and spring retention assembly, shown in detail. 
         FIGS. 17A-I  are sectional views from the side of a compressed gas-powered projectile accelerator made according to the present invention, illustrating semi-automatic operation. 
         FIGS. 18A-H  are sectional views from the side of a compressed gas-powered projectile accelerator made according to the present invention, illustrating fully-automatic operation. 
         FIG. 19  is a view from the side of the front portion of a compressed gas-powered projectile accelerator made according to the present invention with the addition of a cocking knob, shown in detail. 
         FIG. 20  is a sectional view from the top taken along line  20 - 20  of  FIG. 19  of the front portion of a compressed gas-powered projectile accelerator made according to the present invention with the addition of a cocking knob, shown in detail. 
         FIG. 21  is a view from the side of the front portion of a compressed gas-powered projectile accelerator made according to the present invention with the addition of a cocking manifold, slider, and spring assembly, shown in detail. 
         FIG. 22  is a sectional view from the top taken along line  22 - 22  of  FIG. 21  of the front portion of a compressed gas-powered projectile accelerator made according to the present invention with the addition of a cocking manifold, slider, and spring assembly, shown in detail. 
         FIG. 23  is a sectional view from the side of the region identified in  FIG. 8  in the vicinity of the source gas passage of a compressed gas-powered projectile accelerator made according to the present invention, shown in detail. 
         FIG. 24  is a sectional view from the side of the region in the vicinity of the source gas passage of a compressed gas-powered projectile accelerator made according to the present invention with baffle inserts inside the source gas passage, shown in detail. 
         FIG. 25  is a sectional view from the side of the region in the vicinity of the source gas passage of a compressed gas-powered projectile accelerator made according to the present invention with regulator components inserted inside the source gas passage, shown in detail. 
         FIG. 26  is a view from the side of a compressed gas-powered projectile accelerator made according to the present invention with an pneumatically assisted feed system. 
         FIG. 27  is a view from the rear of a compressed gas-powered projectile accelerator made according to the present invention with a pneumatically assisted feed system. 
         FIG. 28  is a sectional view from the front taken along line  28 - 28  of  FIG. 26  of a compressed gas-powered projectile accelerator made according to the present invention with a pneumatically assisted feed system. 
         FIG. 29  is a sectional view from the side taken along line  29 - 29  in  FIG. 27  of a compressed gas-powered projectile accelerator made according to the present invention with a pneumatically assisted feed system. 
         FIG. 30  is a view from the rear of a compressed gas-powered projectile accelerator made according to the present invention with a variable volume chamber connected to the valve passage. 
         FIG. 31  is a sectional view from the top taken along line  31 - 31  of  FIG. 30  of a compressed gas-powered projectile accelerator made according to the present invention with a variable volume chamber connected to the valve passage. 
         FIG. 32  is a sectional view from the top of a compressed gas-powered projectile accelerator made according to the present invention with a variable volume chamber connected to the valve passage and with the valve slider spring replaced by a pneumatic piston. 
         FIG. 33  is a view from the rear of an electronic compressed gas-powered projectile accelerator made according to the present invention. 
         FIG. 34  is a sectional view from the side taken along line  34 - 34  of  FIG. 33  of an electronic compressed gas-powered projectile accelerator made according to the present invention. 
         FIG. 35  is a view from the rear of an electronic compressed gas-powered projectile accelerator made according to the present invention with a pressure transducer connected to the rear of the valve passage. 
         FIG. 36  is a sectional view from the side taken along line  36 - 36  of  FIG. 35  of an electronic compressed gas-powered projectile accelerator made according to the present invention with a pressure transducer connected to the rear of the valve passage. 
         FIG. 37  is a view from the side of an additional embodiment of the compressed gas-powered projectile accelerator of the present invention. 
         FIG. 38  is a view from the rear of the compressed gas-powered projectile accelerator of the present invention shown in  FIG. 37 . 
         FIG. 39  is a sectional view from the side taken along line  3 - 3  of  FIG. 38  of a compressed gas-powered projectile accelerator made with improvements of the present invention. 
         FIG. 40  is a sectional view from the front taken along line  40  of  FIG. 37  of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the intersection of the feed-assist shaft and gas distribution shaft, shown to advantage. 
         FIG. 41  is a sectional view from the rear taken along line  41  of  FIG. 37  of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the valve locking shaft, shown to advantage. 
         FIG. 42  is a sectional view from the rear taken along line  42  of  FIG. 37  of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the upper gas feed passage, shown to advantage. 
         FIG. 43  is a sectional view from the rear taken along line  43  of  FIG. 37  of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the lower gas feed passage, shown to advantage. 
         FIG. 44  is a sectional view from the front of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the intersection of the feed-assist shaft and gas distribution shaft showing an optional feed gas vent on one side of the barrel, shown to advantage. 
         FIG. 45  is a sectional view from the side of the rear portion of the valve passage of a compressed gas-powered projectile accelerator identified in  FIG. 39  made with improvements of the present invention, shown to advantage. 
         FIG. 46  is a sectional view from the side of the rear portion of the valve passage of a compressed gas-powered projectile accelerator made with improvements of the present invention, showing an annular enlargement of the valve passage at the lower feed passage intersection to advantage. 
         FIG. 47  is a sectional view from the side of the rear portion of the valve passage of a compressed gas-powered projectile accelerator made with improvements of the present invention, showing an annular enlargement of the valve passage at the lower feed passage intersection and dual o-ring seal to advantage. 
         FIG. 48  is a sectional view from the side of a compressed gas-powered projectile accelerator made with improvements of the present invention with the addition of a second throttling screw in the source gas passage. 
         FIG. 49  is a sectional view from the side of a compressed gas-powered projectile accelerator made with improvements of the present invention, prior to operation, showing a valve locking cam in the non-locking position. 
         FIG. 50  is a sectional view from the side of the front portion of a compressed gas-powered projectile accelerator identified in  FIG. 49  made with improvements of the present invention, prior to operation, showing a valve locking cam in the non-locking position, shown to advantage. 
         FIG. 51  is a sectional view from the side of the front portion of a compressed gas-powered projectile accelerator made with improvements of the present invention, during operation, showing a valve locking cam in a locking position, shown to advantage. 
         FIG. 52  is a view from the side of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention. 
         FIG. 53  is a view from the rear of an alternate embodiment of a compressed gas-powered projectile accelerator identified in  FIG. 52  made with improvements of the present invention. 
         FIG. 54  is a sectional view from the side taken along line  54  of  FIG. 53  of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention. 
         FIG. 55  is a sectional view from the front taken along line  55  of  FIG. 52  of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the intersection of the vertical source gas shaft, shown to advantage. 
         FIG. 56  is a sectional view from the front taken along line  56  of  FIG. 52  of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the intersection of the feed-assist shaft and gas distribution passage, shown to advantage. 
         FIG. 57  is a sectional view from the rear taken along line  57  of  FIG. 52  of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the vertical shaft connecting the valve module slot and gas distribution passage, shown to advantage. 
         FIG. 58  is a sectional view from the rear taken along line  58  of  FIG. 52  of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of the rear source gas shaft, shown to advantage. 
         FIG. 59  is a sectional view from the top of an alternate embodiment of a compressed gas-powered projectile accelerator made with improvements of the present invention in the vicinity of a source gas passage incorporated into the upper housing. 
         FIG. 60  is a view from the side of a valve module made according to the present invention, shown to advantage. 
         FIG. 61  is a view from the top of a valve module made according to the present invention, shown to advantage. 
         FIG. 62  is a sectional view from the side taken along line  62  of  FIG. 61  of a valve module made according to the present invention shown to advantage. 
         FIG. 63  is a sectional view from the top taken along line  63  of  FIG. 60  of a valve module made according to the present invention, shown to advantage. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A preferred embodiment of a compressed gas-powered projectile accelerator of the present invention is here and in Figures disclosed. For clarity, within this document all reference to the top and bottom of the compressed gas-powered projectile accelerator will correspond to the accelerator as oriented in  FIG. 1 . Likewise, all reference to the front of said accelerator will correspond to the leftmost part of said accelerator as viewed in  FIG. 1 , and all reference to the rear of said accelerator will correspond to the rightmost part of said accelerator as viewed in  FIG. 1 . Referring to the Figures, the gas-powered accelerator of the present invention includes, generally: 
     A housing  1 , preferably made of a single piece, shown in the Figures in the preferred shape of a pistol which is penetrated by hollow passages which contain the internal components. 
     A preferably cylindrical receiver passage  2  forms a breech  3  and barrel  4 , the latter being preferably extended by the addition of a tubular member, hereafter denoted the “barrel extension”  5 , which is preferably screwed into the housing  1  or otherwise removably attached. The barrel  4  is intersected by a projectile feed passage  6  into which projectiles are introduced from outside the housing  1 . The projectile feed passage  6  may meet the barrel  4  at an angle but preferably may be at least partially vertically inclined to take advantage of gravity to bias projectiles to move into the barrel  4 ; conversely an alternate bias, such as a spring mechanism may be employed. The projectile feed passage  6  may connect such that its center axis intersects the center axis of the barrel  4 , or, as shown in the examples in the Figures, the projectile feed passage  6  center axis can be offset from the center axis of the barrel  4 , as long as the intersection forms a hole sufficiently sized for the passage of projectiles from the projectile feed passage  6  into the barrel  4 . Also, the breech  3  diameter may optionally be slightly less than that of the barrel  4  immediately rearward of where the projectile feed passage  6  intersects the barrel  4  to help prevent projectiles from sliding or rolling rearward, as shown in  FIG. 4 . The examples shown in the Figures are designed to introduce spherical projectiles under the action of both gravity and suction, and includes a cap  7  at the end of the projectile feed passage  6  to prevent movement of projectiles beyond the entry point into the barrel  4 . This “projectile feed passage cap”  7  can be designed to be rotatable, with a beveled surface at the point of contact with projectiles, such that in one orientation said projectile feed passage cap  7  will facilitate movement of projectiles into the barrel  4 , but, when rotated 174.degree. will prevent movement of projectiles into the barrel  4 . 
     Preferably parallel to the receiver passage  2  is a preferably cylindrical valve passage  8  of varying cross section which is connected to the breech  3  by a gas feed passage  9 , a bolt rest-point passage  10 , and a rear passage  11 . The valve passage  8  is intersected by a source gas passage  12  and a trigger cavity  13 , which is perforated in several places to allow extension of control components to the exterior of the housing  1 . The source gas passage  12  is preferably valved, preferably by the use of a screw  14 , the degree to which partially or completely blocks the source gas passage  12  depending on the depth to which the screw  14  has been adjusted into a partially threaded hole in the housing  1 , intersecting the source gas passage  12 . Alternatively, the gas feed passage  9  may be similarly valved instead of, or in addition to, the source gas passage  12  to control flow both between the source gas passage  12  and breech  3 , and between the source gas passage  12  and valve passage  8 . The screw  14  must form a seal with the hole in which it sits, preferably by the use of one or more o-rings in grooves  15 . The source gas passage  12  will preferably include an expanded section  16  to minimize liquid entry and maximize consistency of entering gas by acting as a plenum. Gas is introduced through the source gas passage inlet  17  at the base of the housing  1 , which may be designed to accept any high pressure fitting. A gas cylinder, which may be mounted to the housing  1 , preferably to the base of the housing  1  in front of the optional trigger guard  18  illustrated in  FIG. 1  or immediately to the rear of the source gas passage inlet  17 , may be connected to said fitting, preferably by a flexible high pressure hose. The source gas passage  12  is depicted preferably integrated into the lower rear part of the housing  1  to facilitate manufacture of the housing  1  from a single piece of material, but it is to be appreciated that any orientation of the source gas passage  12 , either within the housing  1  or an attachment made to the housing  1  of the compressed gas-powered projectile accelerator of the present invention, will not alter the inventive concepts and principles embodied therein. 
     A sectional view from the side of the housing with most internal components removed is shown in  FIG. 4  for clarity. Optional test/bleed ports  19 ,  20 ,  21  are shown connecting the breech  3  to the outside of the housing  1 , blocked by removable plugs  22 ,  23 ,  24  because they are formed as part of manufacture of the gas feed passage  9 , bolt rest-point passage  10 , and rear passage  11  of this preferred embodiment. Said ports  19 ,  20 ,  21  and plugs  22 ,  23 ,  24  are optional because they are not required for correct function of the projectile accelerator of the present invention. Said ports  19 ,  20 ,  21  may be eliminated from the design by a variety of means, such as the welding shut of said ports  19 ,  20 ,  21 , use of special tooling, or by strategic routing of the gas feed passage  9 , the bolt rest-point passage  10 , and/or, in particular, the rear passage  11  which may be oriented such that it may be drilled either from the rear of the breech  3  or from the bottom. The breech  3  is shown enlarged in  FIG. 5 . In  FIG. 6  the breech  3  is shown in detail with the front test/bleed port  19  and middle test/bleed port  20  eliminated by welding and rear passage  11  oriented such that it may be manufactured without additional perforation of the breech  3  or need of special tooling such as a small right-angle drill. A third option is shown in  FIG. 7  where the bolt rest-point passage  10 , and rear passage  11  are replaced by a single slot  25 , eliminating the corresponding perforations at the top of the breech  3 . 
     Passages  9 ,  10 ,  11  and/or bleed/test ports  19 ,  20 ,  21  may be individually optionally valved to control gas flow, preferably by the use of screws, the degree to which partially or completely block the passage or passages  9 ,  10 , and/or  11 , and/or bleed/test ports  19 ,  20 , and/or  21 , depending on the depth to which the screws have been adjusted into threaded holes appropriately made in the housing  1 , intersecting the passage or passages  9 ,  10 , and/or  11  and/or ports  19 ,  20 , and/or  21 . The preferred embodiment depicted in the Figures herein includes an exemplary valve screw  26  at the junction between the rear passage  11  and valve passage  8 . 
     Referring now to  FIG. 8 , a hollow slider, having one or, as shown in  FIG. 8 , a plurality of holes  27  on the front surface, matching the shape of the barrel  4  and breech  3 , preferably free to rotate about a central axis parallel to the receiver passage  2  to minimize wear, and preferably made of a single piece, generally referred to as a bolt  28 , can slide within the receiver passage  2  and around a preferably cylindrical spring-guide  29 , which has a hollow space at the forward end which communicates with said forward end a plurality of holes about its circumference which allow compressed gas to pass through the bolt  28  and will hence be denoted “purge holes”  30 . A preferably elastic bumper or “bolt bumper”  31  is attached to the bolt  28  at a point where the bolt  28  changes diameter, limiting its forward travel and easing shock in the event of malfunction. (The projectile accelerator of the present invention can be designed such that the bolt  28  does not experience high impact against the housing  1 .) A spring or “bolt spring”  32  surrounds the spring-guide  29 , which is attached, preferably by a screw  33  to a removable breech cap  34 , which closes the rear of the breech  3 , preferably by being screwed into the housing  1 . The bolt  28  and spring guide  29  are shown with preferable o-ring/groove type gas seals  35 ,  36 ,  37 , although the type of sealing required at these locations is arbitrary. A preferably cylindrical elastic bumper  38  which protects the bolt  28  and breech cap  34  in the event of malfunction is held in place between the spring guide  29  and breech cap  34 , partially surrounding the bolt spring  32  and spring guide  29 . The breech cap  34 , bumper  38 , spring guide  29 , bolt spring  32 , and rear part of the bolt  28  and housing  1  are shown in detail in  FIG. 9 .  FIG. 9(A)  is an enlarged and detailed view of the bolt  28 , bumper  38 , bolt sprint  32 , bolt rear seal  36 , gas feed passage  9 , and valve slider  39 , of the present invention. 
     Alternate configurations of these components are shown in detail in  FIG. 10 , where instead of having a hollow space at the forward end and purge holes  30 , the spring guide  29  is truncated to allow the passage of gas through the bolt  28 ;  FIG. 11 , where the bolt spring  32  diameter is in detail to reduce wear on the spring guide o-ring  37  (or other seal type) and the bumper  38  resides partly inside the bolt spring  32 ; and  FIG. 12 , where the spring guide  29  is again truncated and the purge holes  30  are incorporated into the rear part of the bolt  28 . 
     A partially hollow slider or “valve slider”  39  matching the shape of the valve passage  8  as shown in  FIG. 8 , preferably free to rotate about its axis parallel to the receiver passage  2  to minimize wear, particularly from contact with the sear  40  described below, can slide within the valve passage  8 . The valve slider  39  forms seals with the valve passage  8  at two points—where single o-ring/groove type seals  41 ,  42  are shown for illustration, but multiple o-rings or any other appropriate type of seal may be used; e.g. use of a flexible material such as polytetrafluoroethylene at these points to form surface-to-surface seals in lieu of o-rings can potentially reduce wear on these seals  41 ,  42 . 
     A preferably removable hollow valve passage cap  43 , preferably screwed into the housing  1 , traps an optional bumper or “valve bumper”  44  which protects the valve passage cap  43  from wear by contact with the valve slider  39  and vice-versa. A spring or “valve spring”  45  within the valve passage  8 , which may be accepted partially within the valve slider  39 , and valve passage cap  43 , pushes against the valve slider  39  and against a screw  46  preferably threaded inside of the valve passage cap  43 , the position of which may be adjusted to increase or decrease tension in the spring  45 , thereby adjusting the operating pressure of the cycle and magnitude of projectile acceleration. An optional internal guide  47  for the valve spring can be added. The valve slider  39  can be held in a forward “cocked” position by a sear  40 , which can rotate about and slide on a pivot  48 . A spring  49  maintains a bias for the sear  40  to slide forward and rotate toward the valve slider  39 . Sliding travel of the sear  40  can be limited by means of a preferably cylindrical sliding cam or “mode selector cam”  50  of varying diameter shown in detail in  FIGS. 14 ,  15 A, and  15 B, the positions corresponding to semi-automatic and fully-automatic being shown in  FIGS. 15A and 15B , respectively. Position of the mode selector cam  50  is maintained and its travel limited by the ball  51  and spring  52  arrangement shown, which are retained within the housing  1  by the screw  53  shown. 
     A lever or “trigger”  54  which rotates on a pivot  55  can press upon the sear  40 , inducing rotation of the sear  40 . A bias of the trigger  54  to rotate toward the sear  40  (clockwise in  FIG. 8 ) is maintained by spring  56 . Rotation of the trigger  54  can be limited by means of a preferably cylindrical sliding cam or “safety cam”  57  of varying diameter shown in detail in  FIGS. 14 ,  16 A, and  16 B, the firing and non-firing positions being shown in  FIGS. 16A and 16B , respectively. Position of the safety cam  57  is maintained and its travel limited by the ball  58  and spring  59  arrangement shown, which are preferably retained within the housing  1  by the screw  60  shown. 
     Semi-automatic operation of the compressed gas-powered projectile accelerator of the present invention is here described: 
     The preferred ready-to-operate configuration for semi-automatic operation is shown in  FIG. 17A , with the valve slider  39  in its cocked position, resting against the sear  40 , which, under the pressure of the valve spring  45  translated through the valve slider  39 , rests in its rearmost position. The safety cam  57  is positioned to allow the trigger  54  to rotate freely. The mode selector cam  50  is positioned so as to not restrict the forward travel of the sear  40 . The smaller diameters of the safety cam  57  and mode selector cam  50  are shown in this cross section, as said smaller diameters represent the portions of these components interacting with the trigger  54  and sear  40 , respectively. A projectile  61  is positioned to enter the barrel  4 . The illustrated projectile is a spherical projectile  61  as an example. The projectile  61  is prevented from entering the barrel  4  by interference with the bolt  28 . 
     The trigger  54  is then pulled rearward, pulling the sear  40  downward, disengaging it from the valve slider  39 , as shown in  FIG. 17B . 
     Shown in  FIG. 17C , under the force applied by the valve spring  45 , the valve slider  39  then slides rearward, until it is stopped preferably by mechanical interference with the changing diameter of the valve passage  8 , allowing gas to flow through the gas feed passage  9  into the region of the breech  3  ahead of the bolt rear seal  36 . Simultaneously, the sear  40  is caused to slide forward and rotate (clockwise in the drawing) by the sear spring  49 , coming to rest against the valve slider  39 , being now disengaged from the trigger  54 . 
     Shown in  FIG. 17D , the pressure of the gas causes the bolt  28  to slide rearward, until the bolt rear seal  36  passes the front edge of bolt rest-point passage  10 , opening a flow path, and allowing gas into the bolt rest-point passage  10 , valve passage  8  rearward of the valve slider  39 , rear passage  11 , and region of the breech  3  to the rear of the bolt  28 . The externally applied bias of the projectile  61  to enter the barrel  4 , here assumed to be gravity as an example, acts to push a projectile  61  into the barrel  4 , aided by the suction induced by the motion of the bolt  28 . Additional projectiles in the projectile feed passage  6  are blocked from entering the barrel  4  by the projectile  61  already in the barrel  4 . The combined force of the bolt spring  32  and the pressure behind the bolt  28  bring the bolt  28  to rest, preferably without contacting the breech cap bumper  38  at the rear of the breech  3 . The breech  3 , valve passage  8  rearward of the valve slider  39 , and all contiguous cavities not isolated by seals within the housing  1  may here be recognized as the intermediate reservoir discussed in the background of the invention. The bolt  28  will remain approximately at rest, where its position will only adjust slightly to allow more or less gas through the bolt rest-point passage  10  as required to maintain a balance of pressure and spring forces on it while the pressure continues to increase. 
     Shown in  FIG. 17E , once the pressure in the valve passage  8  rearward of the valve slider  39  has increased sufficiently to overcome the force of the valve spring  45  on the valve slider  39 , the valve slider  39  will be pushed forward until it contacts the valve bumper  44  if present, or valve passage cap  43  if no valve bumper  44  is present, thereby simultaneously stopping the flow of compressed gas from the source gas passage  12 , and allowing the flow of gas from the region of the breech  3  ahead of the bolt rear seal  36  through the feed passage, into the valve passage  8  rearward of the valve slider  39 , which is in communication with the region of the breech  3  behind the bolt  28 . The sear  40 , under the action of the sear spring  49 , will rotate further (clockwise in the drawing) once the largest diameter section of the valve slider  39  has traveled sufficiently far forward to allow this, coming to rest against the portion of the valve slider  39  rearward of its said largest diameter section. 
     The bolt  28  is then driven forward by now unbalanced pressure and spring forces on its surface, pushing the projectile  61  forward in the barrel  4  and blocking the projectile feed passage  6 , preventing the entry of additional projectiles. When the bolt  28  reaches the position shown in  FIG. 17F , gas flows through the purge holes  30  in the spring guide  29 , through the center of the bolt  28 , and through the plurality of holes  27  on the front surface of the bolt  28 , which distribute the force of the flowing gas into uniform communication with the rear surface of the projectile  61 . 
     Shown in  FIG. 17G  and further in  FIG. 17H , the action of the gas pressure on the projectile  61  will cause it to accelerate through and out of the barrel  4  and barrel extension  5 , at which time the barrel, barrel extension  5 , breech  3 , valve passage  8  rearward of the valve slider  39 , and all communicating passages which are not sealed will vent to atmosphere. 
     Shown in  FIG. 17H , when the pressure within the valve passage  8  rearward of the valve slider  39  has been reduced to sufficiently low pressure such that the force induced on the valve slider  39  no longer exceeds that of the valve spring  45 , the valve slider  39  will slide rearward until its motion is restricted by the sear  40 . The sear  40  will rest against the front of the trigger  54 , and may exert a (clockwise in drawing) torque helping to restore the trigger  54  to its resting position, depending on the design of the position of the trigger pivot  55  relative to the point of contact with the valve slider  39 . 
     Under the action of the bolt spring  32 , the bolt  28  will continue to move forward, compressing gas within the space ahead of the bolt rear seal  36  in so doing, and, allowing only a small gap by which the gas may escape into the valve passage  8 , the bolt  28  will be decelerated, minimizing wear on the bolt bumper  31  and stopping in its preferred resting position, as shown in  FIG. 17I . 
     When the trigger  54  is released, the action of the trigger spring  56 , sear spring  49 , and valve spring  45  will return the components to the preferred ready-to-fire configuration, shown in  FIG. 17A . 
     Fully-automatic operation of the compressed gas-powered projectile accelerator of the present invention is here described: 
     The preferred ready-to-operate configuration for fully-automatic operation is shown in  FIG. 18A , with the valve slider  39  in its cocked position, resting against the sear  40 , which, under the pressure of the valve spring  45  translated through the valve slider  39 , rests in its rearmost position. The safety cam  57  is positioned to allow the trigger  54  to rotate freely. The mode selector cam  50  is positioned so as to restrict the forward travel of the sear  40 . The smaller diameter of the safety cam  57  and larger diameter of the mode selector cam  50  are shown in this cross section, as said diameters represent the portions of these components interacting with the trigger  54  and sear  40 , respectively. A projectile  61  with an arbitrary externally applied bias to enter the barrel  4 , here a spherical projectile being used as an example, is prevented from entering the barrel  4  by interference with the bolt  28 . 
     The trigger  54  is then pulled rearward, pulling the sear  40  downward, disengaging it from the valve slider  39 , as shown in  FIG. 18B . 
     Shown in  FIG. 18C , under the force applied by the valve spring  45 , the valve slider  39  then slides rearward, until it is stopped preferably by mechanical interference with the changing diameter of the valve passage  8 , allowing gas to flow through the gas feed passage  9  into the region of the breech  3  ahead of the bolt rear seal  36 . The mode selector cam  50  prevents the sear  40  from sliding forward sufficiently far to disengage from the trigger  54 . 
     Shown in  FIG. 18D , the pressure of the gas causes the bolt  28  to slide rearward, until the bolt rear seal  36  passes the front edge of the bolt rest-point passage  10 , allowing gas into the bolt rest-point passage  10 , valve passage  8  rearward of the valve slider  39 , rear passage  11 , and region of the breech  3  behind the bolt  28 . The externally applied bias of the projectile  61  to enter the barrel  4 , here assumed to be gravity as an example, acts to push a projectile  61  into the barrel  4 , aided by the suction induced by the motion of the bolt  28 . Additional projectiles in the projectile feed passage  6  are blocked from entering the barrel  4  by the projectile  61  already in the barrel  4 . The combined force of the bolt spring  32  and the pressure behind the bolt  28  bring the bolt  28  to rest, preferably without contacting the breech cap bumper  38  at the rear of the breech  3 . The breech  3 , valve passage  8  rearward of the valve slider  39 , and all contiguous cavities not isolated by seals within the housing  1  may here be recognized as the intermediate reservoir discussed in the background of the invention. The bolt  28  will remain approximately at rest, where its position will only adjust slightly to allow more or less gas through the bolt rest-point passage  10  as required to maintain a balance of pressure and spring forces on it while the pressure continues to increase. 
     Shown in  FIG. 18E , once the pressure in the valve passage  8  rearward of the valve slider  39  has increased sufficiently to overcome the force of the valve spring  45  on the valve slider  39 , the valve slider  39  will be pushed forward until it contacts the valve bumper  44  if present, or valve passage cap  43  if no valve bumper  44  is present, thereby simultaneously stopping the flow of compressed gas from the source gas passage  12 , and allowing the flow of gas from the region of the breech  3  ahead of the bolt rear seal  36  through the feed passage, into the valve passage  8  rearward of the valve slider  39 , which is in communication with the region of the breech  3  behind the bolt  28 . 
     The bolt  28  is then driven forward by now unbalanced pressure and spring forces on its surface, pushing the projectile  61  forward in the barrel  4  and blocking the projectile feed passage  6 , preventing the entry of additional projectiles. When the bolt  28  reaches the position shown in  FIG. 18F , gas flows through the purge holes  30  in the spring guide  29 , through the center of the bolt  28 , and through the plurality of holes  27  on the front surface of the bolt  28 , which distribute the force of the flowing gas into uniform communication with the rear surface of the projectile  61 . 
     Shown in  FIG. 18G  and continued in  FIG. 18H , the action of the gas pressure on the projectile  61  will cause it to accelerate through and out of the barrel  4  and barrel extension  5 , at which time the barrel  4 , barrel extension  5 , breech  3 , valve passage  8  rearward of the valve slider  39 , and all communicating passages which are not sealed will vent to atmosphere. 
     When the pressure within the valve passage  8  rearward of the valve slider  39  has been reduced to sufficiently low pressure such that the force induced on the valve slider  39  no longer exceeds that of the valve spring  45 , the valve slider  39  will begin to slide rearward. If the trigger  54  has not been allowed by the operator to move sufficiently far forward to allow the sear  40  to interfere with the rearward motion of the valve slider  39 , the valve slider  39  will continue to move rearward as described in Step  3 , and the cycle will begin to repeat, starting with Step  3 . If the trigger  54  has been allowed by the operator to move sufficiently far forward to allow the sear  40  to interfere with the rearward motion of the valve slider  39 , the valve slider  39  will push the sear  40  rearward into the preferred resting position and will come to rest against the sear  40  as shown in  FIG. 18H , and the cycle will proceed to Step  9  below. 
     Under the action of the bolt spring  32 , the bolt  28  will continue to move forward, compressing gas within the space ahead of the bolt rear seal  36  in so doing, and, allowing only a small gap by which the gas may escape into the valve passage  8 , the bolt  28  will be decelerated, minimizing wear on the bolt bumper  31  and stopping in its preferred resting position, at which point all components will now be in their original ready-to-fire configuration, shown in  FIG. 18A . 
     Cocking: 
     Whereas most compressed gas-powered projectile accelerators known to be in the art require a means of manual cocking, the compressed gas-powered projectile accelerator of the present invention will automatically cock when compressed gas, from a source mounted on any location on the housing  1  or other source, is introduced, preferably through a tube, attached to the source gas passage inlet  17 . If the compressed gas-powered projectile accelerator of the present invention is un-cocked (i.e., the valve slider  39  is not resting against the sear  40 , but further rearward under the action of the valve spring  45 ) when compressed gas is introduced through the source gas passage  12 , said gas will flow through the source passage  12 , valve passage  8 , and gas feed passage  9  into the region of the breech  3  ahead of the bolt rear seal  36 , and one of the semi-automatic or fully automatic cycles above described will ensue at Step  4 , the particular cycle being determined by the position of the mode selector cam  50 . The automatic cocking feature reduces potential contamination of the compressed gas-powered projectile accelerator of the present invention because said feature removes the necessity the additional perforation of the housing  1  to accommodate the connection of a means of manual cocking to internal components, which constitutes a common path by which dust and debris may enter the housing  1  of many compressed-gas powered projectile accelerators known to be in the art. 
     A means of manual cocking may be employed, but should be considered optional to the compressed gas-powered projectile accelerator of the present invention, as the addition of a means of manual cocking will allow the operator to bring the compressed gas-powered projectile accelerator of the present invention into a cocked state without cycling, and, more specifically, silently, without the audible report that will be associated with allowing the compressed gas-powered projectile accelerator of the present invention to automatically cock by completing a cycle. The simplest method of applying a manual cocking mechanism to the compressed gas-powered projectile accelerator of the present invention is shown in detail in  FIGS. 19 and 20 , where a knob  62  is attached, preferably by a screw  63 , to the valve slider  39 , which protrudes through a slot  64  in the housing  1 . However, because the presence of the slot  64  decreases the resistance to contamination and the cocking knob  62  increases wear on the valve slider  39  by not allowing it to freely rotate with respect to points of intermittent contact with the sear  40 , a preferred option is shown in  FIGS. 21 and 22 , where a manifold  65  attached to the housing  1  holds a cocking slider  66  which penetrates the housing  1  through a slot  64  such that the pushing forward of said cocking slider  66  will cause the valve slider  39  to move forward into a cocked position. The cocking slider manifold  65  obstructs the path of debris into the slot  64  in the housing  1 . A spring  67  biases the cocking slider  66  to remain out of the path of the valve slider  39  during operation. 
     The two examples provided are intended to be illustrative as it is to be appreciated that there are numerous methods by which a means of manual cocking (such as the addition of any appendage to the valve slider  39  which may be manipulated from the housing  1  exterior, particularly by protrusion from the front or rear of the valve passage  8 ) may be incorporated into the projectile accelerator of the present invention without altering the inventive concepts and principles embodied therein. 
     Expansion Chamber or Second Regulator in Source Gas Passage  12 : 
     One distinct advantage of this preferred embodiment of the compressed gas-powered projectile accelerator of the present invention is that, because the housing  1  can preferably made from a single piece of material, a feed gas conditioning device can easily be incorporated into the housing  1 , preferably inserted into the expanded section of the source gas passage  16 , shown in detail in  FIG. 23 , whereas for compressed gas-powered projectile accelerators known to be in the art, such devices are typically contained in separate housings which are typically either screwed into or welded to the primary housing. 
     In  FIG. 24  the source gas passage  12  of the compressed gas-powered projectile accelerator of the present invention is shown in detail with the option of baffle inserts  68  within the expanded section of the source gas passage  16  to reduce the potential for liquid to enter the valve passage  8 . A spring  69  placed between the lowest baffle insert and a fitting  70  installed at the source gas passage inlet  17  acts to retain the baffle inserts  68  in position. 
     In  FIG. 25  the source gas passage  12  of the compressed gas-powered projectile accelerator of the present invention is shown with the option of an additional feed gas regulator inserted into the expanded section of the source gas passage  16 , where a spring  71  pushes a preferably cylindrical and preferably beveled slider  72 , perforated with a plurality of holes, against a matching seat  73 , which is sealed against the wall of the expanded section of the source gas passage  16  by arbitrary means, and exemplified by o-ring/groove type seals  74  in  FIG. 25 . The position of the seat  73  is maintained by threads engaging the wall of the expanded section of the source gas passage  16 , which is correspondingly threaded, and rotation of the seat  73  (which has a hexagonally shaped groove designed to match a standard hexagonal key wrench), causing it to thread more or less deeply into the expanded section of the source gas passage  16 , allows adjustment of the spring  71  tension, thereby adjusting the equilibrium downstream (spring  71  side) pressure. 
     Pneumatically Assisted Feed: 
     In  FIGS. 26-29  the compressed gas-powered projectile accelerator of the present invention with the option of an added pneumatic feed-assist tube  75  which re-directs a preferably small portion of gas from the breech  3  to increase the bias of projectiles to enter the barrel  4  is shown used in conjunction with a gravitationally induced bias. The pneumatic feed-assist tube  75  can increase the rate of entry of projectiles into the barrel  4 , allowing the cycle to be adjusted to higher rates than is possible without the addition of said pneumatic feed-assist tube  75 . The pneumatic feed-assist tube  75  may be attached in such a way to communicate with any point in any passage within the compressed gas-powered projectile accelerator of the present invention, the shown preferred position being exemplary, and may optionally be incorporated as an additional passage within the housing. The amount of gas which is redirected can be metered by the internal cross-sectional area of the pneumatic feed-assist tube  75  and/or connecting fittings  76 ,  77 , and/or by optional adjustable valving integrated into the pneumatic feed-assist tube  75  and/or connecting fittings  76 ,  77  (not shown for clarity). 
     Alternate Bolt Resting Positions: 
     While the preferred embodiment of the compressed gas-powered projectile accelerator of the present invention has been shown depicting the preferred resting position of the bolt  28  in its most forward travel position because this takes advantage of the bolt  28  to prevent the entry of more than one projectile into the barrel  4  between cycles, it is to be appreciated that small changes in the configuration of the bolt  28 , bumpers  31 ,  38 , and bolt spring  32  can cause the bolt  28  to rest in a different location between cycles without changing the basic operation of the compressed gas-powered projectile accelerator of the present invention. If the bolt spring  32  is placed in front of the larger diameter section of the bolt  28 , instead of behind as in  FIG. 3 , the bolt  28  will be biased to rest against the breech cap bumper  38  at the rear of the breech  3  between cycles. Alternatively, a combination of springs, one ahead and one behind the larger diameter section of the bolt  28 , may be used to bias the bolt  28  toward any resting position between cycles, depending on the length and relative stiffness of the two springs. Changes in the resting position of the bolt  28  will alter the initial motion of the bolt  28  which in all cases will move the bolt  28  toward the position described in Step  4  of both the semi-automatic and fully-automatic cycle descriptions with the bolt rear seal  36  just behind the front edge of the bolt rest-point passage  10 . Correspondingly, at the end of the last cycle, the bolt  28  will return to the altered rest position rather than the rest position described in the preferred embodiment. In all other respects, both semi-automatic and fully-automatic operation will be identical to as above described. If the bolt  28  is retained at rest in a position that does not prevent projectiles from entering the barrel  4  between cycles, some provision must be included to prevent projectiles from prematurely moving down the barrel  4 . This may be accomplished frictionally, by a close fit of projectiles to the barrel  4  diameter, or by the addition of a conventional spring biased retention device which physically blocks premature forward motion of projectiles in the barrel  4 . 
     Additional Cavities: 
     It is to be appreciated that the operating characteristics of the compressed gas-powered projectile accelerator of the present invention may be altered by the addition of supplementary cavities, either within the housing or attachments made to the housing, contiguous in any place with any of the internal passages of the apparatus without altering the inventive concepts and principles embodied therein. These cavities may be of fixed or variable volume. (Operating characteristics can be altered by changing the cavity volume.) An example of a compressed gas-powered projectile accelerator made according to the present invention with the addition of a variable volume is illustrated in  FIGS. 30 and 31 , where a threaded passage  78 , parallel and connected to the valve passage  8 , is closed at the rear by a threaded plug  79 , and at the front by a screw  80 , the position of which may be adjusted within the threaded passage  78  to vary the volume. In particular, the threaded passage  78  as shown in  FIGS. 30 and 31  may be connected to the valve passage  8 , as shown, or, alternatively, to the gas feed passage  9 , so that the gas volume may be varied in order to change the amount of acceleration applied to projectiles in lieu of, or in addition to, other means to control the same, already and to be further described. 
     Pneumatic Valve Slider Bias: 
     It is to be appreciated that the operating characteristics of the compressed gas-powered projectile accelerator of the present invention may be altered such that the bias of the valve slider  39  is induced by the pressure of compressed gas, rather than by a valve spring  45 , without altering the inventive concepts and principles embodied therein, as shown in  FIG. 32 , where the compressed gas-powered projectile accelerator made according to the present invention is shown in  FIG. 31  with the valve spring  45  omitted and the valve slider  39  geometry modified with an extension and pair of preferably o-ring type seals  81 ,  82  to allow the valve slider  39  to be pneumatically biased to move rearward when compressed gas is introduced into the volume  83  between the seals  81 ,  82 .  FIG. 32  depicts gas communication into this volume  83  to be through a fitting  84  threaded into a hole through the housing  1  as an example, but the routing of gas, preferably from the source connected to the source gas passage  12 , is arbitrary. The changes in the valve slider  39  geometry allow the valve slider bumper  44  to be placed inside the valve passage cap  43 , which is shown with a preferable o-ring type seal  85  to prevent gas leakage. Projectile velocity may be controlled either by regulation by arbitrary means (e.g., by a regulator within the expanded portion of the gas feed passage  16 , previously described, provided the gas is tapped downstream of the regulator) of the pressure in the volume  83  between of the valve slider seals  81 ,  82 , or by an adjustable volume, as previously described. Operation is as previously described except that the bias for the valve slider  39  to move rearward is provided by the pressure of gas within the volume  83  between of the valve slider seals  81 ,  82  rather than by a spring. 
     Electronic Embodiment of the Compressed Gas-Powered Projectile Accelerator of the Present Invention: 
     It is to be appreciated that the operating characteristics of the compressed gas-powered projectile accelerator of the present invention may be altered by the replacement of the valve and internal trigger mechanism components shown in the non-electronic preferred embodiment with electronic components without altering the inventive concepts and principles embodied therein, as shown in  FIGS. 33 and 34 . In  FIG. 34 , the valve and internal trigger mechanism components are shown replaced by a spring biased (toward the closed position) solenoid valve, consisting of a valve body  86 , valve slider  87  with seals  88 ,  89  (similar to the valve slider  39  in the nonelectronic preferred embodiment), spring  90 , coil  91 , and bumper  92 ; electronic switch  93 ; battery  94  (or other power source); and control circuit  95 ; where the opening force applied to the solenoid valve slider  87  by the coil  91  when energized by the control circuit  95  can be designed such that the pressure within the valve passage  8  rearward of the solenoid valve slider  87  will force the valve into the un-actuated position at the design set pressure, thus simultaneously terminating flow from the source gas passage  12  into the region of the breech  3  ahead of the larger diameter section of the bolt  28  and initiating flow from said region within the breech  3  ahead of the larger diameter section of the bolt  28  into the valve passage  8  rearward of the solenoid valve slider  87  and into the region of the breech  3  behind the bolt  28 , simulating the behavior of the mechanical system already described. The set pressure can be adjusted by adjusting the current in the solenoid valve coil  91 , thereby adjusting the projectile acceleration rate. Because velocity control is electronic, no velocity adjustment screw  46  need be incorporated into the valve passage cap  43 , and the valve passage cap  43  and corresponding bumper  44  need not be hollow. The control circuit  95 , preferably consists of an integrated circuit  96  which performs the cycle control logic, an amplifier  97 , a means of controlling valve coil  91  current, e.g. a variable resistor  98  with a “velocity control dial”  99  protruding to the exterior, and a multi-position switch  100  which can be used to disable the trigger  54  (one switch position), or select between semi-automatic (second switch position) and fully-automatic (third switch position) operation when the trigger  54  is pulled. With the exception of components replaced by the electronic control circuit  95  and solenoid valve components  86 ,  87 ,  88 ,  89 ,  90 ,  91 ,  92 , operation is identical to the non-electronic preferred embodiment (where the solenoid valve slider  87  performs the same role as the valve slider  39  in the non-electronic preferred embodiment). The battery  94  is shown preferably contained within a padded compartment  101  in the housing  1  with a preferably hinged door  102  to allow replacement. An optional mechanical safety cam  57 , identical to that employed on the non-electronic preferred embodiment of the compressed gas-powered projectile accelerator of the present invention, but differently located, is also shown in  FIG. 34 . 
     Alternatively, rather than relying upon the mechanical action of pressure within the valve passage  8  rearward of the solenoid valve slider  87  to push the solenoid valve slider  87  into the closed position, the solenoid valve coil  91  can be de-energized when the set pressure is reached, which can be determined based on timing, or by a signal supplied to the control circuit  95  by a pressure transducer  103  (or other electronic pressure sensor), which can be positioned in communication with the gas behind the solenoid valve slider  87  or in the breech  3  either ahead of or behind the largest diameter section of the bolt  28  (i.e. the intermediate reservoir), as shown in  FIGS. 35 and 36 , (through wires connecting the pressure sensor  103  to the control circuit  95 , the geometry of which are arbitrary and not shown in the Figures for clarity). In these cases, the velocity control dial  99  does not adjust the solenoid valve coil  91  current, but rather the timing, in the case of a timed circuit, or either the signal level from the pressure sensor  103  at which the control circuit  95  de-actuates the solenoid valve coil  91  or the said pressure sensor  103  signal, thereby accomplishing the same effect. 
     It is also to be appreciated that additional, optional controls can be incorporated into the control circuit  95  of the preferred electronic embodiment of the compressed gas-powered projectile accelerator of the present invention without altering the inventive concepts and principles embodied therein, such as additional switch  100  positions controlling additional operating modes where the projectile accelerator accelerates finite numbers of projectiles, greater than one, generally known as “burst modes” when the trigger  54  is pulled, as compared to semi-automatic operation, where a single projectile is accelerated per trigger  54  pull, and fully-automatic operation, where projectile acceleration cycles continue successively as long as the trigger  54  remains pulled rearward. Additionally, the timing between cycles can be electronically controlled, and said timing can be made adjustable by the inclusion of an additional control dial in the control circuit  95 . 
     In another embodiment of the present invention, shown in  FIGS. 37 ,  38  and  39 , a housing  104  has a forward end  105  shown to the left in the Figures and a rear end  107  shown to the right in the Figures. A preferably cylindrical passage forms a breech  106  contiguous with a barrel  108 . The breech may have a narrow diameter forward portion adjacent the forward end of the housing, and an expanded diameter rear portion adjacent the rear end of the housing, as shown in  FIG. 39 . 
     The barrel  108  may be extended by the addition of a barrel extension  110 , which is preferably a tubular member threaded or other wise attached into/onto barrel  108  at the front of the housing  104 . The barrel  108  is in communication with a projectile feed passage  112 , which may be defined in part by a projectile feed manifold  114  and further extending within the housing  104 . Projectiles  116  are introduced into the breech  106  via the projectile feed passage  112 . The projectile feed passage  112  may meet the barrel  108  at any angle whereby projectiles  116  can enter the breech  106 , but preferably is at least partially vertically oriented with respect to the housing to take advantage of gravity to bias the projectiles  116  into the barrel  108 . A means other than gravity may be employed to bias the projectiles into the housing, such as a spring mechanism. The projectile feed passage  112  may be connected such that its center axis intersects the center axis of the barrel  108 , as shown in  FIG. 40 , or the projectile feed passage  112  center axis can be offset from the center axis of the barrel  108 , as long as the intersection forms a hole sufficiently sized for the passage of projectiles  116  from the projectile feed passage  112  into the barrel  108 . 
     Preferably parallel to the barrel  108  and breech  106  is a preferably cylindrical gas distribution passage  118 , in communication with the breech  120  via an upper gas feed passage  120 , and further in communication with a preferably cylindrical valve passage  122  by a lower gas feed passage  124  and valve locking shaft  126 . The gas distribution passage  118  may be closed at the front of the housing  104  by a plug, or, as shown in  FIGS. 3 and 4 , by a throttling screw  128  optionally incorporating an o-ring/groove type seal around its outer edge (not shown). 
     A feed-assist shaft  130  extends upwardly into the projectile feed manifold  134 , and connects with a feed-assist jet  132 . Alternatively, the feed-assist shaft  130  can also be connected to the feed-assist jet  132  by a tube  138  routed externally to the projectile feed manifold  134 . The throttling screw  128  controls gas flow between the gas distribution passage  118  and the feed assist shaft  130 . More particularly, the degree to which the throttling screw  130  partially or completely blocks the intersection of a vertical feed-assist shaft  130  and the gas distribution passage  118  is dependent upon the depth to which the throttling screw  128  has been threaded into the gas distribution passage  118 . Of course, if there is no desire to use the gas from the gas distribution passage  118  to assist feeding projectiles  116 , the throttling screw  128 , feed-assist shaft  130  and feed-assist jet  132  may be removed. 
     The gas distribution passage  118 , feed-assist shaft  130 , and feed-assist jet  132  are shown in the same plane as the barrel  108 , breech  106 , and valve passage  122  centerlines in  FIG. 39  for simplicity of interpretation. However, it is preferred that these components be positioned away from the centerline of the housing  104  to facilitate a more compact arrangement and simplify the intersection of the feed-assist shaft  130  with the gas distribution passage  118  and feed-assist jet  132 , by providing an envelope for a straight vertical path beside the barrel  108 , as illustrated in  FIGS. 40-43 . This simplifies the manufacture of the connecting passages  124 ,  128 ,  130 , as shown in  FIG. 40 ,  FIG. 41 ,  FIG. 42 , and  FIG. 43 , where the connecting passages  124 ,  128 ,  130  are shown drilled from the side of the housing  104  through test ports closed with plugs  134 . The test ports closed with plugs  134  are optional because they are not required for correct function of the compressed gas-powered projectile accelerator, and may be eliminated from the design by a variety of means, such as closure by welding, use of special tooling to allow manufacture from the interior, etc. 
     Also for ease of understanding, the gas distribution passage  118  is not depicted extending to the rear of the housing  104  in  FIG. 39 . However, for manufacturing simplicity, provided that it is staggered so as to not intersect the bolt rest-point slot, discussed in further detail below, the gas distribution passage  118  may extend to the rear of the housing  104  and be either closed by a simple plug or a throttling screw applied to the intersection with the lower gas feed passage  124  in similar fashion to the intersection with the feed-assist shaft  130 . The inclusion of one (as shown) or more optional ports  142  to vent feed-assist jet  132  gas once a projectile  116  is in the barrel  108  is illustrated in  FIG. 44 . 
     The valve passage  122  is also in communication with the breech  106  via a bolt rest-point slot  136 . A source gas passage  140  is also in communication with the bolt rest-point slot  136 . A trigger cavity  142  may also be in communication with the bolt rest-point slot  136 . The trigger cavity  142  is perforated in several places to allow extension of control components to the exterior of the housing  104 . 
     The source gas passage  140  is preferably valved, such as by means of a screw  144 , the degree to which partially or completely blocks the source gas passage  140  depending upon the depth to which the screw  144  is threaded into the housing  104  so as to intersect the source gas passage  140 . Alternatively, the lower gas feed passage  124  or upper gas feed passage  120 , may be similarly valved instead of, or in addition to, the source gas passage  140  to control flow both between the source gas passage  140  and breech  106 , and between the source gas passage  140  and valve passage  122 . The screw  144  should form a seal with the hole in which it sits, preferably by the use of one or more o-rings in grooves  146 . 
     The source gas passage  140  may include an expanded section  148  to minimize liquid entry and maximize consistency of entering gas by acting as a plenum. Gas is introduced through the source gas passage inlet  150  at the base of the housing  104 , which may be designed to accept any high pressure fitting. A gas cylinder acting as a source of compressed gas (not shown), may be mounted to the housing  104 , preferably to the base of the housing  104  in front of the optional trigger guard  152  illustrated in  FIG. 39 . Alternately, the gas cylinder may be mounted to the rear of the source gas passage inlet  150 , and/or may be connected to said inlet  150  through a flexible high pressure hose. The source gas passage  140  is depicted as integrated into the lower rear part of the housing  104  to facilitate manufacture of the housing  104  from a single piece of material. However, it should be appreciated that any configurations of the source gas passage  140 , whether within the housing  104  or as an attachment to the housing  104 , may be substituted for the illustrated embodiment. 
     A hollow slider or bolt  154  is slidably disposed within the barrel. The bolt  154  preferably has a cylindrical shape that substantially mates with the cylindrical shape of the barrel  108 . The bolt  154  is preferably rotatable within the barrel  108  and breech to minimize wear, and is preferably formed from a single piece. The bolt  154  is slidable within the barrel  108  and breech  106  between a forward or first position and a rearward or second position. The bolt  154  has an aperture therethrough for allowing the passage of gas. The bolt  154  may be adapted to move coaxially about a preferably cylindrical spring guide  156  which may be extended within the aperture of the bolt  154 . The spring guide  156  has a hollow space at the forward end communicating with at least one or, as shown, a plurality of purge holes  158  about its circumference. A preferably resilient bolt bumper  160  is attached to the bolt  154  at a point where the bolt  154  changes diameter and meets a narrowed portion of the housing, limiting the bolts  154  forward travel and easing shock in the event of malfunction. The bolt bumper may be an o-ring as shown which acts both as a bumper and as a seal between the bolt  154  and the walls of the breech  106 . 
     A bolt spring  162  surrounds the spring guide  156 . The spring guide  156  is mounted to a removable breech cap  166 . As illustrated, the spring guide  156  may be held in place by a cylindrical cavity in the cap  166  by means of a step in its diameter, and trapped by a screw  164 . A spring guide bumper  168 , such as an o-ring, may placed between the end of spring guide  156  and the breech cap  166 . 
     The bolt  154  and spring guide  156  are shown with o-ring/groove type gas seals  170 ,  172 ,  174 , to prevent leakage. However, various types of seals may be substituted for the illustrated o-rings. Optionally, an additional o-ring/groove type gas seal  176  may be placed at the front tip of the bolt  154 . A cylindrical resilient bumper  178  which may be mounted between the bolt  154  and breech cap  166 , partially surrounding the bolt  154  and spring guide  156 , to protect the bolt  154  and breech cap  166  in the event of malfunction. An o-ring/groove type gas seal  180  may be placed between the breech cap  166  and the wall of the breech to provide further sealing. 
     As shown in  FIG. 39 , a valve slider  182  with a first end adjacent the forward end of the housing, and a second end adjacent the rearward end of the housing, is slidable within the valve passage  122  from a first position adjacent the forward end of the housing, to a second position adjacent the rearward end of the housing. The valve slider may be partially hollow adjacent its first end and adapted for receiving a valve spring  196 . 
     The valve slider may be formed having a first enlarged portion  189  adjacent the second end of the of the valve slider  182 , and a second enlarged portion  191 , forward of the first enlarged portion  189 , as shown in detail in  FIG. 45 . In a preferred embodiment, the valve slider  182  forms or includes seals  186 ,  188 ,  190  with the valve passage  122  at a plurality of points. For example, in the Figures, three points are shown for illustration where single o-ring/groove type seals  186 ,  188 ,  190  provide sealing, but multiple o-rings or any other appropriate method of sealing may be used, for example, use of a flexible material such as polytetrafluoroethylene at the sealing points may be used to form surface-to-surface seals in lieu of o-rings, and can potentially reduce wear on the seals  186 ,  188 ,  190 . An optional bumper  192  to minimize wear is shown threaded into a hole in the rear face of the valve slider  182  in  FIG. 39 , and a bumper  194 , optionally an o-ring, is shown at a step in the valve slider  182  diameter to minimize wear and reduce noise due to interaction with the housing  104 . 
     A valve spring  196  located adjacent the first end of the valve passage  122  and, preferably, partially within the valve slider  182 . The valve spring is positioned between the valve slider  182  and a valve spring guide  198 . The valve spring  196  biases the valve slider  182  toward its second position. The valve spring guide  198  may be held in place by a velocity adjustment screw  200  preferably threaded into the valve passage  122 . The position of the screw may be adjusted to increase or decrease tension in the valve spring  196 , thereby adjusting the operating pressure of the cycle and magnitude of projectile acceleration. The valve slider  182  may be held in its first position by a sear  184 , which can rotate about and slide on a pivot  202 . A sear spring  204  maintains a bias for the sear  184  to slide forward and rotate toward the valve slider  182 . Sliding movement of the sear  184  can be limited by means of a preferably cylindrical mode selector cam  206  which can slide along an axis parallel to the rotational axes of the sear  184  as previously described. 
     A trigger  208 , which rotates on a pivot  210 , is adapted to press upon the sear  184 , inducing rotation of the sear  184 . A bias of the trigger  208  to rotate toward the sear  184  (clockwise in  FIG. 39 ) is maintained by a spring  212 . Forward travel of the trigger  208  may optionally be limited by an adjustable forward trigger adjustment screw  214 , shown threaded into the trigger guard  152 . Rearward travel of the trigger is optionally adjustably limited by an optional rear trigger adjustment screw  216 , shown threaded into the housing  104 . It is to be appreciated that a number of means may be employed to adjust the trigger  208  movement for the compressed gas-powered projectile accelerator of the present invention without altering the inventive concepts and principles embodied therein. Rotation of the trigger  208  can also be limited by means of a preferably cylindrical sliding safety cam  218  as previously described. 
     It will be appreciated by one skilled in the art that the sliding of an o-ring/groove type rear valve slider seal  188 , shown in detail in  FIG. 45 , past the intersection of the valve passage  122  with the lower gas feed passage  124  will cause wear on the seal  188 , which may intermittently need replacement. One alternate configuration of the intersection between the valve passage  122  and lower gas feed passage  124  that is designed to reduce such wear is shown in  FIG. 46 . In this embodiment, the lower gas feed passage  124  intersects an enlarged portion  220  formed between a step in the valve passage  122  where the diameter of the valve passage changes, and an extension of the cocking assembly housing  222  (described below), is sealed to the wall of the valve passage  122  upstream of the bolt rest-point slot  136  by a preferably o-ring/groove type seal  224 . This forces the rear valve slider seal  188  to release pressure from all parts of its perimeter simultaneously, thereby avoiding asymmetric extrusion of the valve slider seal  188  into the lower gas feed passage  124 . Another configuration is shown in  FIG. 47 , where the rear valve seal  188  is comprised of a pair of o-rings, positioned such that the seal between the valve slider  182  and valve passage wall is made by a different o-ring on each side of the enlargement  220  of the valve passage  122 . The o-ring is positioned such that exactly one is always in contact with the wall of the valve passage  122  on one side of the enlargement  220  of the valve passage  122  or the other, thereby minimizing the wear on each and eliminating the brief gas flow around the rear valve slider seal  188  that occurs when the seal  188  moves across the lower gas feed passage  124  or enlargement  220  of the valve passage  122 , if present. In  FIG. 46  and  FIG. 47 , the enlargement  220  of the valve passage  122  is shown formed by a gap between a step in the valve passage  122  bore and the discreet cocking assembly housing  222  (described below). However, it should be appreciated that the enlargement  220  could be formed between a step in the valve passage  122  bore and an alternate part, such as a plug, replacing the discreet cocking assembly housing  222 , or as a feature in the valve passage  122  not involving a separate piece. 
     Discreet Cocking Module: 
     As described above, the compressed gas-powered projectile accelerator of the present invention will automatically cock when it is in an uncocked position when gas is supplied from a source of compressed gas to the source gas passage  140 . It is also desirable to provide some means of manual cocking. This can be accomplished by the addition of a discrete assembly, shown in  FIG. 39 , comprised of a preferably cylindrical hollow body  224  containing a preferably cylindrical plunger  226  partially surrounded and biased to move rearwardly by a cocking spring  228 . When not in use, the plunger  226  rests against and is contained within the cocking assembly housing  222  by interference with a hollow plug  230 . The hollow plug  230  is preferably threaded into the rear of the cocking assembly housing  222 . The hollow plug  230  has an inner diameter smaller than the largest section of the cocking plunger  226 , and may be penetrated by a section of the plunger  226  which can slide within the hollow plug  230 . The plunger  226  preferably forms a substantial seal with the body to minimized gas leakage. One suitable sealing mechanism is through use of an o-ring/groove type seal  232  located on the largest diameter section of the plunger  226 . It is also preferable that an o-ring/groove type seal  234  be incorporated into the cocking assembly housing  222  to form a seal with the housing  104 . Cocking is accomplished by depression of the portion of the cocking plunger  226  extending outward from the hollow plug  230 . The force of the depression overcomes the biasing provided by the spring  244 , thereby permitting the plunger  226  to push the valve slider  182  forward a sufficient distance to permit the sear  184  to engage the step in the valve slider  182  under the bias provided by the sear spring  246 . When pressure is removed from the cocking plunger  226 , the cocking spring  244  will bias the plunger  226  to its rearmost position, resting against the hollow plug  230 , where it will not interfere with motion of the valve slider  182  during operation. 
     Operation 
     Semi-Automatic Operation of the Compressed Gas-Powered Projectile Accelerator: 
     The preferred ready-to-operate configuration for semi-automatic operation is shown in  FIG. 39 , with the valve slider  182  in its first or cocked position, resting against the sear  184 , which, under the pressure of the valve spring  196  translated through the valve slider  182 , rests in its rearmost position. For operation, the safety cam  218  is positioned to allow the trigger  208  to rotate freely. The mode selector cam  206  is positioned so as to not restrict the forward movement of the sear  184 . The smaller diameters of the safety cam  218  and mode selector cam  206  are shown in this cross section, as said smaller diameters represent the portions of these components  218 ,  206  interacting with the trigger  208  and sear  184 , respectively. A projectile  116  is prevented from entering the barrel  108  by interference with the bolt  154 . 
     The trigger  208  is then pulled rearward, pulling the sear  184  downward, disengaging it from the valve slider  182 . The valve slider  182  may then be biased rearwardly to its second position by the valve spring  196 . 
     Under the force applied by the valve spring  196 , the valve slider  182  then slides rearwardly to its second position. It may be stopped by contact of its rear bumper with the cocking assembly housing  222 . When the valve slider  182  reaches its second position, it allows gas to enter the gas distribution passage  118  through the lower gas feed passage, flow through the gas distribution passage, and into the region of the breech  106  ahead of the bolt rear seal  172 . Compressed gas will necessarily also flow into the region of the valve passage  122  forward of the second enlarged portion  191  of the valve slider  182  adding pressure force to hold the valve slider  182  rearward in addition to the valve spring  196  bias. Simultaneously, the sear  184  is caused to slide forward and rotate (shown clockwise in the drawing) by the sear spring  246 , coming to rest against the valve slider  182  and, thus, disengaged from the trigger  208 . 
     The pressure of the gas against the bolt rear seal  172  causes the bolt  154  to slide rearward, until the bolt rear seal  172  passes the front edge of the bolt rest-point slot  136 , and reaches a preselected position, opening a flow path, and allowing compressed gas to pass into the bolt rest-point slot  136 , the valve passage  122  rearward of the valve slider  182 , and the region of the breech  106  behind the bolt  154 . A projectile  116  may then enter the barrel  108 , aided by gravity or some other force, and may be further aided by the suction induced by the motion of the bolt  154  rearward. Additional projectiles  116  in the projectile feed passage  112  are blocked from entering the barrel  108  by the projectile  116  already in the barrel  108 . The combined force of the bolt spring  162  and the pressure behind the bolt  154  bring the bolt  154  to rest, preferably without contacting the breech cap bumper  248  at the rear of the breech  106 . The bolt  154  will remain approximately at rest, where its position will only adjust slightly to allow more or less gas through the bolt rest-point slot  136  as required to maintain a balance of pressure and spring forces on it while the pressure continues to increase. 
     Once the pressure in the valve passage  122  rearward of the valve slider  182  has increased sufficiently to overcome the force of the valve spring  196  on the valve slider  182 , the valve slider  182  will be pushed forward until the front valve slider bumper  250  contacts the step due to the change in diameter of the valve passage  122 , thereby stopping the flow of compressed gas from the source gas passage  140 , and allowing the flow of gas from the region of the breech  106  forward of the bolt rear seal  172  and the region of the valve passage  122  forward of the enlarged portion of the valve slider  182  into the valve passage  122  rearward of the valve slider  182 , which is in communication with the region of the breech  106  rear of the bolt  154 . The sear  184 , under the action of the sear spring  246 , will rotate further (clockwise in the drawing) once the smaller diameter section of the valve slider  182  has traveled sufficiently far forward to allow this, coming to rest against the smaller diameter section of the valve slider  182 . 
     The bolt  154  is then driven forward by now unbalanced pressure and spring forces on its rear surface, pushing the bolt  154  and projectile  116  forward in the barrel  108  and blocking the projectile feed passage  112 , preventing the entry of additional projectiles  116 . When the bolt  154  has moved sufficiently far forward that the spring guide seal  174  enters the increased diameter hollow portion at the rear of the bolt  154 , disengaging the spring guide seal  174  from the bolt  154  internal bore, gas flows through the purge holes  158  in the spring guide  156  and through the aperture of the bolt  154 , to the rear surface of the projectile  116 . 
     The action of the gas pressure on the projectile  116  will cause it to accelerate through and out of the barrel  108  and optional barrel extension  110 , at which time the barrel  108 , barrel extension  110 , breech  106 , valve passage  122  rearward of the valve slider  182 , and all communicating passages which are not sealed will vent to atmosphere. 
     When the pressure within the valve passage  122  rearward of the valve slider  182  has been reduced to sufficiently low pressure such that the force induced on the valve slider  182  no longer exceeds that of the valve spring  196 , the valve slider  182  will slide rearward until its  40  motion is restricted by the sear  184 . The sear  184  will rest against the front of the trigger  208 , and may exert a (clockwise in drawing) torque helping to restore the trigger  208  to its  53  resting position, depending on the design of the position of the trigger pivot  210  relative to the point of contact with the valve slider  182 . 
     Under the action of the bolt spring  162 , the bolt  154  will continue to move forward, compressing gas within the space ahead of the bolt rear seal  172  in so doing, and, since there is only a small gap by which the gas may escape into the upper gas feed passage  120 , the bolt  154  will be decelerated, minimizing wear on the bolt bumper  160  and stopping in its preferred resting position. 
     When the trigger  208  is released, the action of the trigger spring  212 , sear spring  204 , and valve spring  196  will return the components to the preferred ready-to-fire configuration, as in Step  1  above. 
     Fully-Automatic Operation of the Compressed Gas-Powered Projectile Accelerator: 
     The preferred ready-to-operate configuration for fully-automatic operation is the same as described above for semi-automatic operation except that the mode selector cam  206  is positioned so as to restrict the forward travel of the sear  184 , i.e. with the largest diameter section of the mode selector cam  206  interacting with the sear  184 . 
     The trigger  208  is then pulled rearward, pulling the sear  184  downward, disengaging it from the valve slider  182 . 
     Under the force applied by the valve spring  196 , the valve slider  182  then slides rearward, until it is stopped by contact of its rear bumper with the cocking assembly housing  222 , allowing gas to flow into the region of the breech  106  ahead of the bolt rear seal  172  and into the region of the valve passage  122  ahead of the enlarged portion of the valve slider  182  (adding pressure force to hold the valve slider  182  rearward in addition to the valve spring  196  bias). The mode selector cam  206  prevents the sear  184  from sliding forward sufficiently far to disengage from the trigger  208 . 
     The pressure of the gas causes the bolt  154  to slide rearward, until the bolt rear seal  172  passes the front edge of the bolt rest-point slot  136 , allowing gas into the bolt rest-point slot  136 , valve passage  122  rearward of the valve slider  182 , rear passage, and region of the breech  106  behind the bolt  154 . The projectile  116  enters the barrel  108  either by gravity, a positive bias or a negative pressure, such as the suction induced by the motion of the bolt  154 . Additional projectiles  116  in the projectile feed passage  112  are blocked from entering the barrel  108  by the projectile  116  already in the barrel  108 . The combined force of the bolt spring  162  and the pressure behind the bolt  154  bring the bolt  154  to rest, preferably without contacting the breech cap bumper  248  at the rear of the breech  106 . The bolt  154  will remain approximately at rest, where its position will only adjust slightly to allow more or less gas through the bolt rest-point slot  136  as required to maintain a balance of pressure and spring forces on it while the pressure continues to increase. 
     Once the pressure in the valve passage  122  rearward of the valve slider  182  has increased sufficiently to overcome the force of the valve spring  196  on the valve slider  182 , the valve slider  182  will be pushed forward until the front valve slider bumper  250  contacts the step in the valve passage  122 , thereby simultaneously stopping the flow of compressed gas from the source gas passage  140 , and allowing the flow of gas from the region of the breech  106  ahead of the bolt rear seal  172  and the region of the valve passage  122  ahead of the enlarged portion of the valve slider  182  into the valve passage  122  rearward of the valve slider  182 , which is in communication with the region of the breech  106  behind the bolt  154 . 
     The bolt  154  is then driven forward by the now unbalanced pressure and spring forces acting on it, pushing the projectile  116  forward in the barrel  108  and blocking the projectile feed passage  112 , preventing the entry of additional projectiles  116 . When the bolt  154  has moved sufficiently far forward that the spring guide seal  36  enters the increased diameter hollow portion at the rear of the bolt  154 , disengaging the spring guide seal  36  from the bolt  154  internal bore, gas flows through the purge holes  158  in the spring guide  156  and through the center of the bolt  154 , into communication with the rear surface of the projectile  116 . 
     The action of the gas pressure on the projectile  116  will cause it to accelerate through and out of the barrel  108  and barrel extension  4 , at which time the barrel  108 , barrel extension  4 , breech  106 , valve passage  122  rearward of the valve slider  182 , and all communicating passages which are not sealed will vent to atmosphere. 
     When the pressure within the valve passage  122  rearward of the valve slider  182  has been reduced to sufficiently low pressure such that the force induced on the valve slider  182  no longer exceeds that of the valve spring  196 , the valve slider  182  will begin to slide rearward again. If the trigger  208  has not been allowed by the operator to move sufficiently far forward to cause the sear  184  to interfere with the rearward motion of the valve slider  182 , the valve slider  182  will continue to move rearward as described above, and the cycle will begin to repeat. If the trigger  208  has been allowed by the operator to move sufficiently far forward to allow the sear  184  to interfere with the rearward motion of the valve slider  182 , the valve slider  182  will push the sear  184  rearward into the preferred resting position and will come to rest against the sear  184 . 
     Under the action of the bolt spring  162 , the bolt  154  will continue to move forward, compressing gas within the space ahead of the bolt rear seal  172  in so doing, and, since there is only a small gap by which the gas may escape into the upper gas feed passage  120 , the bolt  154  will be decelerated, minimizing wear on the bolt bumper  160  and stopping in its preferred resting position, at which point all components will now be in their original ready-to-fire configuration. 
     Pre-Chamber to Independently Adjust First Cycle Rate from Subsequent Cycles: 
     A second throttling point upstream expanded section of the source gas passage  148 , can be formed by the addition of a throttling screw  236  with one or more preferably o-ring/groove type seals  238  about its diameter, threaded into a shaft  240  intersecting the source gas passage expanded section  148 , such that the degree of occlusion of the source gas passage expanded section  148  is adjustable by the depth to which the throttling screw  236  has been threaded, as shown in  FIG. 48 . By adjusting the upstream throttling screw  236  to be more restrictive to the flow through the source gas passage expanded section  148  than the downstream screw  144 , after the trigger  208  is pulled, gas flow past the downstream throttling screw  144  can be made to initially exceed that at the upstream throttling screw  236 , but will gradually decrease to the same amount as the pressure within the portion of the source gas passage  140 ,  148  between the throttling screws  150 ,  236  drops, at which point the flow will remain at a steady rate determined by the most restrictive of the two throttling  150 ,  236  (set to be the upstream throttling screw  236  as before stated). Because this will cause the chambers ahead of and behind the enlarged diameter portion of the bolt  154  to fill more quickly at first, and then gradually more slowly, the cycle rate will be most rapid on the first cycle, and then will slow on subsequent cycles, the number of cycles required to achieve a steady cycle rate, being determined by the volume and set positions of the throttling  150 ,  236 . 
     A preferred embodiment can be designed with the volume of the portion of the source gas passage  140 ,  148  between the throttling  150 ,  236  sized such that the downstream throttling screw  144  can be adjusted so that steady flow rate is established during the first cycle for a desired range of initial cycle times, thus allowing the position of the downstream throttling screw  144  to primarily adjust the time of the first cycle with all subsequent cycle times determined primarily by the position of the upstream screw  236 . Alternatively, similar slowing of the cycle rate can be accomplished with the downstream throttling screw  144  adjusted to be equally or more restrictive than the upstream throttling screw  236 ; however, in such cases, the initial and ultimately achieved steady flow rates will be dependent on the positions of both throttling  150 ,  236 , rather than the initial flow rate being primarily dependent upon the position of the downstream throttling screw  144  and the steady flow rate being primarily dependent upon the position of the upstream throttling screw  236 . 
     Mechanical Valve Locking: 
     A roller cam assembly, comprised of a rocker  242 , preferably holding a wheel  244  and pin assembly  246  (but it is to be appreciated that the replacement of the wheel  244  and pin  246  with a geometrically similar protrusion of the rocker  242  will not alter the inventive concepts and principles embodied herein), biased to rotate about a pivot  248  toward the valve slider  182  by a roller cam spring  250 , there engaging a detent in the valve slider  182  when in the rearmost position can be optionally included to mechanically increase the force required to push the valve slider  182  forward, as illustrated in  FIG. 49  and shown in detail in  FIG. 50  and  FIG. 51 . The roller cam assembly can be used in addition to, as shown, or in lieu of, the valve locking shaft  126  communicating gas ahead of the shoulder in the valve slider  182 . During operation, for the valve slider  182  to begin to move forward, the gas must supply sufficient pressure force on the valve slider  182  not only to compress the valve spring  196 , but to force the rocker to rotate against the roller cam spring  250  bias. Once the roller cam wheel  244  is fully disengaged from the detent in the valve slider  182 , the pressure in the valve passage  122  will now exceed that necessary to continue the motion of the valve slider  182  toward and maintain the valve slider  182  in its foremost position, having to compress the roller cam spring  250  no further. The valve slider  182  will be maintained in its foremost position until the pressure in the valve passage  122  has dropped below that necessary for the valve spring  196  to again move the valve slider  182  rearward. The roller cam spring  250  pushes against, and is retained by a screw  252 , which adjusts the tension in the roller cam spring  250  by the depth to which it is threaded into the housing  104 . By changing the tension in the roller cam spring  250 , the adjustment screw  252  can be used to adjust the amount of force required to push the valve slider  182  forward, thereby acting as an additional or substitute (to tensioning the valve spring  196 ) method of adjusting the set pressure of the compressed gas-powered projectile accelerator, thereby altering the projectile  116  velocity. 
     Valve Module with Integrated Cocking Button: 
     An alternate embodiment of the compressed gas-powered projectile accelerator is shown in  FIGS. 52-23 , comprised as before, but where the single piece housing  104  is replaced by three components comprised of an upper housing  254 , containing the barrel  108 , breech  106 , gas distribution passage  118  (again shown centered in the same plane as the barrel  108 , breech  106 , and valve passage  122  but preferably positioned away from the centerline of the upper housing  254  to facilitate a more compact arrangement and simple intersection with the feed-assist jet  132 , and also again optionally not depicted extending to the rear of the upper housing  254 ), and front half of the valve passage  122  as designated in the previous embodiment, hereafter denoted as the valve spring passage  256 ; a handle  258 , containing the trigger components and to which is connected the trigger guard  152 ; and a valve module housing  260 . The valve slider  182  is truncated to move primarily within a rear valve passage (corresponding to the rear half of the valve passage  122  in the previously described embodiment) within the valve module housing  260 , but with an extension into the valve spring passage  256  in contact with a separate hollow spring cup  264  sliding within the valve spring passage  256 , replacing the front portion of the valve slider  182  in the previous embodiment. 
     The truncated valve slider  182  is biased to move forward under the action of a valve slider/cocking plunger return spring  266  located within a cavity inside the truncated valve slider  182  and retained in position by the cocking plunger  226  sliding within the cavity within the valve slider  182 , the rear valve passage  262 , and the hollow retaining plug  230 . The valve slider/cocking plunger return spring  266 , which is less stiff than the valve spring  196 , serves only to maintain continuous contact between the valve slider  182  and valve spring cup  264 , and maintain a bias for the cocking plunger  226  to move rearward, supplanting the similar cocking spring  244  in the previous embodiment (which did not act on the valve slider  182 ). As in the previously described embodiment, the truncated valve slider  182  forms preferably o-ring/groove type seals at three places with the walls of rear valve passage  262  and it is to be appreciated that the previously described alternate configurations of the valve slider  182  and valve passage  122  shown in  FIG. 46  and  FIG. 47  can be equally applied to the valve slider  182  and rear valve passage  262  within the valve module housing  260  without altering the inventive concepts and principles embodied therein. 
     Cocking is accomplished by depression of the portion of the cocking plunger  226  protruding through the hollow retaining plug  230 , firstly causing it to slide forward into contact with the truncated valve slider  182  and subsequently pushing the truncated valve slider  182  and valve spring cup  264  forward with continued depression until the valve spring cup  264  has traveled sufficiently far to allow the sear  184 , acting under the bias of the sear spring  246 , to rotate clockwise into contact with the valve slider  182 , thereby preventing rearward return of the valve spring cup  264  when the cocking plunger  226  is allowed to return to its resting position under the bias of the valve slider/cocking plunger return spring  266  by engaging the rear face of the valve spring cup  264 . The valve slider/cocking plunger return spring  266  will also act to maintain the valve slider  182  in a forward position, resting against the valve spring cup  264 . 
     Several views of the valve module are shown in detail in  FIG. 60 ,  FIG. 61 ,  FIG. 62 , and  FIG. 63 . The interconnectivity of the rear valve passage  262 , gas distribution passage  118 , and breech  106  is identical to the previously described embodiment, but is accomplished at the interface between the valve module housing  260  and the upper housing  254 , rather than through test ports closed with plugs  134  from the side of the housing  104  as in the previously described embodiment. A slot  268  surrounded by a preferably o-ring/groove type seal  270  between the top face of the valve module housing  260  and the corresponding face of the upper housing  254  connects the upper gas feed passage  120 , lower gas feed passage  124 , valve locking shaft  126 , and a vertical shaft  272  intersecting the gas distribution passage  118 . A second preferably o-ring/groove type seal  274  surrounds the region of the valve module housing  260  upper face interfacing with the bolt rest-point slot  136  and a hole  276  providing connectivity to the region of the rear valve passage  262  behind the truncated valve slider  182 . 
     While the source gas passage  140  may be incorporated into the handle  258 , corresponding to its location in the housing  104  of previously described embodiment through a similar interface as between the valve module housing  260  and upper housing  254 , an alternate scheme is illustrated in  FIGS. 19-23 , where the source gas passage  140  is incorporated into the upper housing  254 , preferably parallel and opposite the gas distribution passage  118  with respect to the center plane (intersecting the barrel  108 , breech  106 , and valve spring passage  256  centerlines). As in the previous embodiment, the source gas passage  140  can include an expanded section  148  to minimize liquid entry and maximize consistency of entering gas by acting as a plenum. A vertical front source gas shaft  278  connects the source gas passage expanded section  148  to a preferably standard compressed gas bottle mount  280  via a preferably o-ring/groove type seal  282 , and, near the front and rear of the upper housing  254 , throttling  150 ,  236  with preferably o-ring/groove type seals  146 ,  238  control the flow area at the intersections of the source gas passage  140  (and/or the source gas passage expanded section  148 ) with the vertical front source shaft  272  and a vertical rear source gas shaft  284  extending from the horizontal source gas passage  140  in the upper housing  254  downward through a preferably o-ring/groove type seal between the upper housing  254  and the valve module housing  260  into the valve module housing  260 , to intersect a laterally oriented source gas shaft  288  connecting to the rear valve passage  262 , functioning similarly to the previously described embodiments. The lateral source gas shaft  288  extends to an access port  290  at the side of the valve module housing  260 , primarily an artifact of manufacture and shown blocked by a plug  292  threaded into the access port, but optionally replaceable with a pressure gauge or connectable to an alternate gas source. 
     It is to be appreciated that the seals  270 ,  274 ,  286  between the upper housing  254  and valve module housing  260  can be replaced by an alternate sealing scheme such as a single gasket without altering the inventive concepts and principles embodied therein. 
     The embodiment shown in  FIGS. 52-23  also employs a combined front bolt bumper ( 160  in the previous embodiment) and seal ( 170  in the previous embodiment), or bumper seal  294 , preferably an o-ring, which, in providing a stationary front bolt seal (not moving with the bolt  154 ), allows a reduction in the length of the breech  106  and bolt  154  by the distance required for the sliding seal  170  of the previously described embodiment to maintain continuous contact with the breech  106  wall. When not operating, and therefore not under pressure, the bumper seal  96  contact with the bolt  154  and internal surfaces of the breech  106  is maintained by pressure from the bolt  154 , biased to move forward by the bolt spring  162   30 . When the chamber formed between the step in the breech  106  and bolt  154  diameters is pressurized during operation, unlike in the previously described embodiment where the front bolt bumper  160  moves with the bolt  154 , the gas pressure will bias the bumper seal  96  to remain against the step in the breech  106  bore and the smaller bolt  154  outer diameter, thereby preventing gas from leaking around the bolt  154  toward the barrel  108  while the bolt  154  slides rearward, and therefore requiring no forward seal on the bolt  154 . The optional small, preferably o-ring/groove type seal  176  shown near the front tip of the bolt  154  does not aid in sealing gas within the chamber formed between the step in the breech  106  and bolt  154  diameters, but functions to minimize gas leakage rearward around the bolt  154  when vented into the barrel  108  through the bolt  154  to accelerate the projectile  116 . The front valve slider bumper and foremost valve slider seal  44  may similarly be replaced by a combined front valve slider bumper. 
     In addition to the valve spring cup  264 , the valve spring passage  256  contains identical components (velocity adjustment screw  49 , valve spring guide  198 , valve spring  196 ) to the front half of the valve passage  122  in the previously described embodiment. Because the valve spring  196  and valve slider/cocking plunger return spring  296  maintain constant contact between the valve spring cup  264  and truncated valve slider  182 , the valve spring cup  264  and truncated valve slider  182  move together, and act in the same fashion as the valve slider  182  of the previously described embodiment; thus function of the alternate embodiment illustrated in FIGS. is identical to that of the previously described embodiment for both semi-automatic and fully-automatic operation. 
     It is understood that the present invention is not limited to the particular embodiments shown and described herein, but that various changes and modifications may be made without departing from the scope and spirit of the invention.