Abstract:
A compressed gas powered gun provides recoil simulating the recoil of a gun firing gunpowder propelled projectiles. The valve assembly provides both consistent shot to shot pressure, and rearward gas pressure for generating recoil. Preferred embodiments of the compressed gas powered gun may include means for adjusting the amount of recoil provided. A trigger mechanism permitting semiautomatic operation, or full automatic operation at a user selectable cyclic rate, is provided. The air gun provides consistent gas pressure behind the projectile from shot to shot. A magazine and magazine indexing system for loading projectiles into the firing chamber in a manner contributing to the accuracy of the air gun is also provided.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional of U.S. patent application Ser. No. 09/756,891, entitled, “Compressed Gas-Powered Gun Simulating The Recoil of a Conventional Firearm,” filed Jan. 9, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This application relates to compressed gas powered guns. More specifically, the invention relates to training guns duplicating various characteristics of guns firing gunpowder propelled projectiles.  
           [0004]    2. Description of the Related Art  
           [0005]    Guns firing projectiles propelled by compressed air or gas are commonly used for recreational target shooting or as training devices for teaching the skills necessary to properly shoot guns firing gunpowder propelled projectiles. Ammunition for air guns is significantly less expensive than gunpowder propelled ammunition. A typical gas powered projectile has significantly lower velocity and energy than a gunpowder propelled projectile, making it much easier to locate a safe place to shoot an air gun, and much less expensive to construct a suitable backstop. Additionally, the low velocity and energy of air powered projectiles makes air guns significantly less useful as weapons than guns firing gunpowder propelled projectiles. Lack of usefulness as a weapon is an important factor in making air guns available in regions where national or local governments regulate firing gunpowder propelled projectiles (firearms).  
           [0006]    To be an effective training tool, an air gun must duplicate the characteristics of a firearm as closely as possible. These characteristics include size, weight, grip configuration, trigger reach, type of sights, level of accuracy, method of reloading, method of operation, location of controls, operation of controls, weight of trigger pull, length of trigger pull, and recoil. The usefulness of a gas powered gun as a training tool is limited to the extent that any of the above listed characteristics cannot be accurately duplicated.  
           [0007]    Presently available air guns increasingly tend to have an exterior configuration resembling that of a gun firing a powder propelled projectile. Presently available air guns may be used in a semi-automatic (one shot per pull of the trigger) or very rarely full automatic (more than one shot per pull of the trigger) mode of fire, although the cyclic rate of full automatic fire typically does not duplicate the cyclic rate of a full automatic firearm firing a projectile powered by gunpowder. The vast majority of presently available airguns which are advertised as being semiautomatic are actually nothing more than double-action revolver mechanisms disguised within an outer housing that simply looks like a semiautomatic gun. However, because they are true double-action mechanisms, the weight of trigger pull is much heavier than the weight of trigger pull of the present invention, which has a true single-action trigger. Presently available air guns have also been designed to simulate the trigger pull and reloading of guns firing gunpowder propelled projectiles.  
           [0008]    Presently available air guns do not duplicate the recoil of a gun firing a powder propelled projectile. The inability to get a trainee accustomed to the recoil generated by conventional firearms is one of the greatest disadvantages in the use of air guns as training tools. Additionally, although presently available air guns can be made extremely accurate, variations in gas pressure can cause differences in shot placement from shot to shot, or from the beginning of a gas cartridge to the end. Further, duplication of the cyclic rate of a conventional firearm within an air gun would enable a trainee to learn how to properly depress the trigger to fire short bursts of approximately three shots in full automatic mode of fire using an air gun. Because recoil is significantly more difficult to control during full automatic fire than during semi-automatic fire, an air gun simulating both recoil and the cyclic rate of a conventional firearm would be particularly useful as a training tool.  
           [0009]    Accordingly, there is a need for an air powered gun duplicating the recoil of a conventional firearm. Additionally, there is a need for an air powered gun maintaining a consistent compressed gas pressure behind the projectile from shot to shot, thereby maintaining a constant velocity, energy, and point of impact for each projectile. Further, there is a need for an air gun duplicating the full automatic cyclic rate of a conventional full automatic firearm. There is also a need to combine these characteristics into an air gun that is not particularly useful as a weapon, thereby facilitating safe use by inexperienced trainees, making training facilities easier and more economical to construct, lowering the cost of ammunition and training, reducing noise levels, and broadening the legality of ownership.  
         SUMMARY OF THE INVENTION  
         [0010]    The preferred embodiment of the invention is an air or gas powered gun providing a recoil similar to that of a gun firing a powder propelled projectile. The compressed gas powered gun includes an improved magazine and magazine indexing system, contributing to the accuracy of the gun. The compressed gas powered gun preferably also duplicates many other features of a conventional firearm, for example, the sights, the positioning of the controls, and method of operation. One preferred embodiment simulates the characteristics of an AR-15 or M-16 rifle, although the invention can easily be applied to simulate the characteristics of other conventional firearms.  
           [0011]    The operation of a compressed gas powered gun of the present invention is controlled by the combination of a trigger assembly, bolt, buffer assembly and valve. Preferred embodiments will be capable of semi-automatic fire, full automatic fire at a low cyclic rate, and full automatic fire at a high cyclic rate. One of the two full automatic cyclic rates preferably approximately duplicates the cyclic rate of a conventional automatic rifle, for example, an M-16 rifle.  
           [0012]    The trigger assembly includes a trigger having a finger-engaging portion and a selector-engaging portion, a selector switch, a trigger bar, a sear trip, and a sear. The selector switch will preferably by cylindrical, having three bearing surfaces corresponding to safe, semi-automatic fire, and full automatic fire at a low cyclic rate, and a channel corresponding to full automatic fire at a high cyclic rate. These surfaces and channel of the selector bear against the selector engaging portion of the trigger, permitting little or no trigger movements if safe is selected, and increasing trigger movement for semi-automatic fire, low cyclic rate full automatic fire, and high cyclic rate full automatic fire, respectively. The sear is mounted on a sliding pivot, and is spring-biased towards a rearward position. The sear has a forward end for engaging the sear trip, and a rear end for engaging the bolt. The bolt preferably contains a floating mass, and reciprocates between a forward position and a rearward position. Although the bolt is spring-biased towards its forward position, the bolt will typically be held in its rearward position by the sear except during firing.  
           [0013]    The valve assembly includes a reciprocating housing containing a stationary forward valve poppet, a sliding rear valve poppet, and a spring between the front and rear valve poppets. The spring pushes the rear valve poppet rearward, causing the rear poppet to bear against the housing, thereby closing the rear valve and pushing the housing rearward. Pushing the housing rearward causes the housing to bear against the front valve poppet, thereby closing the front valve.  
           [0014]    Before the trigger is pulled, the trigger is in its forwardmost position, the bolt is held to the rear by its engagement with the sear, and the sear, although spring-biased rearward, is pushed towards its forwardmost position by the bolt. Pulling the trigger causes the trigger bar to move rearward, pivoting the sear trip upward. The upward movement of the sear trip pushes upward on the forward end of the sear, causing the rearward end of the sear to move down. The bolt is then free to travel forward, where the bolt strikes the rear valve, thereby moving the rear valve relative to the housing and opening the rear valve. Air pressure between the O-ring on the bolt face and the O-ring on the rear of the valve housing causes the housing to move forward, thereby opening the forward valve. Opening the forward valve dispenses pressurized gas to a position directly behind the projectile, causing the projectile to exit the barrel. Opening the rear valve supplies air pressure to the bolt face, thereby causing the bolt to return to its rearward position. If semi-automatic fire is selected, the limited movement of the sear trip, combined with the rearward spring-bias on the sear, causes the sear to move backwards on its pivot to a position where the sear trip can no longer apply upward pressure to the forward portion of the sear. The rear portion of the sear therefore pivots upward. The bolt will be propelled rearward to a point slightly behind the position wherein it engages the sear. As the bolt returns forward, the sear, which is no longer held in place by the sear trip, will engage the bolt, preventing further forward movement. From this position of the components, the trigger must be released before it can be pulled to fire another shot.  
           [0015]    If full automatic fire at a slow cyclic rate is selected, the trigger may be pulled slightly farther to the rear before it engages the selector, thereby causing the sear trip to pivot slightly higher. Whereas the upper bearing surface of the sear trip pushes the sear up to initially release the bolt, here, the lower end bearing surface of the sear trip pushes the sear up sufficiently so that, when the bolt catches the sear, there is only about {fraction (1/32)} nd  inch of engagement between the sear and bolt. The floating mass bolt is thereby momentarily held in its rearward position by the sear, which cams forward off the sear trip as the forward motion of the bolt pushes the sear from its rearward position to its forward position.  
           [0016]    If full automatic fire at a high cyclic rate is selected, the trigger is allowed to travel to its maximum rearward position. The sear trip is thereby pivoted upward to its maximum extent, causing the lower end bearing surface of the sear trip to push the sear completely out of the way of the bolt. Therefore, as soon as the spring behind the bolt driver overcomes the rearward momentum of the bolt, the bolt will simply return forward and again actuate the valve.  
           [0017]    A compressed gas powered gun of the present invention preferably includes a magazine and magazine indexing assembly configured to facilitate precise alignment of the firing chambers with the barrel. A preferred embodiment of the magazine is a cylinder. The term “cylinder” as used herein does not necessarily mean a perfect geometrical cylinder, but is used to denote a generally cylindrical magazine wherein a plurality of firing chambers are located around its circumference, as known to those skilled in the art of revolvers. A preferred cylinder will have six chambers, although this number may vary. The exterior surface of the cylinder will preferably include a plurality of flutes, with the flutes located between the chambers, and with an equal number of chambers and flutes. One preferred embodiment of the cylinder aligns the chamber with the barrel in the three o&#39;clock position when viewed from the rear or the nine o&#39;clock position when viewed from the front. A spring-biased bearing preferably engages the flutes, thereby precisely aligning the cylinder with the barrel. A preferred bearing will have a larger radius than the radius of the flutes, thereby maximizing the precision with which the chamber and barrel may be aligned. This arrangement permits the barrel and chamber to be aligned with such precision that a forcing cone is not needed at the breach of the barrel.  
           [0018]    Indexing of the cylinder is controlled by the forward and backward movements of the bolt. A spring-biased pawl mounted on a pawl carrier is located directly behind the cylinder. The pawl carrier reciprocates between a left most position and a right most position, with the left most position corresponding to the engagement of the pawl with one chamber of the cylinder, and the right most position corresponding to engagement of the pawl with another chamber of the cylinder. An operating rod extends forward from the bolt, overlapping the pawl carrier. The bottom surface of the operating rod includes an angled slot, dimensioned and configured to guide an upwardly projecting pin on the pawl carrier. With the bolt in its rear most position, the pawl carrier pin is located in the forwardmost portion of the operating rod&#39;s angled slot. The pawl carrier and pawl are therefore in their right side position. The pawl is spring-biased forward to engage the chamber in the one o&#39;clock position when viewed from the rear, or the eleven o&#39;clock position when viewed from the front. As the operating rod moves forward due to forward travel of the bolt, the pawl carrier is moved from its right side position to its left side position. The left side of the pawl includes a ramped surface which permits the pawl to be pushed rearward by the cylinder wall, against the bias of the spring, allowing the pawl to move from the top right side chamber to the top left side chamber. When the bolt returns to its rearward position, the pawl and pawl carrier are moved from their left side position to their right side position. The right side of the pawl is parallel to the inside of the cylinder wall, so that movement of the pawl from left to right will cause the cylinder to index in a clockwise direction when viewed from the rear, or a counterclockwise direction when viewed from the front. The bearing will be biased out of the current flute, and will bear against the next flute at the completion of indexing, thereby properly aligning the next firing chamber with the barrel.  
           [0019]    Another preferred embodiment includes a tubular magazine in addition to the cylinder. The tubular magazine is aligned with one chamber of the cylinder whenever another chamber of the cylinder is aligned with the barrel. The tubular magazine includes a spring-biases follower for pushing projectiles rearward into the cylinder. Whenever the cylinder is indexed, another projectile will thereby be pushed into an empty chamber of the cylinder as that chamber is aligned with the tubular magazine.  
           [0020]    If no tubular magazine is present, or if use of only the cylinder is desired, a preferred method of reloading the compressed gas powered gun is to remove the cylinder, place a single pellet into each chamber, and then replace the cylinder. If the tubular magazine is used, a preferred method of loading the compressed gas powered gun includes retracting the follower using a finger tab secured to the follower and extending outside the gun, opening a loading gate, and pouring projectiles into the tubular magazine. Preferred projectiles for use of a tubular magazine include spherical pellets. Preferred projectiles for use with the cylinder alone include spherical pellets or conventional air gun pellets.  
           [0021]    A compressed gas powered gun of the present invention uses a recoiled buffer system for biasing the bolt forward, and for providing a recoil for the shooter. A preferred buffer system includes a floating mass bolt driver, and an air resistance bolt driver, with a spring disposed therebetween. This assembly is located in a tube within the air gun&#39;s shoulder stock, which is preferably a cylindrical tube. The buffer assembly may be oriented so that either the air resistance bolt driver or the floating mass bolt driver is positioned directly behind the bolt, with the other bolt driver placed at the rear of the stock. The forward bolt driver will thereby abut the rear of the bolt, pushing the bolt forward.  
           [0022]    If the air resistance bolt driver is positioned directly behind the bolt, light recoil results. The air resistance bolt driver has less mass than the floating mass bolt driver, resulting in less mass reciprocating back and forth. Additionally, the air resistance bolt driver will trap air behind it as it reciprocates, thereby slowing travel of the reciprocating mass. Conversely, positioning the floating mass bolt driver behind the bolt results in heavier recoil, due to the increased reciprocating mass and the lack of the ability of the floating mass bolt driver to trap air. The shooter may therefore select the desired level of recoil to correspond with the recoil of the conventional firearm the shooter wishes to simulate.  
           [0023]    It is therefore an aspect of the present invention to provide a compressed gas powered gun simulating the recoil of a conventional firearm.  
           [0024]    It is another aspect of the present invention to provide a compressed gas powered gun wherein the level of recoil provided to the shooter may be selected by the shooter.  
           [0025]    It is further aspect of the present invention to provide a compressed gas powered gun capable of simulating the operation of a conventional firearm.  
           [0026]    It is another aspect of the present invention to provide a compressed gas powered gun capable of both semi-automatic and full automatic operation.  
           [0027]    It is a further aspect of the present invention to provide a compressed gas powered gun wherein different cyclic rates of full automatic fire may be utilized.  
           [0028]    It is another aspect of the present invention to provide a compressed gas powered gun utilizing a magazine and magazine indexing system providing precise alignment of the firing chambers with the barrel.  
           [0029]    It is a further aspect of the present invention to provide a compressed gas powered gun capable of utilizing multiple types of projectiles.  
           [0030]    It is another aspect of the present invention to provide a compressed gas powered gun for providing training that accurately simulates shooting a conventional firearm.  
           [0031]    It is a further aspect of the present invention to provide a compressed gas powered gun that may be legally owned and utilized in locations where conventional firearms are heavily restricted.  
           [0032]    Theses and other aspects of the present invention will become apparent through the following description and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0033]    [0033]FIG. 1 is a side view of a compressed gas powered gun according to the present invention.  
         [0034]    [0034]FIG. 2 is a side view of a four-position selector switch according to the present invention.  
         [0035]    [0035]FIG. 3 is a side view of a four-position selector switch according to the present invention, rotated 90° from the position of FIG. 2.  
         [0036]    [0036]FIG. 4 is a side cross-sectional view of a trigger assembly, valve assembly and bolt of a gas powered gun according to the preset invention, showing the position of the components before the trigger is pulled.  
         [0037]    [0037]FIG. 5 is a side cross-sectional view of a trigger assembly, valve assembly, and bolt of a gas powered gun according to the present invention, showing the position of the components at the moment of firing.  
         [0038]    [0038]FIG. 6 is a side cross-sectional view of a trigger assembly, valve assembly, and bolt of a gas powered gun according to the present invention, showing the position of the parts after firing and with the trigger still depressed during semi-automatic fire.  
         [0039]    [0039]FIG. 7 is a side cross-sectional view of a trigger assembly, valve assembly, a bolt of a gas powered gun according to the present invention, showing the position of the components after the bolt has returned and with the trigger still pulled during full automatic fire at a slow cyclic rate.  
         [0040]    [0040]FIG. 8 is a side cross-sectional view of a trigger assembly, valve assembly and bolt of a gas powered gun according to the present invention, showing the position of the components with the bolt retracted and trigger depressed during full automatic fire at a high cyclic rate.  
         [0041]    [0041]FIG. 9 is a top cross-sectional view of one preferred embodiment of a magazine assembly for a gas powered gun according to the present invention, showing the location of the components when the bolt is in the forward position.  
         [0042]    [0042]FIG. 10 is a top cross-sectional view of a magazine assembly of FIG. 9 for a gas powered gun according to the present invention, showing the position of the components when the bolt is in the rearward position.  
         [0043]    [0043]FIG. 11 is a top cross-sectional view of another preferred embodiment of a magazine assembly, with the operating rod deleted for clarity, illustrating the position of the components with the bolt in the forward position.  
         [0044]    [0044]FIG. 12 is a front cross-sectional view of a magazine assembly for a gas-powered gun according to the present invention.  
         [0045]    [0045]FIG. 13 is a top cross-sectional view of a magazine assembly of FIG. 1, showing the position of the components with the bolt in the rearward position.  
         [0046]    [0046]FIG. 14 is a top cross-sectional view of the magazine assembly of FIG. 11, showing the position of the components with the bolt in the forward position.  
         [0047]    [0047]FIG. 15 is a front cross-sectional view of an additional alternative embodiment of a magazine for a gas-powered gun of the present invention.  
         [0048]    [0048]FIG. 16 is a bottom view of an operating rod for a gas-powered gun according to the present invention.  
         [0049]    [0049]FIG. 17 is a side partially cut away view of a bolt, operating rod, and front portion of a bolt driver for a gas powered gun according to the present invention.  
         [0050]    [0050]FIG. 18 is a side view of a bolt and bolt driver for a gas powered gun according to the present invention.  
         [0051]    [0051]FIG. 19 is a side view of an air resistance bolt driver and floating mass bolt driver for a gas-powered gun according to the present invention.  
         [0052]    [0052]FIG. 20 is a side cut away view of a buffer assembly for a gas powered gun according to the present invention, showing the components configured for low recoil.  
         [0053]    [0053]FIG. 21 is a side cut away view of a buffer assembly for a gas-powered gun according to the present invention, showing the components configure for high recoil.  
         [0054]    [0054]FIG. 22 is a side cross-sectional view of a trigger assembly, valve assembly and bolt for a compressed gas gun of the present invention, showing an alternative preferred valve assembly.  
         [0055]    [0055]FIG. 23 is an exploded view of a captive assembly of a forward valve poppet, rear valve poppet, and spring for a gas powered gun according to the present invention. 
     
    
       [0056]    Like reference numbers denote like elements throughout the drawings.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0057]    The preferred embodiments of the present invention is a compressed gas powered gun that simulates the recoil of a conventional firearm discharging a powder propelled projectile. Referring to FIG. 1, a preferred embodiment of the compressed gas powered gun  10  is illustrated. The illustrated embodiments of the compressed gas powered gun simulates an AR-15 or M-16 rifle. The rifle  10  includes an action portion  12 , a barrel  14 , and a stock portion  16 . The stock portion  16  includes a shoulder stock  18  and a pistol grip  20 . The action portion  12  includes an upper receiver portion  22 , to which the barrel  14  is secured, and a lower receiver portion  24 , to which the shoulder stock  18  and pistol grip  20  are secured. A trigger  26  is located just ahead of the pistol grip  20  within the lower receiver portion  24 . The lower receiver portion  24  also includes at least one compressed gas container  28 , and may include a pressure gauge  30 . The upper receiver portion  22  includes a sight mounting rail  32  on its top surface, upon which the electronic dot sight  34  is illustrated. Any conventional sight may be substituted for the electronic dot sight  34 , including telescopic sights, or standard post front, aperture rear iron sights.  
         [0058]    Referring to FIGS.  2 - 8 ,  17 - 18 , and  22 , the trigger assembly  36 , bolts  38 , and valve assembly  40  are illustrated. The trigger  26  is pivotally secured within the lower receiver portion  24  at pivot  42 , and is biased towards its forward position by the trigger return spring  44 . The trigger  26  includes a finger-engaging portion  48 , and a selector-engaging portion  50 . The selector-engaging portion  50  is dimensioned and configured to abut a selector  46  when the trigger  26  is pulled rearward. The selector  46  is best illustrated in FIGS.  2 - 3 . The selector  46  includes an actuator  52  for permitting the shooter to rotate the selector  46  as explained below, and a trigger-engaging portion  54 . The trigger-engaging portion  54  includes a first surface  56 , corresponding to safe. A second surface  58  of the trigger-engaging portion  54  corresponds to semi-automatic fire. A third surface  60  of the trigger-engaging portion  54  corresponds to full automatic fire at a slow cyclic rate. This surface  60  is different from selectors used in firearms in that it is cut to a different geometry to be used as a cam stop for the trigger as opposed to a surface that controls disconnectors. It is therefore sufficiently different that it cannot be used in a firearm. Lastly, the trigger-engaging portion  54  defines a channel  62 , corresponding to full automatic fire at a high cyclic rate. Referring back to FIGS.  4 - 8 , the trigger  26  is pivotally secured to one end of a trigger bar  64 , with the other end of the trigger bar  64  secured to a sear trip  66 . The sear trip  66  includes a sear-engaging end  68 , having an upper radius surface  70  and a lower radius surface  72 . The sear  74  is pivotally secured within the lower housing  24  by the sliding pivot  76 . The sear  74  includes a front end  78 , dimensioned and configured to engage the sear trip  66 , and a back end  80 , dimensioned and configured to mate with a notch  82  defined within the bolt  38 . A spring  75  biases the sear rearward, and the front end  78  downward. The bolt  38  contains floating mass  39 , and includes a bolt key  83 , dimensioned and configured to secure an operating rod (described below). A spring-biased bolt driver is located directly behind the bolt  38 , as will also be explained below. The forward portion of the bolt preferably includes an O-ring  84  around its circumference.  
         [0059]    The valve assembly  40  includes a housing  86 , a forward valve  88 , a rear valve  90 , and a spring  92  between the forward valve  88  and rear valve  90 . The front valve  88  is stationary. The housing  86  reciprocates between a forward position and a rearward position, with the inward flange  94  bearing against the front O-ring  96  to close the front valve  88  when the housing  86  is in its rearward position, and with the forward position of the housing  86  corresponding to the front valve being opened. The rear valve  90  reciprocates within the housing  86 , with the rearward position of the valve  90  bringing the O-ring  98  against the housing&#39;s rear flange  100 , thereby closing the rear valve. When the rear valve  90  moves forward relative to the housing  86 , the rear valve  90  is opened. Compressed gas is supplied to the valve assembly  40  through the hose  102 , connected between the valve  40  and the compressed gas channels  104  within the lower receiver  24 . The compressed gas container  28  is secured to the compressed gas channels  104 , thereby supplying compressed gas through the channels  104 , hose  102  to the valve assembly  40 . The rear end of the housing  86  also includes an O-ring  106 .  
         [0060]    Referring to FIGS.  9 - 14  and  16 - 17 , a preferred embodiment of a magazine assembly  108  is illustrated. A preferred magazine is a cylinder  110 , located immediately in front of the valve assembly  40 , and directly behind the barrel  14 . A cylinder is defined herein as a rotary magazine similar to that used in a revolver wherein a plurality of firing chambers are arranged around the circumference, and is not necessarily a perfect geometrical cylinder. Cylinder  110  rotates about a central axis (not shown, and well known in the art) and has a plurality of chambers  112 , parallel to the central axis, and bored around the circumference. A preferred and suggested number of firing chambers  112  is six, although a different number may easily be used. The firing chambers  112  are each dimensioned and configured to receive one projectile, with the projectile positioned so that compressed air from the valve  88  will be positioned behind the projectile. The cylinder  110  also includes a plurality of flutes  114  around its circumference, with the flutes  114  located between the chambers  112 , and equal in number to the number of chambers  112 . A spring-biased bearing  116  preferably engages the flutes  114  to precisely align a chamber  112  of the cylinder  110  with the barrel  14 . The bearing  116  preferably has a radius larger than the radius of the flutes  114 , thereby facilitating more precise alignment.  
         [0061]    Indexing of the cylinder  110  is controlled by movement of the bolt  38 . The bolt key  83  secures an operating rod  118  to the bolt  30 , so that as the bolt  38  reciprocates, the operating rod  118  will reciprocate with the bolt  38 . The operating rod  118 , shown in phantom for maximum clarity, defines an angled slot  120  along its bottom surface. A pawl assembly  122  is located directly behind the cylinder  110 . The pawl assembly  122  includes a pawl carrier  124 , having a spring-biased pawl  126 . The pawl carrier  124  includes a pin  128 , dimensioned and configured to fit within the angled slot  120  of the operating rod  118 . The pawl  126  includes a reloading tab  130 , and a cylinder-engaging end  132  having a pusher surface  134  and ramp surface  136 . The cylinder-engaging end  132  is biased into one of chambers  112  by the spring  138 . The magazine assembly  108  may also include a magazine tube  140 , aligned with one of the chambers  112  of the cylinder  110 . The magazine tube  140  is dimensioned and configured to contain a plurality of spherical projectiles. The magazine tube  140  includes a spring-biased follower  142 , and has a loading gate  144  at its forward end. In one preferred embodiment, the chamber  112  in the three o&#39;clock position when viewed from the rear is aligned with the barrel  14 , and the chamber in the eleven o&#39;clock position when viewed from the rear is aligned with the magazine tube  140 . Additionally, in one preferred embodiment, the pawl  126  acts on the chambers in the eleven o&#39;clock and one o&#39;clock positions when viewed from the rear, as will be explained below.  
         [0062]    An alternative embodiment of a magazine assembly  108  is illustrated in FIG. 15. The cylinder  110  has been replaced by an elongated bar  146 , having a plurality of chambers  148 , indexing holes  150 , and flutes  152  along its bottom surface. At least one spring-biased bearing  116  engages a flute  152  to align the chambers  148  with the barrel  14 . A pair of slots  154 ,  154  permit the rod  146  to be inserted into the rifle  10  by accommodating the pawl  126 . As will be seen below, indexing of the magazine  146  is very similar to the indexing of the cylinder  110 .  
         [0063]    Referring to FIGS.  18 - 21 , the buffer system  158  is illustrated. A preferred buffer system  158  includes an air piston bolt driver  160 , a floating mass bolt driver  162  having a floating mass  164  therein, and a spring  166  disposed therebetween. The air piston bolt driver may preferably be made of two pieces, a forward portion  168  and rear portion  170 . The buffer system  158  is located directly behind the bolt  38 , and is housed within a buffer tube  172  within the shoulder stock  18 . Depending on the length of the buffer tube  172 , the forward portion  168  of the air resistance bolt driver may either be attached or removed from the rear portion  170  of the air piston bolt driver  158 .  
         [0064]    Referring to FIGS. 22 and 23, an improved valve assembly  174  is illustrated. As before, this valve includes a housing  176 , a forward valve  178 , a rear valve  180 , and a spring therebetween  182 . The valve assembly  174  is a captive assembly, permitting easy disassembly and reassembly. The front valve  178  and rear valve  180  include mating male and female components  184 ,  186  forming a telescoping spring guide. As before, moving the valve housing  176  forward with respect to the front valve  178  opens the front valve, and moving the rear valve  180  forward with respect to the housing  176  open the rear valve  180 . The spring  182  biases the rear valve  180  and housing  176  rearward, closing both valves.  
         [0065]    To use the rifle  10 , a gas cartridge  28  is first secured to the compressed gas channel  104 . At least one gas cartridge  28  must be used, and more than one may be used. If desired, a pressure gauge  30  may also be connected to the compressed gas channels  104 . The gas selected may be either compressed air, or any compressed gas commonly used for air guns. One example is carbon dioxide. Next, projectiles are loaded into the magazine. If a rotary magazine or cylinder  110  is used, any projectile suitable for use in an air gun may be used, including spherical projectiles, conventional pellets, darts, etc. The cylinder  110  is loaded by first depressing the bearing  116  so that it does not block removal of the cylinder  110 , and then pushing forward on the reloading tab  130 , thereby retracting the pawls end  132  from the chamber. The cylinder  110  is now free to exit the rifle  10 . The projectiles are pushed into place through the front portion of the chambers, and secured with friction. After loading all six chambers, the cylinder  110  may be inserted back into place within the rifle  10 , after which the shooter re-engages the bearing  116  with the magazine flute  114 . If a tubular magazine is used, preferred projectiles include spherical projectiles. These may be loaded by first retracting the follower  142  using a finger tab secured to the follower (not shown and well known in the art), opening the loading gate  144 , and pouring spherical projectiles into the magazine tube. Releasing the follower  102  will push the first spherical projectile into the chamber  112  aligned with the tubular magazine  140 .  
         [0066]    Compressed air will be supplied from the compressed air container  28 , through the compressed air channels  104  and hose  102  to the center portion of the valve assembly  40  between the forward valve  88  and rear valve  90 . Before firing, the trigger mechanism  36 , valve assembly  40  and bolt  38  are in the positions illustrated in FIG. 4. The bolts  38 , although biased forward by pressure from the spring  166 , is held in its rear position by the rear end  80  of the sear  74  engaging the notch  82 . Pressure from the spring  75  holds the sear  74  in this position, forward pressure from the bolt  38  against the sear  74  pushes the sear towards its forwardmost position on the sliding pivots  76 . The trigger spring  44  holds the trigger  26  in its forwardmost position. The selector  46  may be rotated to the appropriate position, corresponding to safe, semi-automatic, or full automatic at a low or high cyclic rate. FIG. 5 depicts the location of the parts when the trigger is pulled in semi-automatic mode. Trigger  26  has been pulled rearward until the selector-engaging portion  50  engages the surface  58  of the selector  46 . The trigger bar  64  moves rearward, thereby pivoting the end  68  of the sear&#39;s trip  66  upward so that the radiused surface  70  pushes the sear&#39;s forward end  78  upward, thereby pivoting the sear&#39;s back end  80  downward, releasing the bolt  38  to travel forward. During the forward travel of the bolt  38 , the operating rod  118  moves from the rearward position depicted in FIGS. 10 and 13 to the forward position depicted in FIGS. 9 and 14. The pawl carrier  124  is thereby moved from its right side position of FIGS. 10 and 13 to its left side position of FIGS. 9 and 14. The pawl&#39;s end  132  is pushed out of the chamber  112  in the one o&#39;clock position when viewed from the rear (FIGS. 10 and 13) to the eleven o&#39;clock position of FIGS. 9 and 14, without rotating the cylinder  110 . When the bolt  38  reaches its forwardmost position, air pressure between the bolt  38  and valve housing  86 , enhanced by the O-rings  84  and  106 , causes the valve housing  86  to move forward, thereby opening the forward valve  88 . This releases compressed air to a position immediately behind the projectile in the chamber  112  aligned with the barrel  14 , thereby discharging the projectile. At the same time, the bolt  38  strikes the rear valve  90 , thereby moving the rear valve  90  forward to open the rear valve  90 , thereby releasing compressed air to the bolt  38 . The bolt  38  is thereby pushed to its rearward position as the pressure from the compressed air overcomes the bias of the spring  166 . At the same time, the operating rod  118  is pulled from its forward position of FIGS. 9 and 14 to its rearward position of FIGS. 10 and 13. The pawl carrier  24  is thereby moved from its left most position to its right most position. As the pawl carrier  124  moves, the surface  134  of the pawl  126  engages the wall of a cylinder  112 , thereby pushing the cylinder  110  so that the next chamber  112  is aligned with the barrel  14 . The bearing  116  is briefly biased out of the flute  114 , engaging the next flute  114  once the appropriate  112  chamber is aligned with the barrel  14 . The above portion of the firing sequence, although based on semi-automatic fire, is identical for full automatic fire. The subsequent portion of the firing sequence changes depending on whether semi-automatic or full automatic fire is selected, and the rate of full automatic fire selected.  
         [0067]    [0067]FIG. 6 depicts the location of the components after firing a shot in semi-automatic mode, with the trigger still depressed. The spring  75  has pulled the sear  74  to the rear, where the end  78  slips off the radiused surface  70 , permitting the sear to rotate so that the rear end  80  rotates upward. The bolt  38  is retracted to a position slightly behind the point where the notch  82  engages the sear  74 . As the bolt  38  returns forward under pressure from spring  166 , the notch  82  and sear  74  engage each other, thereby arresting forward travel of the bolt  38 . At this point, releasing the trigger  26  is necessary to fire another shot.  
         [0068]    [0068]FIG. 7 depicts the position of the parts when the rifle  10  is discharged in full automatic mode at a slow rate of fire. In this mode of operation, the selector  46  is rotated so that the surface  60  engages the selector-engaging portion  50  of the trigger  26 . The trigger  26  is thereby permitted to move back farther than in semi-automatic mode. As before, gas pressure forces the bolt  38  back to a position slightly behind the point wherein it engages the sear  74 . The sear trip  66  is thereby rotated slightly higher, so that the lower radius  72  pushes upward on the front end  78  of the sear  74 . The sear is pulled towards its rear most position on the sliding pivot  76  by the spring  75 , and is thereby also pulled so that the rear end  80  of the sear  74  is rotated upward. As the bolt  38  returns forward under pressure from spring  166 , about {fraction (1/32)} nd  inch of the rear end  80  of the sear  74  catches the notch  82  of the bolt  38 . The floating mass  39 , which at this point will be located in the rear portion of the bolts  38 , has slowed the bolt  38  sufficiently so that it will momentarily catch on the sear  74 . When the bolt  38  engages the sear  74 , forward pressure applied to the sear  74  by the bolt  38  will cause the sear  74  to cam off the radiused surface  70  as it moves towards its forwardmost position on the sliding pivot  76 , rotating the sear  74  out of the path of the bolt  38 . The bolt  38  is then free to travel forward to discharge another shot.  
         [0069]    [0069]FIG. 8 depicts the location of the parts if full automatic fire is selected. The selector  46  is rotated so that the selector-engaging portion  50  of the trigger  26  corresponds to the channel  62  within the selector  46 , permitting the trigger  26  to travel to its maximum rearward position. The sear trip  66  is thereby rotated to its maximum upward position, thereby rotating the sear  74  completely out of the way of the bolt  38 . When the bolt  38  travels rearward sufficiently for the spring  166  to overcome the air pressure from the valve  90 , there is nothing to impede the forward motion of the bolt. This results in a maximum cyclic rate.  
         [0070]    A typical cyclic rate for full automatic fire with the low cyclic rate is approximately 600 rounds per minute. A typical cyclic rate for a full automatic fire at a high cyclic rate is approximately 900 rounds per minute, approximately simulating the cyclic rate of an M-16 rifle.  
         [0071]    Upon reading the above description, it becomes obvious that a magazine  146  may be substituted for the cylinder  110  without changing the basic operation of the rifle  10 . As the bolt  38  travels forward, the pawl carrier  124  will move from right to left as before, indexing the pawl  126  from one indexing chamber  150  to the next indexing chamber  150 . As the bolt  38  travels rearward, the pawl carrier  124  will move from left to right as before, causing the pawl  126  to index the magazine  146  so that the next firing chamber  148  is aligned with the barrel  14 . As before, the bearings  116  will fit within the corresponding flutes  152  to align the chambers  148  precisely with the barrel  14 .  
         [0072]    The airgun  10  has two accuracy-enhancing features. The combination of the bearing  116  and smaller radius flutes  114  ensures that the chamber  112  of the cylinder  110  aligns with the barrel  14  so precisely that a forcing cone at the breech end of the barrel is not required. This provides a totally straight path for the projectile throughout the chamber  112  and barrel  14 . Additionally, as compressed gas pressure from the container  28  decreases, the bolt  38  will push the valve  90  further inward as it strikes the valve  90 , thereby increasing the gas flow within the valve assembly  40 . This ensures that each projectile will have a substantially consistent velocity. Therefore, the projectile will have a substantially consistent energy and trajectory.  
         [0073]    While a specific embodiment of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalence thereof.