Abstract:
Methods, systems and devices for an adjustable gas block with variable gas port dimensions to control the amount of gas in the gas block before the gas enters into the gas tube. The adjustable gas block includes a gas block barrel bore to slide the block over a barrel and a gas tube bore to mate with the firearm gas tube, a gas port between the barrel bore and the gas tube bore, a sliding adjustment plate with different adjustment gas ports to slide one of the gas ports into alignment with the block gas port and the barrel gas port, and a spring to hold the sliding gas port in alignment with the barrel gas port. An alignment hole in the gas tube bore can align the block gas port with the barrel gas port.

Description:
This application claims the benefit of priority to U.S. Provisional Application No. 61/569,929 filed on Dec. 13, 2011. 
    
    
     FIELD OF THE INVENTION 
     The present invention related generally to firearms and, more particularly, to a device, system, and method for an adjustable gas block with variable gas port dimensions that replaces the conventional gas block to control the amount of gas in the gas block before the gas enters into the gas system of a gas operated firearm. 
     BACKGROUND AND PRIOR ART 
     AR-15 rifles and similarly styled firearms have become a best-selling category of sporting firearms. The main mechanism of operation for the rifle utilizes a gas tube which can be seen by prior art patent by Eugene Stoner U.S. Pat. No. 2,951,424. Which is referred to as the Stoner gas system hereinafter. The Stoner gas system routes gas from a port in the barrel directly to a chamber formed in the bolt carrier. The bolt acts as the piston and is sealed with gas rings. 
     As the bullet is accelerating rapidly down the bore, it passes the gas port and gas begins to flow into the gas block where it is directed toward the bolt carrier via the gas tube. The pressure is high in the barrel, usually 15,000 psi depending on barrel length until the bullet leaves the muzzle. Typically a firearm gas block is a solid piece of metal that goes over the gas port of a barrel to capture the propellant gas to direct that gas to a gas tube or piston. A problem can occur when the gas pressure is too high or too low. 
     The AR15/M16/AR10 is a gas operated firearm which uses some of the propellant gases in its normal operation and that gas is expelled through a gas port in the barrel and either goes through a gas tube which ultimately dumps the gas in a chamber known as the bolt carrier which is the Stoner gas system; or is used to propel a piston which pushes an op-rod that impacts the bolt carrier known as ‘piston’ operated firearm. 
     In either case, when a sound suppressor is used, it creates a great amount of backpressure which has the following adverse affects. 
     1. Increased fouling which in turn decreases the reliability 
     2. Increased cyclic rate of fire 
     3. With the increased rate of fire, it makes it difficult for operators to control the firearm since it is different from what they are used to. 
     4. Increased cyclic rate also increases parts wear 
     5. The backpressure leaks gas through the back of the receiver which ends up in the operator&#39;s eyes making it more difficult to focus on the target 
     To solve the problems with the prior art, the Govnah gas regulation system addresses the adverse effects. The Govnah regulated gas block is initially comprised of three different variants. The first variant (v 1 ) uses a sliding block that is configurable to allow the operator to choose from two different positions. One position for a suppressor attached to the barrel and the other position when a suppressor is not used. The second variant (v 2 ) also uses a sliding block but has a third, middle position to completely disable the gas system which then requires the user to manually cycle the action. The ‘no gas port’ position can be used to eliminate any fouling from entering the firearm via the gas tube when a 22LR conversion kit is used. The third position can also have a larger than normal port size to allow more gas into the system for adverse conditions. The third variant (v 3 ) uses a circular block for multiple positions of varying port dimensions, including no port, to allow the user to regulate the amount of gas entering the system to compensate for any changing variables that affect the cycling of the gas operated host firearm. 
     Known prior art patents include U.S. Pat. No. 7,856,917 issued to Noveske and U.S. Pat. No. 7,921,760 issued to Tankersley. Noveske discloses an adjustable gas block designed to interface with an autoloading firearms gas system and has three positions of adjustment that are selected if a silencer is in use, not in use, or if the user desires to stop the autoloading function of the firearm entirely. This design works by restricting the flow of gas from the gas port in the barrel and does not vent excess gas into the atmosphere around the gas block. 
     The above device uses a rotating drum with two openings in the drum and a gas port to control the amount of gas that enters into the gas tube which are all pre-determined by the factory. The Govnah uses a sliding or rotating block which can be swapped out by the end user to meet the user&#39;s requirements. While the Govnah uses standard military specification gas tubes, the Noveske device uses a proprietary straight gas tube and as a result is elevated higher. In result, the Noveske device will not fit under a rail system. While the Noveske device can by adjusted by hand, this is not ideal when it is hot. It requires a special tool or gloves to adjust safely when hot. The Govnah can be adjusted by any device that can push the adjustment plate, ideally a bullet. 
     There are applications and benefits for each of the two devices which include providing users with two (v 1 ), three (v 2 ) or multiple (v 3 ) positions for gas regulation on the AR15/M16/AR10 platform using unmodified standard gas tubes; they do not require special tools to adjust the position; they reduce logistic issues in regards to parts availability since they work with standard gas tubes; and they work with drop in ‘piston’ operated conversion kits that are on the market such as the Ares Defense GXR-35 and Osprey Defense OPS-416. Neither of which have a built in mechanisms to manually select the gas intake of the respective systems. 
     The Govnah regulated gas block (v 1  and v 2 ) is low profile which allows it to fit under a rail system and still be accessible for adjustment using the tip of a bullet or other small diameter object to select the gas setting. Since the Govnah regulated gas block fits under a rail system, the design itself is protected by the rail system to prevent any damage or inadvertent changing of the gas setting. The Govnah also uses a symmetrical moving block which controls the gas. Since it is symmetrical, it can be installed two different ways. This allows the user to decide which direction they prefer to have the adjustment plate set. 
     The Govnah (v 3 ) provides users with a regulated gas block that can quickly adjust to multiple known port diameters to change the amount of gas that is entering the host firearm&#39;s gas system without disassembly or special tools. This feature is useful when the user changes any variable that affects the functioning of the gas operated host firearm such as different buffers, sound suppressors, ammunition or springs. 
     The Govnah also incorporates an alignment hole for installation into the gas block body itself while prior art U.S. Pat. No. 7,921,760 accomplishes this with a separate installation device which requires dimpling the barrel to maintain alignment once the actual gas block is installed. The Govnah doesn&#39;t require dimpling since alignment is performed with the actual gas block body not a separate installation device. 
     What is needed to solve the problem with the prior art gas block is an adjustable gas port assembly that functions as a gas regulator for AR-15 rifles and similarly styled firearms. The present invention uses an adjustable gas block with variable gas port dimensions to control the amount of gas in the gas block before the gas enters into the gas tube or piston. 
     SUMMARY OF THE INVENTION 
     A primary objective of the present invention is to provide methods, systems and devices for an adjustable gas block with variable gas port dimensions that replaces the conventional gas block to control the amount of gas in the gas block before the gas enters into the gas tube of a gas operated firearm. 
     A secondary objective of the present invention is to provide methods, systems and devices for an adjustable gas block for the AR15/M16/AR10 family of firearms, but is not limited to only that family and can be used for virtually any firearm that is gas operated. 
     A third objective of the present invention is to provide methods, systems and devices for an adjustable gas block with a sliding adjustment plate with different adjustment plate gas ports to slide one of the different gas ports into alignment with the adjustable gas block gas port and the barrel gas port. 
     A fourth objective of the present invention is to provide methods, systems and devices for an adjustable gas block with an alignment hole in the gas tube bore can be used to align the adjustable gas block gas port with the barrel gas port. 
     A fifth objective of the present invention is to provide methods, systems and devices for an adjustable gas block which utilizes a standard un modified gas tube and barrel. 
     A sixth objective of the present invention is to provide methods, systems and devices for an adjustable gas block which requires no special tools to change the adjustment. Use the tip of a bullet or other small diameter object. 
     A seventh objective of the present invention is to provide methods, systems and devices for an adjustable gas block which can fit under a rail system and can still be adjusted with no special tools 
     An eighth objective of the present invention is to provide methods, systems and devices to extend the service life of a barrel when the gas port has been eroded. 
     A ninth objective of the present invention is to provide methods, systems and devices that gives the operator the option to allow excess gas into the firearm for adverse conditions. 
     A tenth objective of the present invention is to provide methods, systems and devices that have a modular regulation mechanism in this case the regulator plate. The regulator plate can be swapped out by the end user for varying conditions or for replacement due to wear. 
     A first preferred embodiment provides adjustable gas block assembly that includes an adjustable gas block having a gas block barrel bore to slide the adjustable gas block over a barrel of a firearm and a gas tube bore to mate with the gas tube of the firearm. The adjustable gas block includes a gas port in the adjustable gas block between the barrel bore and the gas tube bore, a sliding adjustment plate having two or more different adjustment plate gas ports movably positioned between the adjustable gas block barrel bore and the gas tube bore in the gas block to slide one of the two or more different adjustment plate gas ports into alignment with a gas port between the barrel bore and the gas tube bore and the barrel gas port, a spring assembly to hold a selected one of the two or more different adjustment plate gas ports in the sliding adjustment plate in alignment with a barrel gas port, and set screws for attaching the adjustable gas block to the barrel of the firearm. 
     The adjustable gas block can include an alignment hole in the top of the gas tube bore in alignment with the gas port in the adjustable gas block and the barrel gas port. 
     The sliding adjustment plate includes a first adjustment plate gas port and a second adjustment plate gas port that is larger in diameter than the first adjustment plate gas port and can alternatively include a third adjustment plate gas port that is larger in diameter (or no port) than the second adjustment plate gas port. The sliding adjustment plate can include one or more adjustment plate baffles in a top side of the sliding adjustment plate to capture a gas escaping from the space between the adjustment gas plate and the gas tube bore. The adjustable gas block can include adjustable gas block baffles parallel to the one or more adjustment plate baffles in the adjustable gas block below the sliding adjustment plate. The spring assembly includes detent dimples in one side of the sliding adjustment plate each aligned with one of the two or more adjustment plate gas ports, a detent pin to mate with the adjustment plate detent dimples and a detent pin spring to releasably secure the detent pin in the adjustment plate detent dimple until a force is applied to move the sliding adjustment plate between two or more positions. 
     A second preferred embodiment provides a method to control the amount of gas in the gas block before the gas enters into a gas tube or piston that includes removing a prior art gas block from a firearm that uses gas operation, sliding an adjustable gas block with a barrel bore and a gas tube bore onto a barrel of the firearm, securing the adjustable gas block with two or more set screws in the base of the adjustable gas block, and sliding an adjustment plate to align one of two or more different diameter gas ports with a gas tube port. 
     A third embodiment provides an adjustable gas block that includes a body with a gas block barrel bore to slide the adjustable gas block over a barrel of a firearm and a gas tube bore to mate with the gas tube of the firearm, a gas port in the adjustable gas block between the barrel bore and the gas tube bore, a sliding adjustment plate with two or more different diameter gas ports movably positioned to slide one of the two or more different adjustment plate gas ports into alignment with the adjustable gas block gas port and the barrel gas port, and a spring assembly to hold a selected one of the different adjustment plate gas ports in alignment with a barrel gas port, threaded holes in a bottom of the adjustable gas block to accept set screws to attach the adjustable gas block to the barrel of the firearm. 
     Further objects and advantages of this invention will be apparent from the following detailed description of preferred embodiments which are illustrated schematically in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a top perspective view of rifle with prior art gas block installation. 
         FIG. 2  shows a section detail of prior art gas block installation of  FIG. 1 . 
         FIG. 3  is a top perspective view of a rifle with new adjustable gas block installation according to the present invention. 
         FIG. 4  is a section detail of new adjustable gas block installation of  FIG. 3 . 
         FIG. 5  is a side view of a prior art gas block of  FIG. 1 . 
         FIG. 6  is a rear view of the prior art gas block of  FIG. 1 . 
         FIG. 7  is a bottom view of the prior art gas block of  FIG. 1 . 
         FIG. 8  is a right perspective view of the prior art gas block of  FIG. 1 . 
         FIG. 9  is a left perspective view of the prior art gas block of  FIG. 1 . 
         FIG. 10  is a side view of an adjustable gas block shown in  FIG. 3 . 
         FIG. 11  is a front view of the adjustable gas block shown in  FIG. 3 . 
         FIG. 12  is a rear view of the adjustable gas block shown in  FIG. 3 . 
         FIG. 13  is a top view of the adjustable gas block shown in  FIG. 3 . 
         FIG. 14  is a bottom view of the adjustable gas block shown in  FIG. 3 . 
         FIG. 15  is a left perspective view of the adjustable gas block shown in  FIG. 3 . 
         FIG. 16  is a right perspective view with section lines (also see  FIGS. 19-22  &amp;  31 - 35 ). 
         FIG. 17  is a top exploded perspective view of a 2 position embodiment. 
         FIG. 18  is a bottom exploded perspective view of the 2 position embodiment. 
         FIG. 19  is a top sectioned perspective showing 2 position adjustment plate lifted to expose the gas port. 
         FIG. 20  is a sectioned perspective showing small hole in adjustment plate aligning with gas block gas port. Detent pin is shown seated into an adjacent detent dimple. 
         FIG. 21  is a sectioned perspective showing adjustment plate in transition between its two positions. Detent pin showing sliding on surface between the detent dimples. 
         FIG. 22  is a left sectioned perspective showing large hole in adjustment plate aligning with gas block gas port. Detent pin is shown seated into adjacent detent dimple. 
         FIG. 23  is a top view of the 2 position adjustment plate. 
         FIG. 24  is a front view of the 2 position adjustment plate. 
         FIG. 25  is a rear view of the 2 position adjustment plate. 
         FIG. 26  is a side view of the 2 position adjustment plate. 
         FIG. 27  is a bottom perspective view of the 2 position adjustment plate. 
         FIG. 28  is a top perspective view of the 2 position adjustment plate. 
         FIG. 29  is a top exploded perspective view of 3 position embodiment. 
         FIG. 30  is a bottom exploded perspective view. 
         FIG. 31  is a top sectioned perspective showing 3 positions adjustable plate lifted to expose gas port. 
         FIG. 32  is a sectioned perspective showing small-sized hole aligned with gas block gas port. Detent pin is shown seated in adjacent detent dimple. 
         FIG. 33  is a sectioned perspective showing adjustment plate in transition between positions. Detent pin showing sliding on surface between the detent dimples. 
         FIG. 34  is a sectioned perspective showing large hole aligned with gas block gas port. Detent pin is shown seated in adjacent detent dimple. 
         FIG. 35  is a sectioned perspective showing mid hole aligned with gas block gas port. Detent pin is shown seated in adjacent detent dimple. 
         FIG. 36  is a top view of 3 position adjustment plate. 
         FIG. 37  is a rear view of 3 position adjustment plate. 
         FIG. 38  is a front view of 3 position adjustment plate. 
         FIG. 39  is a side view of 3 position adjustment plate. 
         FIG. 40  is a bottom perspective of 3 position adjustment plate. 
         FIG. 41  is a top perspective of 3 position adjustment plate. 
         FIG. 42  is a section detail of new adjustable gas block installation onto rifle barrel. Block ready to slide onto barrel 
         FIG. 43  shows the block slid over barrel ready to align block gas port to barrel port. Alignment pin positioned for alignment. Set screws in gas block shown backed off. 
         FIG. 44  shows the alignment pin shown penetrating block and barrel establishing alignment of gas ports. Set screws in gas block shown tightened. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before explaining the disclosed embodiments of the present invention in detail it is to be understood that the invention is not limited in its application to the details of the particular arrangements shown since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation. 
     The following is a list of reference numerals used in the description and the drawings to identify components:
       10  Rifle (Prior Art)     20  Rifle barrel (Prior Art)     30  Gas tube (Prior Art)     40  Bullet (Prior Art)     50  Gas Block (Prior Art)     60  Gas port in barrel (Prior Art)     70  Gas port in block (Prior Art)     80  Gas tube bore in block (Prior Art)     90  Gas port in gas tube (Prior Art)     100  Set screws secure block to barrel     110  New adjustable gas port assembly     120  Sliding adjustment plate (2 position)     130  Detent pin     140  Detent pin spring     150  Adjustment plate gas port     160  Adjustable gas block     170  Gas block barrel bore (Prior Art)     180  Adjustable gas block barrel bore     190  Sliding adjustment plate (3 position)     200  Adjustment block alignment hole     210  Gas trap baffles on adjustment plate     220  Detent dimples     230  Gas trap baffles on gas block     240  Gas port in adjustment gas block     250  New adjustable gas port assembly (3 positions)     270  Rifle bore     280  Alignment pin     290  Bullet fired from rifle pressurizes bore     300  Pressure travels through gas port and gas tube to operate gas actuated rifle mechanisms.   

       FIG. 1  is a top perspective view of rifle  10  with prior art gas block installation showing the rifle barrel  20 , the gas tube  30  and gas block  50 .  FIG. 2  shows a section detail of prior art gas block installation showing the barrel  20 , the rifle bore and a bullet  40  fired from the rifle pressurized bore  290 . Also shown is the prior art gas block  50  and the gas block barrel bore  170  that is secured to the barrel with set screws  100 . 
     The main mechanism of operation for the rifle is the Stoner gas system. Gas in the barrel  20  is trapped as the bullet  40  moves past a gas port  70  located above the rifle&#39;s front sight base. As shown, the gas port includes the gas port in the barrel  60 , the gas port in the block  70  and the gas port in the gas tube. The gas rushes into the gas ports in the barrel and the block  60  and  70 , through the gas port  90  and down the gas tube  30 . Here, the gas tube  30  protrudes into a “gas key” (not shown) which accepts the gas and funnels it into the bolt carrier. The bolt unlocks when enough gas pressure is generated. 
       FIG. 3  is a top perspective view of a rifle  10  with an adjustable gas block  110  installation according to the present invention.  FIG. 4  is a section detail of new adjustable gas block assembly  110  installed on a rifle. The adjustable gas block  160  is installed by sliding the adjustable gas block onto the barrel and attaching the adjustable gas block to the rifle barrel  20  with set screws  100 . As shown, the assembly includes a gas block barrel bore  180 , a gas tube bore  80  in the gas block  160  and a sliding adjustment plate  150  between the barrel bore and gas tube bore. The gas port  70  in the adjustable gas block  160  is aligned with the barrel gas port  60 , both of which are aligned to feed into the gas tube gas port  90 . 
     Referring back to the prior art gas block installation shown in  FIG. 1 , details of the gas block are show in  FIG. 5-9  which show a side view, rear view, bottom view, right perspective view and left perspective view, respectively, of the prior art gas block. The right view in  FIG. 8  shows gas block barrel bore  170 . Rear view shown in  FIG. 6  shows both the gas block barrel bore and the gas tube bore  80 . The bottom view of  FIG. 7  shows the set screws  100  that secure the gas block  50  to the rifle barrel  20 . Looking into the gas block barrel bore  170  in  FIG. 9  shows the gas tube bore  70  in the gas block. 
     In contrast,  FIGS. 10-14  show details of the adjustable gas block according to the present invention.  FIGS. 10 and 13  show adjustable gas block assembly  110  showing the sliding adjustment plate  120  and detent pin spring  140  in the adjustable gas block  160 . The front view of the adjustable gas block shown in  FIG. 11  shows the positional sliding adjustment plate  120  and the detent spring in relation to the barrel bore  180  while the back view shown in  FIG. 12  shows the relational position with the gas tube bore  80  in the adjustable gas block  160 . Similar to the prior art, the adjustable gas block is attached to the barrel with set screws  100  as shown in  FIG. 14 . 
       FIGS. 15 and 16  are left and right perspective views, respectively, of the adjustable gas port assembly  110  showing the adjustable gas block  160 , the sliding adjustment plate  120 , the adjustment block alignment hole  200 , and the adjustment gas block barrel bore  180 . Unlike the prior art gas blocks, in a preferred embodiment of the present invention the adjustable gas block  160  includes adjustment block alignment hole  200  in the gas tube. With the prior art gas blocks, it is common for the gas block to be mis-aligned with the barrel&#39;s gas port. Some users don&#39;t realize that you can install a gas tube after installing the gas block. 
     After the adjustable gas block  160  is mounted on the barrel  20  without the gas tube  30  installed, prior to tightening the set screws  100 , the user inserts a drill rod or gauge pin into the alignment hole  200  to make sure the drill rod or gauge pin goes all the way into the barrel&#39;s gas port  60  to ensure that there is no alignment issue. After confirming alignment, the set screws are tightened and the gas tube  30  is installed by inserting the gas tube into the upper receiver upside down, rotating the gas tube 180 degrees then inserting the gas tube into the adjustable gas block  160  and inserting the gas tube roll pin.  FIG. 16  also includes section lines relating to  FIGS. 19-22  and  31 - 35 . 
     Another novel feature is the location of the mounting set screws  100  that secure the adjustable gas block  160  to the rifle barrel  20 . The mounting set screws  100  are shifted approximately one-half inch forward toward the muzzle to avoid misalignment of the gas port  60  in the barrel. The placement of the set screw addresses a common problem associated with the prior art replacement gas ports that have the same set screw locations. For example, alignment of the Govnah regulator is critical to proper operation. To prevent mis-alignment, the mounting location of the set screws in the present invention have been moved so the set screws are not inserted into any pre-existing grooves on a barrel, if any are present. 
       FIGS. 17 and 18  are top and bottom, respectively, exploded perspective views of a 2 position embodiment of the present invention showing the sliding adjustment plate  120  with two different size adjustment plate gas ports  150  and the adjustable gas block alignment hole  200 . The sliding adjustment plate  120  is firmly held in place by the detent pin  130  and detent pin spring  140 . The sliding adjustment plate  120  has two detent dimples configured to mate with the rounded end of the detent pin. The detent spring  140  applies sufficient force to hold the sliding adjustment plate  120  in place when the pin  130  is in the sliding adjustment plate dimple  220 . Since the sliding plate dimples  220  are rounded, when the user applies a force to change the position of the sliding adjustment plate  150 , the detent pin  130  is dislodged to allow the sliding adjustment plate  120  to move. The sliding adjustment plate  120  moves until the detent pin  130  is seated in the other sliding adjustment plate dimple  220  aligning the other adjustment plate gas port  150  with the gas port  240  in the gas block and the barrel gas port. 
     Details of the sliding adjustment plate  120  are shown in  FIGS. 19 and 20  which show a top sectioned perspective showing the 2 position adjustment plate  120  lifted to expose gas port  240  in the gas block  160  and a sectioned perspective showing the small gas port in adjustment plate aligned (dashed line) with the gas block gas port  240 . The detent pin  130  is shown seated in an adjacent detent dimple  220 . The detent pin  130  is located in a trough in the adjustable gas block  160  parallel with the barrel of the firearm and the detent pin is configured to hold the detent pin  130  securely in the trough to prevent the detent pin  130  from moving sideways when the sliding adjustment plate  120  slides between the two different gas port  150  positions. The detent pin  130  has a notch cut into it so that the detent spring  140  can pull the detent pin back so the regulator can be removed without tools. The detent spring  140  can also be used to aid in removing the detent pin  130  from the gas block body. 
       FIG. 20  shows the sliding adjustment plate  120  in a first position and extending outwardly from the left side of the gas block  160 ,  FIG. 21  shows the sliding adjustment plate  120  between the two different adjustment plate gas ports  150 , and  FIG. 22  shows the sliding adjustment plate  120  in the second position and extending outwardly from the right side of the gas block  160 . As shown, the sliding adjustment plate  120  has right and left sides that extend rearwardly as stops to prevent the sliding adjustment plate  120  from being unintentionally removed from the adjustable gas block  160 . 
     Another feature of the adjustable gas block of the present invention are the gas trap baffles  230  on the adjustable gas block  160  shown in  FIG. 19  and the gas trap baffles  210  shown in  FIG. 20  on the sliding adjustment plate  120 .  FIGS. 23-28  show 6 different views of the sliding adjustment plate  120 . Due to the nature of the design, there can be some clearance between the regulator and the adjustable gas block  160 . Some gas does leak out of this clearance although amount of leakage is marginal; the design reduces that leakage or delays it as much as possible. 
     The sliding regulator plate  120  has grooves as gas trap baffles  210  cut along each side of the gas ports  150  and between the two gas ports. As gas passes over the gas trap baffles  210 , turbulence is created which creates a gas trap between the adjustable gas block  50  and the top of the sliding adjustment plate  120 . Likewise, gas trap baffles  230  are cut into the top of the adjustable gas block  160  at the entrance of each side of the regulator openings. This creates a gas trap between the gas block  160  and the bottom of the sliding adjustment plate  120 . In another embodiment, a small hole can be machined at an angle at the bottom of the plate which would serve to jet gas into the gas trap baffles on the adjustable gas block. 
       FIG. 23  is a top view of the 2 position adjustment plate showing the two different gas ports  150 , three parallel gas trap baffles  210 , the two detent dimples  220  and the extended sides that act as a stop to prevent the adjustment plate  120  from being unintentionally removed.  FIG. 23  also shows the alignment of each adjustment gas port  150  with the detent dimples  220 .  FIG. 24  is a front view of the 2 position adjustment plate  120  and  FIG. 25  is a rear view of the 2 position adjustment plate  120  showing that the adjustment plate gas baffles  210  extending the length of the sliding adjustment plate  120  with the two detent dimples  220  located between the gas trap baffles  210 .  FIG. 26  is a side view of the 2 position sliding adjustment plate and  FIGS. 27 and 28  are bottom and top perspective views, respectively, of the 2 position sliding adjustment plate  120 . 
     A second embodiment provides a 3 position sliding adjustment plate  190 .  FIGS. 29 and 30  are top and bottom, respectively, exploded perspective views of the three position embodiment.  FIG. 31  is a top sectioned perspective view showing the 3 position sliding adjustment plate  190  lifted to expose gas port  240  in the adjustable gas block  160 .  FIGS. 36-41  show different views of the 3 position sliding adjustment plate  190 .  FIG. 36  is a top view of the 3 position sliding adjustment plate  190  and  FIGS. 37 and 38  are rear and front, respectively, views of the 3 position sliding adjustment plate  190 . As shown, the sliding adjustment plate  190  can have three gas ports  150  each of a different diameter, although the sliding adjustment plate can include a different number of gas ports such as the two gas port example previously shown and described or a three position adjustment plate with two gas ports separated by a position without a gas port, effectively blocking the gas in the barrel from escaping into the gas tube. 
     The 3 position sliding adjustment plate  190  also includes a fourth gas trap baffle  210  to capture any gas escaping from between the sliding adjustment plate  190  and the top of the adjustable gas block  160 . The detent pin  130  and spring  140  are the same configuration and serve the same function as described for the 2 position embodiment. 
       FIG. 32  is a sectioned perspective view showing a small-sized adjustment plate gas port  150  aligned with gas block gas port  240  with the detent pin  130  shown seated in detent dimple  220  aligned with the small sized adjustment plate gas port  150 . In  FIG. 33  the sliding adjustment plate  190  is shown in transition between positions as the detent pin  130  slides on the surface between two adjacent detent dimples  220 . As the user continues to apply pressure to move the sliding adjustment plate  190 , the detent pin  130  is seated in the next adjacent detent dimple  220  with the larger of the three gas ports  150  aligned with the gas port  240  in the adjustable gas block  160  as shown in  FIG. 34 .  FIG. 35  is a sectioned perspective showing mid hole aligned with gas block gas port. Detent pin  130  is shown seated in adjacent detent dimple  220 . 
     While the three gas ports are shown and described with a larger one of the gas ports in the center, the configuration is for example only and those skilled in the art will understand that the different diameter gas ports could be configured, for example, with the smallest gas port in the center position. Alternatively, the center position could not include a gas port, effectively blocking the gas discharge from the barrel from escaping into the gas tube via the adjustable gas block. 
       FIG. 42  is a section detail of new adjustable gas block assembly  110 / 240  installation onto rifle barrel  20  with the adjustable gas block  160  ready to slide onto barrel  20  in the direction shown by the arrows.  FIG. 43  shows the adjustable gas block  160  slid over barrel  20  ready to align the block gas port  240  to the gas port  60  in the barrel with an alignment pin  280  positioned for alignment. The set screws in gas block are shown backed off so that the adjustable gas block  160  can be rotated and moved to align the two gas ports.  FIG. 44  shows the alignment pin  280  penetrating the adjustable gas block  160  and barrel  20  establishing alignment of gas ports. With the gas ports aligned, the set screws in gas block are tightened as shown in  FIG. 44 . 
     In an alternative embodiment, the sliding adjustment plate is replaced with a dial. The dial uses a rotating adjustment disc in place of the sliding adjustment plate. The rotary adjustment plate is applicable for testing or use when conditions vary in terms of ammunition, springs and buffers and each can require a different diameter gas port. V 1 /V 2  options have fewer settings since increasing the number of settings adds complexity to a law enforcement officer or soldier. Military users typically have standard issue ammunition, springs and buffers so the rotary dial adjustment disc is not the ideal solution. Law enforcement is typically along those lines, but may not be as strict. 
     While the invention has been described, disclosed, illustrated and shown in various terms of certain embodiments or modifications which it has presumed in practice, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved especially as they fall within the breadth and scope of the claims here appended.