Patent Publication Number: US-8528458-B2

Title: Pressure-regulating gas block

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present patent application is a continuation-in-part patent application and claims priority from U.S. Provisional Patent Application Ser. No. 61/147,702, filed Jan. 27, 2009, entitled “Pressure-Regulating Gas Block,” and to PCT Patent Application No. PCT/US2010/022293, filed Jan. 27, 2010, entitled “Pressure-Regulated Gas Block,” both invented by Bernard T. Windauer, and the disclosures of both being incorporated by reference herein. 
     BACKGROUND 
     Military and tactical operations require various ammunition types and various types of semi-automatic and fully automatic firearms. The firearms are also used in both normal and silenced modes of operation. The various types of ammunition develop a wide range of gas pressures when the gunpowder burns. When silencers (sound suppressors) are used, they create a back pressure within the operating system of the firearm. The ambient temperatures in which the firearms are used also create a variation in the pressures within the firearm as the firearm is operated. Given all the conditions that cause variations in the pressures within the firearm, there are a seemingly infinite number of pressure variations that can occur. When a firearm is designed, the average working conditions are determined in view of expected variations in pressure within the firearm and stresses and construction material strengths calculated. 
     When a firearm is used in a semi-automatic mode without a silencer or in an automatic mode without a silencer, the speed of operation (cyclic rate) of the firearm is not a factor considered to affect a soldier&#39;s safety although the sound signature is considered to be a significant factor that adversely affect a soldier&#39;s safety due to alerting the enemy to the soldier&#39;s position. When a firearm is are used in the semi-automatic mode with a silencer, the cyclic rate of the firearm operation is not considered to be a significant factor that adversely affects the soldier&#39;s safety because the firearm only fires once per trigger squeeze, however, the sound signature could be a critical (i.e., life and death) factor depending on the ambient conditions. When a firearm is used in the fully-automatic mode with a silencer, the cyclic rate of the firearm operation and the sound signature could be a critical (i.e., life and death) factor to the soldier&#39;s safety depending on ambient conditions. A problem that has existed since the advent of gas-operated firearms that are used with silencers has been the increase in cyclic rate due to the increased backpressure created by the silencer installed on the end of the barrel. The cyclic rate increase due to the additional back pressure adds additional stresses to the firearm beyond the designed average working conditions causing material failures and ammunition-loading failures as well as an increased sound signature, both of which may compromise the safety of a soldier using the firearm. 
     Another problem that exists is the increase in cyclic rate of the firearm used in the semi-automatic and fully-automatic modes, which occurs when the ammunition type changes for a given firearm. Different ammunition types develop different operating pressures. Firearm operating temperatures based on duration of operation and ambient temperatures also affect operating temperatures. A difference in operating pressure above the pressure for which the firearm was designed increases in cyclic rate of the firearm, which causes excessive stresses on the operating parts of the firearm, and may cause breakage of the operating parts and/or ammunition-loading failures. The problems caused by greater-than-design pressures and/or increase in cyclic rate and sound signature (when used with a silencer) can result in creating a life and death situation for a soldier and/or the soldier&#39;s team members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject matter disclosed herein is illustrated by way of example and not by limitation in the accompanying figures in which like reference numerals indicate similar elements and in which: 
         FIG. 1A  depicts a cross-sectional view of a first exemplary embodiment of a Pressure-Regulating Firearm Gas Block (PRFGB) and a firearm through the barrel of the firearm along a longitudinal axis with a bullet approaching a first gas port; 
         FIG. 1B  depicts a cross-sectional view of the first exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet passing the first gas port; 
         FIG. 1C  depicts a cross-sectional view of the first exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet exiting the barrel and a flash arrestor/suppressor adapter; 
         FIG. 2A  depicts a second exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with a bullet approaching a first gas port; 
         FIG. 2B  depicts the second exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet having passed the first gas port and blocking a second gas port as the bullet travels toward the firearm flash arrestor/suppressor adapter; 
         FIG. 2C  depicts the second exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet exiting the barrel and flash arrestor/suppressor adapter; 
         FIG. 3A  depicts a third exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with a bullet approaching a first gas port; 
         FIG. 3B  depicts the third exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet having passed the first gas port and blocking a second gas port as the bullet travels toward the firearm flash arrestor/suppressor adapter; 
         FIG. 3C  depicts the third exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet exiting the barrel and flash arrestor/suppressor adapter; 
         FIG. 4A  depicts a fourth exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with a bullet  404  approaching a gas port; 
         FIG. 4B  depicts the fourth exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet having passed a gas port as the bullet travels toward the firearm flash arrestor/suppressor adapter; 
         FIG. 4C  depicts the fourth exemplary embodiment of a PRFGB and a firearm through the barrel of the firearm along a longitudinal axis with the bullet exiting the barrel and flash arrestor/suppressor adapter; and 
         FIG. 5  depicts a cross-sectional side view of a fifth exemplary embodiment of a PRFGB, a firearm through the barrel of the firearm along a longitudinal axis, and a suppressor according to the subject matter disclosed herein. 
     
    
    
     DETAILED DESCRIPTION 
     It should be understood that the word “exemplary,” as used herein, means “serving as an example, instance, or illustration.” Any embodiment described herein as “exemplary” is not to be construed as necessarily preferred or advantageous over other embodiments. 
       FIGS. 1A-1C  respectively show different time periods of operation for a first exemplary embodiment (timing/piston movement) of a Pressure-Regulating Firearm Gas Block (PRFGB)  100  mounted on a “select fire” (i.e., selectably semi-automatic or fully-automatic) firearm  150  according to the subject matter disclosed herein. In particular,  FIG. 1A  depicts a cross-sectional view of a first exemplary embodiment of the Pressure-Regulating Firearm Gas Block (PRFGB)  100  and a firearm  150  through the barrel  101  of firearm  150  along a longitudinal axis  151  with a bullet  104  approaching a first gas port  106 .  FIG. 1B  depicts a cross-sectional view of the first exemplary embodiment of PRFGB  100  and firearm  150  through barrel  101  of firearm  150  along longitudinal axis  151  with a bullet  104  passing first gas port  106 .  FIG. 1C  depicts a cross-sectional view of the first exemplary embodiment of PRFGB  100  and firearm  150  through barrel  101  of firearm  150  along longitudinal axis  151  with a bullet  104  exiting barrel  101  and a flash arrestor/suppressor adapter  114 . It should be understood that only a portion of firearm  150  is depicted in  FIGS. 1A-1C . It should also be understood that in one exemplary embodiment, firearm  150  comprises a semi-automatic firearm, a fully automatic firearm, or a combination thereof. Additionally, it should be understood that while PRFGB  100  is depicted as being remote from the mechanical loading and ejection components of firearm  150  (i.e., forward mounted on the barrel of firearm  150 ), PRFGB  100  could be positioned to be adjacent to (i.e., in relatively close proximity) the mechanical loading and ejection components of firearm  150 , or integrally (i.e., within the firearm receiver) to the mechanical loading and ejection components of the firearm. 
     The first exemplary embodiment of PRFGB  100  depicted in  FIGS. 1A-1C  is timing based and venting can be directly into the bore of the barrel of the firearm or directly into atmosphere through one or more side-located (not shown), top-located (not shown), or front located (not shown) relief ports according to the subject matter disclosed herein. As depicted in  FIGS. 1A-1C , PRFGB  100  comprises a housing  105 , an operating piston  103 , and a gas shut-off valve  107 . Housing  105  forms a gas cylinder  108 , which is a pressure chamber that is fluidly coupled to the bore  101   a  of barrel  101  through gas port  106  and gas shut-off valve  107 . During operation of firearm  150 , a bullet  104  is pushed down the bore  101   a  of a barrel  101  of firearm  150  by expanding high-pressure gas created from the burning of the gunpowder ( FIG. 1A ). 
     When bullet  104  passes a first gas port  106  ( FIG. 1B ), a portion of the high-pressure gas passes through gas port  106 , through the gas shut-off value  107  and enters gas cylinder  108 . The expanding gas pushes operating piston  103  rearward (to the right in  FIGS. 1A-1C ) to cycle a firearm operating rod  102  or directly operate the firearm cartridge loading and ejecting mechanical components (bolt/bolt carrier)(not shown) if the piston assembly is located in the receiver of the firearm (not shown). The increasing pressure formed by the expanding gas moves operating piston  103  rearward a certain distance, at which time the pressure reaches a designed pressure peak and the high-pressure gasses are then allowed to enter a relief port  109  and exit housing  105  either into the bore  101   a  of barrel  101 , which is depicted in  FIGS. 1A-1C , or to the atmosphere through side-, top-, or front-located relief ports in PRFGB housing  105 , which are not depicted in  FIGS. 1A-1C . Relief port  109  is fluidly coupled between cylinder  108  and the bore  101   a  of barrel  101 . Once the interior pressure within gas cylinder  108  has been vented, no additional force is pushing operating piston  103  and operating rod  102  rearward to cycle firearm  150 . 
     Once the rearward movement of the operating rod  102  reaches its physically limited movement ( FIG. 1C ), a recoil spring (not shown) moves operating rod  102  and operating piston  103  forward into their physically limited position in preparation for the next operating cycle. 
     The specific location of relief port  109  is dependent on design parameters for operator safety based on a visual signature (i.e., flame release) and/or a sound signature (i.e., pop sound of released high-pressure gas) during operation. In a situation in which venting high-pressure gas directly to the exterior of the firearm is not a life-and/or-safety compromising issue, relief portion  109  could be located in one exemplary embodiment on either side, front, or on the top of PRFGB housing  105 . In a situation in which venting high-pressure gas directly to the exterior of the firearm is a life-and/or-safety compromising issue, relief port  109  could be located in one exemplary embodiment on the bottom of PRFGB housing  105  (as depicted in  FIGS. 1A-1C ) to vent directly into the bore  101   a  of barrel  101  of firearm  150 . By design, the relative speed of the bullet compared to the speed of the gas and operating parts of PRFGB  100  eliminate the possibility of gas flowing backwards through relief port  109  into PRFGB  100 . In a situation in which venting high-pressure gas directly to the exterior of the firearm is a life-and/or-safety compromising issue, relief port  109  could be located in one exemplary embodiment on the front of PRFGB housing  105  (as depicted in  FIGS. 4A-4C ) to vent directly into the rear of a silencer (not shown) mounted on the barrel  101  of firearm  150 . 
       FIGS. 2A-2C  respectively show different time periods of operation of a second exemplary embodiment of the Pressure-Regulating Firearm Gas Block (PRFGB) mounted on a “select fire” (i.e., selectably semi-automatic or fully-automatic) firearm according to the subject matter disclosed herein. More specifically,  FIG. 2A  depicts a second exemplary embodiment of a PRFGB  200  and a firearm  250  through the barrel  201  along a longitudinal axis  251  of the firearm with a bullet  104  approaching a first gas port  206 .  FIG. 2B  depicts the second exemplary embodiment of PRFGB  200  and a firearm  250  through the barrel  201  of the firearm along a longitudinal axis  251  with bullet  204  having passed first gas port  206  and blocking a second gas port  210  as bullet  204  travels toward the firearm flash arrestor/suppressor adapter  214   FIG. 2C  depicts the second exemplary embodiment of PRFGB  200  and a firearm  250  through the barrel  201  of firearm  250  along longitudinal axis  251  with bullet  204  exiting the barrel  201  and flash arrestor/suppressor adapter  214 . It should be understood that only a portion of firearm  250  is depicted in  FIGS. 2A-2C . It should also be understood that in one exemplary embodiment, firearm  250  comprises a semi-automatic firearm, a fully automatic firearm, or a combination thereof. Additionally, it should be understood that while PRFGB  200  is depicted as being remote from the mechanical loading and ejection components of firearm  250  (i.e., forward mounted on the barrel of firearm  250 ), PRFGB  200  could be positioned to be adjacent to (i.e., in relatively close proximity) the mechanical loading and ejection components of firearm  250 , or integrally (i.e., within the firearm receiver) to the mechanical loading and ejection components of the firearm. 
     The second exemplary embodiment of PRFGB  200  depicted in  FIGS. 2A-2C  is pressure based and venting is shown to be directly to atmosphere through side-, top-, or front-located relief ports of the PRFGB housing according to the subject matter disclosed herein. As depicted in  FIGS. 2A-2C , PRFGB  200  comprises a housing  205 , an operating piston  203 , a gas shut-off valve  207 , and a pressure relief mechanism comprising a relief piston  211 , a relief piston spring  212 , and a relief piston spring adjustment screw  213 . Housing  205  forms a gas cylinder  208 , which is a pressure chamber that is fluidly coupled to the bore  201   a  of barrel  201  through gas port  206  and gas shut-off valve  207 . During operation of firearm  250 , a bullet  204  is pushed down the bore  201   a  of the barrel  201  of the firearm by expanding high-pressure gas created from the burning of the gunpowder ( FIG. 2A ). 
     When bullet  204  passes first gas port  206  ( FIG. 2B ), a portion of the high-pressure gas passes through the first gas port  206 , through the gas shut-off valve  207  and enters the a gas cylinder  208 . The expanding gas pushes the operating piston  203  rearward (to the right in  FIGS. 2A-2C ) to cycle a firearm operating rod  202  or directly operate the firearm cartridge loading and ejecting mechanical components (bolt/bolt carrier)(not shown) if the piston assembly is located in the receiver of the firearm (not shown). 
     The increasing pressure formed by the expanding gas moves operating piston  203  rearward a certain distance, at which time the pressure reaches a designed pressure peak and the high-pressure gasses are then allowed to enter a transfer port  209  and impinge on the face of the relief piston  211 , which is part of the pressure relief mechanism. If the force of the gas pressure within the transfer port  209  pushing on the face  211   a  ( FIG. 2B ) of the relief piston  211  is less than the reacting force exerted by the relief piston spring  212  on relief piston  211 , no gas pressure will be relieved through relief port  210  (located on the front, side, or top of PRFGB housing  205 ), which is fluidly coupled between gas cylinder  208  and the bore  201   a  of barrel  201 . If the force of the gas pressure within transfer port  209  pushing on the face  211   a  of relief piston  211  is greater than the reacting force exerted by relief piston spring  212  on relief piston  211 , gas pressure will be relieved through relief portion  210 . The pressure at which gas is vented through the system can be adjusted by operation of relief piston spring adjustment screw  213 . In one exemplary embodiment, screwing in (i.e., clockwise) on relief piston spring adjustment screw  213  increases compressive force on relief piston spring  212  and relief piston  211 , thereby increasing the gas pressure required to move relief piston  211  to vent the high-pressure gas. In one exemplary embodiment, screwing out (i.e., counter-clockwise) on relief piston spring adjustment screw  213  decreases the compressive force on relief piston spring  212  and relief piston  211 , thereby decreasing the gas pressure required to move relief piston  211  in order to vent the high-pressure gas. In another exemplary embodiment, rotation direction of the adjustment can be reversed depending on design. In a situation in which venting high-pressure gas directly to the exterior of the firearm is not a life-and/or-safety compromising issue, relief portion  210  could be located in one exemplary embodiment on the side, front, or top of PRFGB housing  205 . 
     Once the rearward movement of the operating rod  202  reaches its physically limited movement ( FIG. 2C ), a recoil spring (not shown) moves operating rod  202  and operating piston  203  forward into their physically limited position in preparation for the next operating cycle. 
       FIGS. 3A-3C  respectively show different time periods of operation of a third exemplary embodiment of the Pressure-Regulating Firearm Gas Block (PRFGB) mounted on a “select fire” (i.e., selectably semi-automatic or fully-automatic) firearm according to the subject matter disclosed herein. In particular,  FIG. 3A  depicts a third exemplary embodiment of a PRFGB  300  and a firearm  350  through the barrel  301  of firearm  350  along a longitudinal axis  351  with a bullet  304  approaching a first gas port  306 .  FIG. 3B  depicts the third exemplary embodiment of a PRFGB  300  and a firearm  350  through the barrel  301  of firearm  350  along a longitudinal axis  351  with bullet  304  having passed first gas port  306  and blocking a second gas port  310  as the bullet travels toward the firearm flash arrestor/suppressor adapter  314 .  FIG. 3C  depicts the third exemplary embodiment of a PRFGB  300  and a firearm  350  through the barrel  301  of firearm  350  along a longitudinal axis  351  with bullet  304  exiting barrel  301  and flash arrestor/suppressor adapter  314 . It should be understood that only a portion of firearm  350  is depicted in  FIGS. 3A-3C . It should also be understood that in one exemplary embodiment, firearm  350  comprises a semi-automatic firearm, a fully automatic firearm, or a combination thereof. Additionally, it should be understood that while PRFGB  300  is depicted as being remote from the mechanical loading and ejection components of firearm  350  (i.e., forward mounted on the barrel of firearm  350 ), PRFGB  300  could be positioned to be adjacent to (i.e., in relatively close proximity) the mechanical loading and ejection components of firearm  350 , or integrally (i.e., within the firearm receiver) to the mechanical loading and ejection components of the firearm. 
     The third exemplary embodiment of PRFGB  300  is pressure based and venting is depicted to be directly into the barrel of the firearm through a bottom-located relief port of the PRFGB housing according to the subject matter disclosed herein. As depicted in  FIGS. 3A-3C , PRFGB  300  comprises a housing  305 , an operating piston  303 , a gas shut-off valve  307 , and a pressure relief mechanism comprising a relief piston  311 , a relief piston spring  312 , and a relief piston spring adjustment screw  313 . Housing  305  forms a gas cylinder  308 , which is a pressure chamber that is fluidly coupled to the bore  301   a  of barrel  301  through gas port  306  and gas shut-off valve  307 . During operation of firearm  350 , a bullet  304  is pushed down the barrel  301  of the firearm by expanding high-pressure gas created from the burning of the gunpowder ( FIG. 3A ). 
     When bullet  304  passes a first gas port  306 , a portion of the high-pressure gas passes through gas port  306 , through gas shut-off valve  307  and enters a gas cylinder  308 . The expanding gas pushes operating piston  303  rearward (to the right in  FIGS. 3A-3C ) to cycle firearm operating rod  302  or directly operate the firearm cartridge loading and ejecting mechanical components (bolt/bolt carrier)(not shown) if the piston assembly is located in the receiver of the firearm (not shown) which, in turn, cycles the firearm operating system. 
     The increasing pressure formed by the expanding gas moves operating piston  303  rearward a certain distance, at which time the pressure peaks at a designed pressure peak and the high-pressure gasses are then allowed to enter a transfer port  309  and impinge on the face  311   a  ( FIG. 3B ) of relief piston  311 , which is part of the pressure relief mechanism. If the force of the gas pressure within transfer port  309  pushing on the face  311   a  of relief piston  311  is less than the reacting force exerted by relief piston spring  312  on relief piston  311 , no gas pressure will be relieved through relief port  310 , which is fluidly coupled between gas cylinder  308  and the bore  301   a  of barrel  301 . If the force of the gas pressure within transfer port  309  pushing on the face  311   a  of relief piston  311  is greater than the reacting force exerted by relief piston spring  312  on relief piston  311 , gas pressure will be relieved through relief port  310 . The pressure at which gas is vented through the system can be adjusted by operation of relief piston spring adjustment screw  313 . In one exemplary embodiment, screwing in (i.e., clockwise) on relief piston spring adjustment screw  313  increases compressive force on relief piston spring  312  and relief piston  311 , thereby increasing the gas pressure required to move relief piston  311  to vent the high-pressure gas. In one exemplary embodiment, screwing out (i.e., counter-clockwise) on relief piston spring adjustment screw  313  decreases the compressive force on relief piston spring  312  and relief piston  311 , thereby decreasing the gas pressure required to move relief piston  311  to vent the high-pressure gas. In another exemplary embodiment, rotation direction adjustment can be reversed dependent on design. 
     Once the rearward movement of the operating rod  302  reaches its physically limited movement ( FIG. 3C ), a recoil spring (not shown) moves operating rod  302  and operating piston  303  forward into their physically limited position in preparation for the next operating cycle. 
     Due to the speed of bullet  304  relative to the speed of the high-pressure gas flowing through the system and amount of time required for the movement of operating piston  303 , operating rod  302 , and relief piston  311 , bullet  304  will have passed relief port  310  before relief piston  311  opens. The relative speed of bullet  304  compared to the speed of the gas and operating parts eliminates the possibility of gas flowing backwards through the system through relief port  310 . 
     The third exemplary embodiment (relief venting into the barrel) eliminates the visual and sound signatures of venting the relief gasses to atmosphere through the side or top of the PRFGB housing  305  during use of the firearm with a sound suppressor. During the use of firearms with suppressors due the efficiency of some modern firearm suppressors and ammunition, the operation of the mechanical components of the firearm makes more noise than the firing of the firearm. In a situation in which a soldier desires the lowest sound signature possible, gas shut-off valve  307  can be closed by inserting the tip (of a bullet) of a loaded cartridge into a protruding lever handle machined on the end of the rotating (circular) portion of the gas shut off valve  307  thereby stopping the semi-automatic or fully-automatic operation of the firearm. In this manner, the soldier needs no special tools or devices to close off the valve other than the ammunition he/she is using to fire the firearm. The firearm must then be manually cycled at a time when the soldier deems appropriate. 
       FIGS. 4A-4C  respectively show different time periods of operation of a fourth exemplary embodiment of the Pressure-Regulating Firearm Gas Block (PRFGB) mounted on a “select fire” (i.e., selectably semi-automatic or fully-automatic) firearm according to the subject matter disclosed herein. In particular,  FIG. 4A  depicts a fourth exemplary embodiment of a PRFGB  400  and a firearm  450  through the barrel  401  of firearm  450  along a longitudinal axis  451  with a bullet  404  approaching a first gas port  406 .  FIG. 4B  depicts the fourth exemplary embodiment of a PRFGB  400  and a firearm  450  through the barrel  401  of firearm  450  along a longitudinal axis  451  with bullet  404  having passed first gas port  406  as the bullet travels toward the firearm flash arrestor/suppressor adapter  414 .  FIG. 4C  depicts the fourth exemplary embodiment of a PRFGB  400  and a firearm  450  through the barrel  401  of firearm  450  along a longitudinal axis  451  with bullet  404  exiting barrel  401  and flash arrestor/suppressor adapter  414 . It should be understood that only a portion of firearm  450  is depicted in  FIGS. 4A-4C . It should also be understood that in one exemplary embodiment, firearm  450  comprises a semi-automatic firearm, a fully automatic firearm, or a combination thereof. Additionally, it should be understood that while PRFGB  400  is depicted as being remote from the mechanical loading and ejection components of firearm  450  (i.e., forward mounted on the barrel of firearm  450 ), PRFGB  400  could be positioned to be adjacent to (i.e., in relatively close proximity) the mechanical loading and ejection components of firearm  450 , or integrally (i.e., within the firearm receiver) to the mechanical loading and ejection components of the firearm. 
     The fourth exemplary embodiment of PRFGB  400  is pressure based and venting is depicted to be directly into a suppressor (silencer)(not shown) mounted to the forward portion of the barrel  401  of the firearm through the front relief port  412  of the PRFGB housing  405  according to the subject matter disclosed herein. As depicted in  FIGS. 4A-4C , PRFGB  400  comprises a housing  405 , an operating piston  403 , a gas shut-off valve  407 , and a pressure relief mechanism comprising a relief piston  409 , a relief piston spring  410 , and a relief piston spring adjustment screw  413 . Housing  405  forms two gas cylinders  408  and  416  of which cylinder  408  is a pressure chamber that is fluidly coupled to the bore  401   a  of barrel  401  through gas port  406  and gas shut-off valve  407 . During operation of firearm  450 , a bullet  404  is pushed down the barrel  401  of the firearm by expanding high-pressure gas created from the burning of the gunpowder ( FIG. 4A ). 
     When bullet  404  passes gas port  406 , a portion of the high-pressure gas passes through gas port  406 , through gas shut-off valve  407  and enters a gas cylinder  408 . If the force of the gas pressure within gas cylinder  408  pushing on the face  409   a  ( FIG. 4B ) of relief piston  409  is greater than the reacting force exerted by relief piston spring  410  on relief piston  409 , the relief piston  409  will move forward and compress the relief piston spring  410  so that gas pressure will be relieved through relief port  411  and  412 . In one exemplary embodiment, port  412  is capable of being fluidly coupled to a sound suppressor. The pressure at which gas is vented through the system can be adjusted by operation of relief piston spring adjustment screw  413 . During the time pressure is being vented (if pressures are greater than the preset pressure) a certain amount of gas is flowing through transfer port  415  into gas cylinder  416 . When the pressure in gas cylinder  408  drops to equal the preset pressure of the relief piston  409  and mating relief piston spring  410 , the relief piston moves rearward to seal off relief port  411  stopping the venting of gas pressure. Gas pressure continues to flow through transfer port  415  thereby increasing pressure in gas cylinder  416  to move the operating piston  403  rearward which in turn creates a rearward movement of the operating rod  402  to cycle the firearm loading and ejection mechanisms. Upon full stroke (rearward movement limit) the gas pressure in gas cylinder  416  is vented through relief port  417  which allows the forward movement of operating piston  403  and operating rod  402  under spring pressure to return to the forward limit against PRFGB housing  405 . 
     Conversely, when bullet  404  passes gas port  406 , a portion of the high-pressure gas passes through gas port  406 , through gas shut-off valve  407  and enters a gas cylinder  408 . If the force of the gas pressure within gas cylinder  408  pushing on the face  409   a  of relief piston  409  is less than the reacting force exerted by relief piston spring  410  on relief piston  409 , the relief piston  409  will not move to open up relief port  411  and gas pressure will not be relieved through relief port  411  and  412 . Gas will then flow through transfer port  415  into gas cylinder  416 . The increasing pressure formed by the expanding gas moves the operating piston  403  rearward which in turn creates a rearward movement of the operating rod  402  to cycle the firearm loading and ejection mechanisms or directly operate the firearm cartridge loading and ejecting mechanical components (bolt/bolt carrier) (not shown) if the piston assembly is located in the receiver of the firearm (not shown) which, in turn, cycles the firearm operating system. 
     In one exemplary embodiment, screwing in (i.e., clockwise) on relief piston spring adjustment screw  413  increases compressive force on relief piston spring  410  and relief piston  409 , thereby increasing the gas pressure required to move relief piston  409  to vent the high-pressure gas. In one exemplary embodiment, screwing out (i.e., counter-clockwise) on relief piston spring adjustment screw  413  decreases the compressive force on relief piston spring  410  and relief piston  409 , thereby decreasing the gas pressure required to move relief piston  409  to vent the high-pressure gas. In another exemplary embodiment, rotation direction adjustment can be reversed dependent on design. 
     Once the rearward movement of the operating rod  402  reaches its physically limited movement ( FIG. 4C ), a recoil spring (not shown) moves operating rod  402  and operating piston  303  forward into their physically limited position in preparation for the next operating cycle. 
     The fourth exemplary embodiment (relief venting into the suppressor) eliminates the visual and sound signatures of venting the relief gasses to atmosphere through the side or top of the PRFGB housing  405  during use of the firearm with a sound suppressor. During the use of firearms with suppressors due the efficiency of some modern firearm suppressors and ammunition, the operation of the mechanical components of the firearm makes more noise than the firing of the firearm. In a situation in which a soldier desires the lowest sound signature possible, gas shut-off valve  407  can be closed by inserting the tip (of a bullet) of a loaded cartridge into a protruding lever handle machined on the end of the rotating (circular) portion of the gas shut off valve  407  thereby stopping the semi-automatic or fully-automatic operation of the firearm. In this manner, the soldier needs no special tools or devices to close off the valve other than the ammunition he/she is using to fire the firearm. The firearm must then be manually cycled at a time when the soldier deems appropriate. 
       FIG. 5  depicts a cross-sectional side view of a fifth exemplary embodiment of a PRFGB  500 , a firearm  550  through the barrel  501  of the firearm along a longitudinal axis  551 , and a suppressor  580  according to the subject matter disclosed herein. It should be understood that only a portion of firearm  550  is depicted in  FIG. 5 . It should also be understood that in one exemplary embodiment, firearm  550  comprises a semi-automatic firearm, a fully automatic firearm, or a combination thereof. It should also be understood that PRFGB  500  operates substantially in accordance with the other exemplary embodiments disclosed herein. Suppressor  580  is coupled directly to PRFGB  500 . 
     During operation of firearm  550 , a bullet (not shown) is pushed down the bore  501   a  of a barrel  501  of firearm  550  by expanding high-pressure gas created from the burning of the gunpowder. When the bullet passes gas port  506 , a portion of the high-pressure gas passes through gas port  506  and enters a gas cylinder bringing gas to the rear face of a relief piston  509 . The expanding gas also pushes operating piston  503  rearward (toward the right in  FIG. 5 ) to cycle a firearm operating rod (not shown) or directly operate the firearm cartridge loading and ejecting mechanical components (bolt/bolt carrier)(not shown) if the piston assembly is located in the receiver of the firearm (not shown). 
     When the bullet passes gas port  506 , a portion of the high-pressure gas passes through gas port  506  and forces relief piston  509  back against the relief spring  510 . When the forces generated by the high-pressure gas on the rear face of relief piston  510  are balanced by the adjustable force of relief spring  510 , the desired gas pressure is allowed to flow through a transfer port  512 . The pressure cycles operating piston  503  rearward to operate the firearm action. If operating pressures are greater than the set pressure of relief spring  510  and piston assembly  503 , the excess pressure is vented through relief port  511  into a vent annulus  507  between barrel  501  and a suppressor mounting tube  584  and directed into a rear chamber  581  of sound suppressor  580 . The excess pressure is then vented through sound suppressor baffles  582  and to atmosphere through the sound suppressor muzzle  583 . 
     In an alternative exemplary embodiment, the PRFGB comprises a relief aperture on the front face of the PRFGB from which excess pressure is vented into a directly coupled aperture of a sound suppressor. When the suppressor is affixed to the gas block the vent hole of the gas block aligns with the vent inlet of the sound suppressor. In yet another alternative exemplary embodiment, the PRFGB comprises a relief aperture that is capable of venting excess pressure into the bore of the firearm and/or into a suppressor. 
     Although the foregoing disclosed subject matter has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced that are within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the subject matter disclosed herein is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.