Patent Publication Number: US-11047635-B2

Title: Semi-automatic shotgun and components thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/847,822, filed Dec. 19, 2017, which claims the benefit of U.S. Provisional Application No. 62/436,346, filed on Dec. 19, 2016, the disclosures of which are incorporated by reference herein in their entireties. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     Shotguns of any particular gauge may fire different shotshell cartridges with different payloads and propellant loads. With pump action shotguns the recycling occurs after the firing of the shotshell cartridges and occurs manually. Thus, there is no relation of the type of propellant load to the recycling reliability of the shotgun. In semiautomatic shotguns, the recycling occurs by bleeding off propellant gas from the barrel to actuate a piston connected to the breech block. The reliability of the cycling can be affected by the type of shotshell cartridge fired as well as the usable life of the shotgun. That is, a shotgun that reliably cycles for a magnum round that produces higher barrel pressures might not cycle for a lower powered skeet round with lower barrel pressures. And a shotgun that cycles for both a lower powered skeet round and a magnum powered round may subject the cycle mechanism components to higher forces causing premature failure of components. Improvement in versatility and reliability of semiautomatic shotguns when used with different powered shotshell cartridges would be welcome. 
     SUMMARY 
     A semiautomatic shotgun, the shotgun comprising a barrel, a cycling piston in a cylinder defining a piston chamber below the barrel, the barrel having a propellant gas diversion from a pair of ports in the barrel, through a pair of first gas passageways, into a pair of lateral chambers positioned on both sides of the barrel, each of the chambers having pressure relief valves therein. The chambers each further having a second gas passageways to the piston chamber for recycling the shotgun. 
     In embodiments, the second gas passageways is offset and nonlinear with the first gas pathway. The lateral chambers each having a cross sectional area greater than the first gas passageways and greater than the second gas passageways. 
     Embodiments of the shotgun provide a balanced reliable gas diversion system offering consistent cycling operation with different powered shotshell cartridges without the need for adjustment of the pressure relief valves. 
     In one or more embodiments, a semiautomatic shotgun comprises a receiver defining a receiver interior and a barrel attached to a forward portion of the receiver. The barrel has a barrel wall defining a barrel bore extending along a barrel axis of the barrel. The barrel wall defines a firing chamber that is dimensioned and configured to receiving a shell. A breech block is slidably received in the receiver interior. The breech block is movable between a forward position in which the breech block engages the breech end of the barrel for firing a chambered shell and a rearward position in which the breech block contacts a plunger of a spring loaded plunger assembly. In one or more embodiments, the spring loaded plunger assembly comprises the plunger, a first plunger spring, and a second plunger spring. In one or more embodiments, the first plunger spring defines a spring lumen and the second plunger spring is disposed inside the spring lumen defined by the first plunger spring. In one or more embodiments, a return spring  142  provides a return force urging the breech block toward the forward position. In one or more embodiments, a gas operated mechanism is disposed about the magazine tube and the gas operated mechanism comprises an annular shaped piston. In one or more embodiments, combustion gasses apply pressure to a forward facing surface of the annular shaped piston, the pressure applied to the annular shaped piston creates a rearward force, and the rearward force urges the breech block toward the rearward position. In one or more embodiments, a slider is disposed about the magazine tube at a location rearward of the annular shaped piston. In one or more embodiments, a port leg and a starboard leg extend between the slider and the breach block. In one or more embodiments, combustion gasses apply pressure to a forward facing surface of the annular shaped piston, the pressure applied to the annular shaped piston creates a rearward force, and the rearward force is transferred to the breech block by the sleeve, the starboard leg and the port leg. 
     In one or more embodiments, a semiautomatic shotgun comprises a receiver defining a receiver interior and a breech block that is slidably received in the receiver interior. The breech block is movable between a forward position in which the breech block engages the breech end of the barrel for firing a chambered shell and a rearward position in which the breech block is positioned rearward of the breech end of the barrel for discharging a spent shell. A barrel and a magazine tube extend forwardly from a forward portion of the receiver. The barrel has a breech end and a muzzle end. A barrel wall of the barrel extends between the breech end and the muzzle end. The barrel wall defines a barrel bore extending along a barrel axis of the barrel. The barrel wall defines a firing chamber and barrel bore, the firing chamber being dimensioned and configured to receiving a shell. The magazine tube has a rearward end and a forward end. A magazine wall of the magazine tube extends between the rearward end and the forward end. The magazine wall defines a magazine tube bore extending along a magazine axis of the magazine tube. The barrel axis and the magazine axis are parallel and define a vertical plane. 
     A semiautomatic shotgun in accordance with the embodiments described in the preceding paragraph may further include a gas block assembly including a gas block that is disposed about the magazine tube with the magazine tube extending through the block bore defined by the gas block. The gas block assembly includes a starboard regulator assembly and a port regulator assembly. The gas block defines a starboard regulator cavity and a port regulator cavity. The starboard regulator cavity extends along a starboard regulator axis and the port regulator cavity extends along a port regulator axis. The starboard regulator axis and the port regulator axis define a horizontal plane. In one or more embodiments, the horizontal plane defined by the starboard regulator axis and the port regulator axis is perpendicular to the vertical plane defined by the barrel axis and the magazine axis. In one or more embodiments, the starboard regulator assembly and the starboard regulator cavity are disposed starboard of the vertical plane defined by the barrel axis and the magazine axis. In one or more embodiments, the starboard regulator assembly and the starboard regulator cavity are disposed below the barrel axis and above the magazine axis. In one or more embodiments, the port regulator assembly and the port regulator cavity are disposed portward of the vertical plane defined by the barrel axis and the magazine axis. In one or more embodiments, the port regulator assembly and the port regulator cavity are disposed below the barrel axis and above the magazine axis. 
     A semiautomatic shotgun in accordance with the embodiments described in the preceding paragraph may further include a sleeve comprising a sleeve wall extending into the block bore defined by a gas block with a portion of the sleeve disposed between an outer surface of the magazine tube and inner surface of the gas block. In one or more embodiments, the magazine tube, the sleeve, and the gas block cooperate to define an annular volume. The annular volume communicates with the barrel bore so that combustion gasses can enter the annular volume. The starboard regulator assembly acts to release combustion gasses when the combustion gasses in the barrel bore and/or the annular volume reaches a first predetermined pressure. The port regulator assembly acts to release combustion gasses when the combustion gasses in the barrel bore and/or the annular volume reaches a first predetermined pressure. In one or more embodiments, the first predetermined pressure and the second predetermined pressure are different. In one or more embodiments, the first predetermined pressure is selected to correspond to a first shotshell load and the second predetermined pressure is selected to correspond to a second shotshell load. In one or more embodiments, the first predetermined pressure and the second predetermined pressure are substantially equal. In one or more embodiments, the first predetermined pressure and the second predetermined pressure have values within about ten percent of one another. 
     A semiautomatic shotgun in accordance with one or more embodiments comprises a receiver, a barrel and a magazine tube. The barrel and the magazine tube both extend forward beyond a forward end of the receiver with the magazine tube being located below the barrel. In an embodiment, a gas operated mechanism is disposed about the magazine tube. In an embodiment, the gas operated mechanism comprises a gas block assembly that including an annular shaped piston. In an embodiment, the annular shaped piston extends into a block bore defined by a gas block of the gas block assembly. In an embodiment, the block bore extends along a block bore axis. In an embodiment, the gas block assembly includes a starboard regulator housing defining starboard regulator cavity that extends along a starboard regulator axis. In an embodiment, the starboard regulator housing comprises a first starboard male thread and the first starboard male thread is disposed in threaded engagement with a first starboard female thread of the gas block. In an embodiment, a starboard valve member is disposed in the starboard regulator cavity with a seating surface of the starboard valve member is biased to seat against a complementary surface of the starboard regulator housing by a starboard spring. In an embodiment, a forward end of the starboard spring seats against the starboard valve member and a rearward end of the starboard spring seats against a starboard retainer. In an embodiment, the starboard retainer comprises a second starboard male thread and the second starboard male thread is disposed in threaded engagement with a second starboard female thread of the starboard regulator housing. In an embodiment, the gas block assembly includes a port regulator housing defining port regulator cavity that extends along a port regulator axis. In an embodiment, the port regulator housing comprises a first port male thread and the first port male thread is disposed in threaded engagement with a first port female thread of the gas block. In an embodiment, a port valve member is disposed in the port regulator cavity with a seating surface of the port valve member is biased to seat against a complementary surface of the port regulator housing by a port spring. In an embodiment, a forward end of the port spring seats against the port valve member and a rearward end of the port spring seats against a port retainer. In an embodiment, the port retainer comprises a second port male thread and the second port male thread is disposed in threaded engagement with a second port female thread of the port regulator housing. In an embodiment, the starboard regulator axis, the port regulator axis, and the block bore axis define a triangular prism comprising a first base, a second base and three side faces. In an embodiment, the starboard regulator axis and the block bore axis define a first plane and a first side face of the triangular prism lies in the first plane. In an embodiment, the port regulator axis and the block bore axis define a second plane and a second side face of the triangular prism lies in the second plane. In an embodiment, the starboard regulator axis and the port regulator axis define a third plane and a third side face of the triangular prism lies in the third plane. 
     A semiautomatic shotgun in accordance with one or more embodiments comprises a receiver defining a receiver interior and a barrel attached to a forward portion of the receiver. The barrel has a breech end and a muzzle end. A barrel wall of the barrel extends between the breech end and the muzzle end. The barrel wall defines a barrel bore extending along a longitudinal axis of the barrel. The barrel wall defines a firing chamber with the barrel bore, the firing chamber being dimensioned and configured to receiving a shell. 
     In one or more embodiments, a breech block is slidably received in the receiver interior. The breech block is movable between a forward position in which the breech block engages the breech end of the barrel for firing a chambered shell and a rearward position in which the breech block is positioned rearward of the breech end of the barrel for discharging a spent shell. A magazine tube is attached to a forward portion of the receiver. The magazine tube has a rearward end and a forward end. A magazine wall of the magazine tube extends between the rearward end and the forward end. The magazine wall defines a magazine tube bore extending along a longitudinal axis of the magazine tube. 
     In one or more embodiments, the semiautomatic shotgun includes a sleeve having a circular or tubular shape and comprising a sleeve wall. The sleeve wall having an outer surface and an inner surface. The inner surface of the sleeve wall defining a lumen. The sleeve is positioned so that the sleeve wall encircles the magazine tube with the magazine tube extending through the lumen. The sleeve has a rearward end and a forward end. A first sealing ring is disposed between the inner surface of the sleeve and an outer surface of the magazine tube. In embodiments addition sealing rings may be placed between the inner surface of the sleeve and an outer surface of the magazine tube. One or more second sealing rings may be disposed between the outer surface of the sleeve and an inner facing bore surface of the gas block. The space between the inner facing surface of the gas block and the outer surface of the magazine tube defining an annular expansion chamber and the sleeve defining an annular piston. 
     In one or more embodiments, the gas block defines a channel and an upward facing opening fluidly communicating with the channel. The barrel extends into the channel. In one or more embodiments, the gas block is fixed to the barrel. The gas block has a rearward end and a forward end. The gas block has a body extending in a forward direction from the rearward end to the forward end and extending in a rearward direction from the forward end to the rearward end. The body of the gas block defines a pair of chambers, a starboard regulator cavity and a port regulator cavity. 
     In one or more embodiments, the starboard regulator cavity comprises a forward starboard bore, a rearward starboard bore and a starboard step or shoulder defining a valve seat between the forward starboard bore and the rearward starboard bore. The forward starboard bore extends in the forward direction away from the starboard valve seat. The starboard rearward bore extends in the rearward direction away from the starboard valve seat. The forward starboard bore is defined by a forward bore surface of the gas block. The rearward starboard bore is defined by a rearward bore surface. The starboard valve seat comprises a starboard valve seat surface extending between the forward starboard bore surface and the starboard rearward bore surface. The forward starboard bore has a first diameter, the starboard rearward bore has a second diameter. In one or more embodiments, the second diameter is greater than the first diameter. The forward starboard bore surface meets the starboard valve seat surface at an edge. A starboard valve member is disposed in the starboard regulator cavity. A seating surface of the starboard valve member is biased to seat against the edge by a starboard spring. A starboard guide extends through a lumen defined by the starboard spring and into a starboard pocket defined by the starboard valve member. 
     In one or more embodiments, the starboard forward bore of the starboard regulator cavity fluidly communicates with the barrel bore via a starboard passageway defined by the gas block and a starboard hole defined by the barrel. The forward starboard bore of the starboard regulator cavity fluidly communicates with the annular volume via a starboard aperture. Upon firing a shell with the shotgun, combustion gasses within the barrel enter the annular volume via the starboard hole and the port hole to move the sleeve and a slider rearward for cycling a mechanism disposed in the receiver interior. 
     In one or more embodiments, the semiautomatic shotgun includes a slider comprising a slider wall. The slider wall has an outer surface and an inner surface with the inner surface defining a lumen. The slider is positioned so that the slider wall encircles the magazine tube and the magazine tube extends through the lumen. The slider having a rearward end and a forward end. The slider wall extends between the rearward end and the forward end. A slider assembly includes the slider and a starboard leg having a forward end and a rearward end. A portion of the starboard leg proximate the forward end is fixed to the slider. A portion of the starboard leg proximate the rearward end engages the mechanism disposed inside the receiver interior. The slider assembly also includes a port leg having a forward end and a rearward end. A portion of the port leg proximate the forward end is fixed to the slider. A portion of the port leg proximate the rearward end engages the mechanism disposed inside the receiver interior. 
     A feature and advantage of embodiments of the invention is that the two regulators can be adjusted to have different pressure relief points wherein considering restricted volumetric passages to each, one may release for a certain barrel pressure, for example for a lowered powered cartridge, and the other does not release. And wherein for a higher pressure cartridge, both regulators may release. 
     A feature and advantage of embodiments is a tandem pair of regulators that operate a different relief pressures. 
     A feature and advantage of embodiments is a tandem pair of regulators that have different sized volumetrically. 
     A feature and advantage of embodiments is a tandem pair of regulators that have the same sizes volumetrically and have different spring forces providing different pressure release points. 
     A feature and advantage of embodiments is a tandem pair of regulators that have the same sizes volumetrically and have different sizes of valve members and valve seats. 
     A feature and advantage of embodiments is a tandem pair of regulators that operate at the same relief pressure and offer redundancy in operation. 
     A feature and advantage of embodiments is a semiautomatic shotgun that reliably cycles shotshells of different propellant loads. 
     A feature and advantage of embodiments is a semiautomatic shotgun with an adjustable pressure relief valve, in embodiments, two adjustable relief valves. 
     A feature and advantage of embodiments is a semiautomatic shotgun that provides dual pressure relief valves adding reliability, redundancy, and a compact form factor. Moreover, the gas from the propellant is provided to the piston in a more balanced manner than conventional gas operated shotguns. 
     The above summary is not intended to describe each illustrated embodiment or every implementation of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The drawings included in the present application are incorporated into, and form part of, the specification. They illustrate embodiments of the present disclosure and, along with the description, serve to explain the principles of the disclosure. The drawings are only illustrative of certain embodiments and do not limit the disclosure. 
         FIG. 1A  is a side elevation view showing a shotgun in accordance with an embodiment described in the detailed description. 
         FIG. 1B  is a partially exploded side view of the shotgun shown in  FIG. 1A . 
         FIG. 2  is an exploded side view of the shotgun shown in  FIG. 1A . 
         FIG. 3A  is an enlarged side view of the shotgun shown in  FIG. 1B . 
         FIG. 3B  is an enlarged side view further illustrating a portion of the shotgun shown in  FIG. 3A . 
         FIG. 4  is a perspective, exploded view of a gas block assembly in accordance with an embodiment described in the detailed description. 
         FIG. 5  is an additional perspective, exploded view of the gas block assembly shown in  FIG. 4 . 
         FIG. 6A  is a perspective view of a sleeve assembly in accordance with an embodiment described in the detailed description. 
         FIG. 6B  is a perspective, exploded view of the sleeve assembly shown in  FIG. 6A . 
         FIG. 7  is a cross-sectioned perspective view of a gas block in accordance with an embodiment described in the detailed description. 
         FIG. 8A  is an end view showing a gas block assembly and a section line. 
         FIG. 8B  is a cross-sectioned perspective view of a gas block assembly in accordance with an embodiment described in the detailed description. 
         FIG. 9  is an enlarged cross-sectioned perspective view further illustrating a portion of the gas block assembly shown in  FIG. 8B . 
         FIG. 10A  is a side view showing a gas block assembly and a section line. 
         FIG. 10B  is a cross-sectioned perspective view of a gas block assembly in accordance with an embodiment described in the detailed description. 
         FIG. 11  is a cross-sectioned perspective view of a gas block in accordance with an embodiment described in the detailed description. 
         FIG. 12  is a cross-sectional view of a barrel and a gas block in accordance with an embodiment described in the detailed description. 
         FIG. 13A  is a front view showing a gas block assembly and a section line. 
         FIG. 13B  is a cross-sectioned perspective view of the gas block assembly shown in  FIG. 13A  with the cross-sectioning being performed along the section line shown in  FIG. 13A . 
         FIG. 13C  is a front view showing a gas block assembly and a section line. 
         FIG. 13D  is a cross-sectioned perspective view of the gas block assembly shown in  FIG. 13C  with the cross-sectioning being performed along the section line shown in  FIG. 13C . 
         FIG. 14  is a perspective view showing a shotgun in accordance with an embodiment described in the detailed description. 
         FIG. 15A  is a side elevation view showing a shotgun in accordance with an embodiment described in the detailed description. 
         FIG. 15B  is a partially exploded side view of the shotgun shown in  FIG. 1A . 
         FIG. 16A  is an enlarged side view of the shotgun shown in  FIG. 15B . 
         FIG. 16B  is an enlarged side view further illustrating a portion of the shotgun shown in  FIG. 16A . 
         FIG. 17  is an exploded side view of the shotgun shown in  FIG. 15A  and  FIG. 15B . 
         FIG. 18A  is a perspective view of an assembly including a receiver and a breech block. 
         FIG. 18B  is a perspective view of the assembly of  FIG. 18A  with the breech block removed. 
         FIG. 19A  is a side view of an assembly including a receiver and a breech block. The breech block is disposed in a forward position in the embodiment of  FIG. 19A . 
         FIG. 19B  is a side view of an assembly including a receiver and a breech block. The breech block is shown in an intermediate position in  FIG. 19C . The intermediate position is between the forward position and the rearward position. 
         FIG. 19C  is a side view of an assembly including a receiver and a breech block. The breech block is disposed in a rearward position in the embodiment of  FIG. 19C . 
         FIG. 19D  is a side view of an assembly including a receiver and a breech block. The breech block is disposed in a forward position in the embodiment of  FIG. 19D . 
         FIG. 20A  is a perspective view showing an assembly including a stock rod and a spring loaded plunger assembly. 
         FIG. 20B  is a side view showing an assembly comprising a spring loaded plunger assembly including a plunger and a plunger housing. 
         FIG. 20C  is a cross-sectional view further illustrating the stock rod and the spring loaded plunger assembly shown in  FIG. 20A  and  FIG. 20B . 
         FIG. 20D  is an enlarged cross-sectional view further illustrating the spring loaded plunger assembly shown in  FIG. 20C . 
         FIG. 20E  is an exploded view further illustrating the stock rod and the spring loaded plunger assembly shown in  FIG. 20A  through  FIG. 20D . 
         FIG. 20F  is a cross-sectional view further illustrating the stock rod and the spring loaded plunger assembly in accordance with an additional embodiment. 
         FIG. 20G  is an enlarged cross-sectional view further illustrating the spring loaded plunger assembly shown in  FIG. 20F . 
         FIG. 21  is an exploded perspective view showing an assembly. 
         FIG. 22  is an exploded perspective view showing an assembly including the assembly of  FIG. 21 . 
         FIG. 23  is an exploded perspective view showing the assembly of  FIG. 22  from another viewing angle. 
         FIG. 24A  is an isometric view showing an assembly. 
         FIG. 24B  is an isometric view showing an assembly. 
         FIG. 25A  is a front view showing an assembly. 
         FIG. 25B  is a side view showing an assembly. 
         FIG. 25C  is a top view showing an assembly. 
     
    
    
     While embodiments of the disclosure are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure. 
     DETAILED DESCRIPTION 
     Referring, for example, to  FIGS. 14-20F , a semiautomatic shotgun  10  in accordance with one or more embodiments comprises a receiver  32  defining a receiver interior  34  and a barrel  20  attached to a forward portion of the receiver  32 . The shotgun is particularly suited for firing shotshells  33  of different power levels. The barrel  20  has a barrel wall  30  defining a barrel bore  22  extending along a barrel axis  24  of the barrel  20 . The barrel wall  30  defines a firing chamber that is dimensioned and configured to receiving the shells of different power levels. A breech block  38  is slidably received in the receiver interior  34 . The breech block  38  is movable between a forward position in which the breech block  38  engages the breech end  28  of the barrel  20  for firing a chambered shell and a rearward position in which the breech block  38  contacts a plunger  52  of a spring loaded plunger assembly  50 . In one or more embodiments, the spring loaded plunger assembly  50  comprises the plunger  52 , a first coil spring  82 , and a second coil spring  84 . In one or more embodiments, the first coil spring  82  defines a spring lumen  80  and the second coil spring  84  is disposed inside the spring lumen  80  defined by the first coil spring  82 . In one or more embodiments, a return spring provides a return force urging the breech block  38  toward the forward position. In one or more embodiments, a gas operated mechanism  36  is disposed about the magazine tube  120  and the gas operated mechanism  36  comprises an annular shaped piston  250 . In one or more embodiments, combustion gasses apply pressure to a forward facing surface of the annular shaped piston  250 , the pressure applied to the annular shaped piston creates a rearward force, and the rearward force urges the breech block  38  toward the rearward position. In one or more embodiments, a slider  150  is disposed about the magazine tube  120  at a location rearward of the annular shaped piston  250 . In one or more embodiments, a port leg  166  and a starboard leg  164  extend between the slider  150  and the breach block  38 . In one or more embodiments, combustion gasses apply pressure to a forward facing surface of the annular shaped piston  250 , the pressure applied to the annular shaped piston creates a rearward force, and the rearward force is transferred to the breech block  38  by the sleeve, the starboard leg  164  and the port leg  166 . 
     Referring, for example, to  FIGS. 14 and 21-25B  a semiautomatic shotgun  10  in accordance with one or more embodiments comprises a receiver  32 , a barrel  20  and a magazine tube  120 . The barrel  20  and the magazine tube  120  both extend forward beyond a forward end of the receiver  32  with the magazine tube  120  being located below the barrel  20 . A gas operated mechanism  36  is disposed about the magazine tube  120 . In one or more embodiments, the gas operated mechanism  36  comprises an annular shaped piston  250  and gas block assembly  200 . The gas block having a rearward body portion  240  defining a lumen and two forwardly extending tubular extensions comprising a starboard tubular extension  338  and a port tubular extension  438  defining a starboard regulator cavity  322  and a port regulator cavity  422  respectively. In one or more embodiments, the semiautomatic shotgun  10  includes a starboard regulator assembly  320  disposed in the starboard regulator cavity  322  and a port regulator assembly disposed in the port regulator cavity. The semiautomatic shotgun  10  may also include a breech block  38  that is slidably received in the receiver interior  34 . In one or more embodiments, the breech block  38  is movable between a forward position in which the breech block  38  engages the breech end  28  of the barrel  20  for firing a chambered shell, and a rearward position in which the breech block  38  contacts a plunger  52  of a spring loaded plunger assembly  50 . A rearward force produced by the gas block assembly  200  urges the breech block  38  toward the rearward position. 
     Referring, for example, to  FIGS. 1, 3A and 12 , a semiautomatic shotgun  10  in accordance with one or more embodiments comprises a receiver  32  defining a receiver interior  34  and a breech block  38  that is slidably received in the receiver interior  34 . The breech block  38  is movable between a forward position in which the breech block  38  engages the breech end  28  of the barrel  20  for firing a chambered shell and a rearward position in which the breech block  38  is positioned rearward of the breech end  28  of the barrel  20  for discharging a spent shell. A barrel  20  and a magazine tube  120  extend forwardly from a forward portion of the receiver  32 . The barrel  20  has a breech end  28  and a muzzle end  26 . A barrel wall  30  of the barrel  20  extends from the breech end  28  to the muzzle end  26 . The barrel wall  30  defines a barrel bore  22  extending along a barrel axis  24  of the barrel  20 . The barrel wall  30  defines a firing chamber and barrel bore  22 , the firing chamber being dimensioned and configured to receiving a shell. The magazine tube  120  has a rearward end and a forward end. A magazine wall  130  of the magazine tube  120  extends between the rearward end and the forward end. The magazine wall  130  defines a magazine tube bore extending along a magazine axis of the magazine tube  120 . The barrel axis  24  and the magazine axis  140  define a vertical plane. 
     A semiautomatic shotgun in accordance with the embodiments described in the preceding paragraph may further include a gas block assembly  200  including a gas block  220  that is disposed about the magazine tube  120  with the magazine tube  120  extending through the block bore  222  defined by the gas block  220 . The gas block assembly  200  includes a starboard regulator assembly  320  and a port regulator assembly  420 . The gas block  220  defines a starboard regulator cavity  322  and a port regulator cavity  422 . The starboard regulator cavity  322  extends along a starboard regulator axis  340  and the port regulator cavity  422  extends along a port regulator axis  440 . The starboard regulator axis  340  and the port regulator axis  440  define a horizontal plane. In one or more embodiments, the horizontal plane defined by the starboard regulator axis  340  and the port regulator axis  440  is perpendicular to the vertical plane defined by the barrel axis  24  and the magazine axis  140 . In one or more embodiments, the starboard regulator assembly  320  and the starboard regulator cavity  322  are disposed starboard of the vertical plane defined by the barrel axis  24  and the magazine axis  140 . In one or more embodiments, the starboard regulator assembly  320  and the starboard regulator cavity  322  are disposed below the barrel axis  24  and above the magazine axis  140 . In one or more embodiments, the port regulator assembly  420  and the port regulator cavity  422  are disposed portward of the vertical plane defined by the barrel axis  24  and the magazine axis  140 . In one or more embodiments, the port regulator assembly  420  and the port regulator cavity  422  are disposed below the barrel axis  24  and above the magazine axis  140 . 
     A semiautomatic shotgun in accordance with the embodiments described in the preceding paragraph may further include a sleeve  252  comprising a sleeve wall  262  extending into the block bore  222  defined by a gas block  220  with a portion of the sleeve  252  disposed between an outer surface of the magazine tube  120  and inner surface of the gas block  220 . In one or more embodiments, the magazine tube  120 , the sleeve  252 , and the gas block  220  cooperate to define an annular volume  264 . The annular volume  238  communicates with the barrel bore  22  so that combustion gasses can enter the annular volume  238 . The starboard regulator assembly  320  acts to release combustion gasses when the combustion gasses in the barrel bore  22  and/or the annular volume  238  reaches a first predetermined pressure. The port regulator assembly  420  acts to release combustion gasses when the combustion gasses in the barrel bore  22  and/or the annular volume  238  reaches a first predetermined pressure. In one or more embodiments, the first predetermined pressure and the second predetermined pressure are different. In one or more embodiments, the first predetermined pressure is selected to correspond to a first shotshell load and the second predetermined pressure is selected to correspond to a second shotshell load. In one or more embodiments, the first predetermined pressure and the second predetermined pressure are substantially equal. In one or more embodiments, the first predetermined pressure and the second predetermined pressure have values within 10% of one another. 
     Referring, for example, to  FIGS. 16-25B , a semiautomatic shotgun  10  in accordance with one or more embodiments comprises a receiver  32 , a barrel  20  and a magazine tube  120 . The barrel  20  and the magazine tube  120  both extend forward beyond a forward end of the receiver  32  with the magazine tube  120  being located below the barrel  20 . In an embodiment, a gas operated mechanism  36  is disposed about the magazine tube  120 . In an embodiment, the gas operated mechanism  36  comprises a gas block assembly  200  that including an annular shaped piston  250 . In an embodiment, the annular shaped piston  250  extends into a block bore  222  defined by a gas block  220  of the gas block assembly  200 . In an embodiment, the block bore  222  extends along a block bore axis  224 . In an embodiment, the gas block assembly  200  includes a starboard regulator housing  338  defining starboard regulator cavity  322  that extends along a starboard regulator axis  340 . In an embodiment, the starboard regulator housing  338  comprises a first starboard male thread  362  and the first starboard male thread  362  is disposed in threaded engagement with a first starboard female thread  364  of the gas block  220 . In an embodiment, a starboard valve member  330  is disposed in the starboard regulator cavity  322  with a seating surface of the starboard valve member  330  is biased to seat against a complementary surface of the starboard regulator housing  338  by a starboard spring  332 . In an embodiment, a forward end of the starboard spring  332  seats against the starboard valve member  330  and a rearward end of the starboard spring  332  seats against a starboard retainer  336 . In an embodiment, the starboard retainer  336  comprises a second starboard male thread  366  and the second starboard male thread  366  is disposed in threaded engagement with a second starboard female thread  368  of the starboard regulator housing  338 . In an embodiment, the gas block assembly  200  includes a port regulator housing  438  defining port regulator cavity  422  that extends along a port regulator axis  440 . In an embodiment, the port regulator housing  438  comprises a first port male thread  462  and the first port male thread  462  is disposed in threaded engagement with a first port female thread  464  of the gas block  220 . In an embodiment, a port valve member  430  is disposed in the port regulator cavity  422  with a seating surface of the port valve member  430  is biased to seat against a complementary surface of the port regulator housing  438  by a port spring  432 . In an embodiment, a forward end of the port spring  432  seats against the port valve member  430  and a rearward end of the port spring  432  seats against a port retainer  436 . In an embodiment, the port retainer  436  comprises a second port male thread  466  and the second port male thread  466  is disposed in threaded engagement with a second port female thread  468  of the port regulator housing  438 . In an embodiment, the starboard regulator axis  340 , the port regulator axis  440 , and the block bore axis  224  define a triangular prism comprising a first base, a second base and three side faces. In an embodiment, the starboard regulator axis  340  and the block bore axis  224  define a first plane P 1  and a first side face of the triangular prism lies in the first plane P 1 . In an embodiment, the port regulator axis  440  and the block bore axis  224  define a second plane P 2  and a second side face of the triangular prism lies in the second plane P 2 . In an embodiment, the starboard regulator axis  340  and the port regulator axis  440  define a third plane P 3  and a third side face of the triangular prism lies in the third plane P 3 . 
     Referring, for example, to  FIGS. 1A-3B and 12 , a semiautomatic shotgun  10  in accordance with one or more embodiments comprises a receiver  32  defining a receiver interior  34  and a barrel  20  attached to a forward portion of the receiver  32 . The barrel  20  has a breech end  28  and a muzzle end  26 . A barrel wall  30  of the barrel  20  extends from the breech end  28  to the muzzle end  26 . The barrel wall  30  defines a barrel bore  22  extending along a longitudinal axis of the barrel  20 . The barrel wall  30  defines a firing chamber and barrel bore  22 , the firing chamber being dimensioned and configured to receiving a shell. 
     A breech block  38  is slidably received in the receiver interior  34 . The breech block  38  is movable between a forward position in which the breech block  38  engages the breech end  28  of the barrel  20  for firing a chambered shell and a rearward position in which the breech block  38  is positioned rearward of the breech end  28  of the barrel  20  for discharging a spent shell. A magazine tube  120  is attached to a forward portion of the receiver  32 . The magazine tube  120  has a rearward end and a forward end. A magazine wall  130  of the magazine tube  120  extends between the rearward end and the forward end. The magazine wall  130  defines a magazine tube bore extending along a longitudinal axis of the magazine tube  120 . 
     The semiautomatic shotgun  10  includes a sleeve  252  comprising a sleeve wall  262 . The sleeve wall  262  extending between an outer surface and an inner surface. The inner surface of the sleeve wall  262  defines a lumen  254 . The sleeve  252  is positioned so that the sleeve wall  262  encircles the magazine tube  120  with the magazine tube  120  extending through the lumen  254 . The sleeve  252  has a rearward end and a forward end. The sleeve wall  262  extends between the forward end and the rearward end. A first sleeve ring  230  is disposed between an inner surface of the sleeve  252  and an outer surface of the magazine tube  120 . The first sleeve ring  230  defines a slit  244 . 
     The semiautomatic shotgun  10  includes a gas block assembly  200  with regulators or pressure relief valves  202 ,  204 . The gas block  220  defining a block bore  222 . The magazine tube  120  extends through the block bore  222  defined by the gas block  220 . The block bore  222  may extend along a block bore axis  224 . The sleeve  252  extends into the block bore  222  defined by a gas block  220  with a portion of the sleeve  252  being disposed between an outer surface of the magazine tube  120  and inner surface of the gas block  220 . A second sleeve ring  232  is disposed between an outer surface of the sleeve  252  and an inner surface of the gas block  220 . The second sleeve ring  232  defining a slot  242 . The magazine tube  120 , the sleeve  252 , and the gas block  220  cooperate to define an annular volume  264 . A stop ring  234  is received in the lumen defined by the sleeve wall  262 . 
     The gas block  220  defines a channel  240  and an upward facing opening fluidly communicating with the channel  240 . The barrel  20  extends into the channel  240 . In one or more embodiments, the gas block  220  is fixed to the barrel  20 . The gas block  220  has a rearward end and a forward end. The gas block  220  has a body  246  extending in a forward direction from the rearward end to the forward end and extending in a rearward direction from the forward end to the rearward end. The body  246  of the gas block  220  defines a starboard regulator cavity  322  and a port regulator cavity  422 . 
     The starboard regulator cavity  322  comprises a forward starboard bore  335 , a rearward starboard bore  338  and a starboard valve seat  346  disposed between the forward starboard bore  335  and the rearward starboard bore  338 . The forward starboard bore  335  extends in the forward direction away from the starboard valve seat  346 . The rearward starboard bore  338  extends in the rearward direction away from the starboard valve seat  346 . The forward starboard bore  335  is defined by a forward starboard bore surface  340  of the gas block  220 . The rearward starboard bore  338  is defined by a rearward starboard bore surface  342 . The starboard valve seat  346  comprises a starboard valve seat surface  348  extending between the forward starboard bore surface  340  and the rearward starboard bore surface  342 . The forward starboard bore  335  has a first diameter, the rearward starboard bore  338  has a second diameter. In one or more embodiments, the second diameter is greater than the first diameter. The forward starboard bore surface  340  meets the starboard valve seat surface  348  at a starboard edge  344 . A starboard valve member  330  is disposed in the starboard regulator cavity  322 . A seating surface of the starboard valve member  330  is biased to seat against the starboard edge  344  by a starboard spring  332 . A starboard guide  334  extends through a lumen defined by the starboard spring  332  and into a starboard valve member pocket  352  defined by the starboard valve member  330 . 
     The forward starboard bore  335  of the starboard regulator cavity  322  fluidly communicates with the barrel bore  22  via a starboard first passageway  354  defined by the gas block  220  and a starboard hole  50  defined by the barrel  20 . The forward starboard bore  335  of the starboard regulator cavity  322  fluidly communicates with the annular volume  264  via a starboard aperture  350 . Upon firing a shell with the shotgun, combustion gasses within the barrel  20  enter the annular volume via the starboard hole  50  and the port hole  52  to move the sleeve  252  and a slider  150  rearward for cycling a mechanism  36  disposed in the receiver interior  34 . 
     The slider  150  comprising a slider wall  160 . The slider wall  160  has an outer surface and an inner surface with the inner surface defining a lumen. The slider  150  is positioned so that the slider wall  160  encircles the magazine tube  120  and the magazine tube  120  extends through the lumen. The slider  150  having a rearward end and a forward end. The slider wall  160  extends between the rearward end and the forward end. A slider assembly  161  includes the slider  150  and a starboard leg  162  having a forward end and a rearward end. A portion of the starboard leg  162  proximate the forward end is fixed to the slider  150 . A portion of the starboard leg  162  proximate the rearward end engages the mechanism  36  disposed inside the receiver interior  34 . The slider assembly  161  also includes a port leg  164  having a forward end and a rearward end. A portion of the port leg  164  proximate the forward end is fixed to the slider  150 . A portion of the port leg  164  proximate the rearward end engages the mechanism  36  disposed inside the receiver interior  34 . The semiautomatic shotgun  10  also includes a trigger  40 , a trigger guard  42 , a buttstock  44 , a fore stock  46  and a cap  48 . 
     The port regulator cavity  422  comprises a forward port bore  435 , a rearward port bore  438  and a port valve seat  446  disposed between the forward port bore  435  and the rearward port bore  438 . The forward port bore  435  extends in the forward direction away from the port valve seat  446 . The rearward port bore  438  extends in the rearward direction away from the port valve seat  446 . The forward port bore  435  is defined by a forward port bore surface  440  of the gas block  220 . The rearward port bore  438  is defined by a rearward port bore surface  442 . The port valve seat  446  comprises a port valve seat surface  448  extending between the forward port bore surface  440  and the rearward port bore surface  442 . The forward port bore  435  has a first diameter, the rearward port bore  438  has a second diameter. In one or more embodiments, the second diameter is greater than the first diameter. The forward port bore surface  440  meets the port valve seat surface  448  at a port edge  444 . A port valve member  430  is disposed in the port regulator cavity  422 . A seating surface of the port valve member  430  is biased to seat against the port edge  444  by a port spring  432 . A port guide  434  extends through a lumen defined by the port spring  432  and into a port valve member pocket  452  defined by the port valve member  430 . 
     The forward port bore  435  of the port regulator cavity  422  fluidly communicates with the barrel bore  22  via a port passageway  454  defined by the gas block  220  and a port hole  52  defined by the barrel  20 . The forward port bore  435  of the port regulator cavity  422  fluidly communicates with the annular volume  264  via a port aperture  450 . Upon firing a shell with the shotgun, combustion gasses within the barrel  20  enter the annular volume via the port hole  52  and the port hole  52  to move the sleeve  252  and a slider  150  rearward for cycling a mechanism  36  disposed in the receiver interior  34 . 
     In embodiments, the semiautomatic shotgun operates as follows. Cartridges of different power levels may be fired without adjusting of modifying the shotgun. Shotshells are loaded conventionally in the magazine. A shell is chambered by retracting the breech block. Upon firing the shell in the chamber explosive gases pass through the two ports in the barrel into the gas block assembly. A pair of passageway extends to the pair of valve chambers and then to the piston chamber. The passage ways to the piston chamber are selected to be a suitable size to restrict the passage of the gas that is to cause a pressure drop. If the pressure in the valve chambers is above a certain predetermined level, the relief valves open to lower the pressure lever. The valves open by the valve members lifting off of their respective valve seats. The pressure level transferred to the piston is then suitable for reliable and long-lasting operation of the recycling mechanism. 
     In embodiments the piston and piston chamber may be differently configured and still have the advantageous dual regulator arrangement. For example the piston could be cylindrical and engage a tubular cylinder forward of the ammunition chamber or above the ammunition chamber. 
     In one or more embodiments, the semiautomatic firearm  10  includes a spring  66  that is disposed inside a space defined by the magazine tube. In one or more embodiments, the semiautomatic firearm  10  includes a flange part  62 . 
       FIG. 20A  is a perspective view showing an assembly including a stock rod  64  and a spring loaded plunger assembly  50 . The spring loaded plunger assembly  50  includes a plunger  52  and a plunger housing  54 . In one or more embodiments, the plunger housing  54  has a male thread and a female thread. The male thread of the plunger housing  54  may threadingly engage a threaded hole in the receiver of a firearm. The female thread of the plunger housing  54  may threadingly engage one end of the stock rod  64 . The stock rod  64  may extend into the buttstock of a firearm. 
       FIG. 20B  is a side view showing an assembly comprising a spring loaded plunger assembly  50  including a plunger  52  and a plunger housing  54 . A male thread of the plunger housing is visible in  FIG. 20B . The male thread of the plunger housing  54  may threadingly engage a threaded hole in the receiver of a firearm. The assembly of  FIG. 20B  also incudes a stock rod  64  may extend into the buttstock of a firearm. The female thread of the plunger housing  54  may threadingly engage one end of the stock rod  64 . 
       FIG. 20C  is a cross-sectional view further illustrating the stock rod  64  and the spring loaded plunger assembly  50  shown in  FIG. 20A  and  FIG. 20B . The spring loaded plunger assembly  50  includes a plunger  52 , a plunger housing  54 , and an elastic element  56 . In the embodiment of  FIG. 20C , the elastic element  56  comprises a plurality of Belleville washers  60  arranged to form a stack  58 . 
       FIG. 20D  is an enlarged cross-sectional view further illustrating the spring loaded plunger assembly  50  shown in  FIG. 20C . With reference to  FIG. 20D , it will be appreciated that the Belleville washers  60  in the stack  58  are disposed in a series arrangement. In the example embodiment of  FIG. 20D , the orientation of adjacent Belleville washers  60  alternates. A portion of plunger  52  can be seen extending into a lumen defined by the stock rod  64  in  FIG. 20D . 
       FIG. 20E  is an exploded view further illustrating the stock rod  64  and the spring loaded plunger assembly  50  shown in  FIG. 20A  through  FIG. 20D . The spring loaded plunger assembly  50  includes a plunger  52  and an elastic element  56  that may be received in a plunger housing  54 . In the embodiment of  FIG. 20E , the elastic element  56  comprises a plurality of Belleville washers  60  arranged to form a stack  58 . A portion of plunger  52  may be inserted into a lumen defined by the stock rod  64  in the embodiment of  FIG. 20E . One end of the stock rod  64  may threadingly engage a female thread of the plunger housing  54 . 
       FIG. 20F  is a cross-sectional view further illustrating the stock rod  64  and the spring loaded plunger assembly  50  in accordance with an additional embodiment. The spring loaded plunger assembly  50  includes a plunger  52 , a plunger housing  54 , and an elastic element  56 . In the embodiment of  FIG. 20F , the elastic element  56  comprises a first coil spring  82  and a second coil spring  84 . 
       FIG. 20G  is an enlarged cross-sectional view further illustrating the spring loaded plunger assembly  50  shown in  FIG. 20F . With reference to  FIG. 20G , it will be appreciated that the second coil spring  84  is disposed inside a spring lumen  60  defined by the first coil spring  82 . One end of the stock rod  64  may threadingly engage a female thread of the plunger housing  54 . 
     Referring, for example, to  FIGS. 4 and 5 , an upward direction Z and a downward or lower direction −Z are illustrated using arrows labeled “Z” and “−Z,” respectively. A forward direction Y and a rearward direction −Y are illustrated using arrows labeled “Y” and “−Y,” respectively. “Forward” is the shooting direction of the shotgun. A starboard direction X and a port direction −X are illustrated using arrows labeled “X” and “−X,” respectively. The directions illustrated using these arrows are applicable to the apparatus shown and discussed throughout this application. The port direction may also be referred to as the portward direction. In one or more embodiments, the upward direction is generally opposite the downward direction. In one or more embodiments, the upward direction and the downward direction are both generally orthogonal to an XY plane defined by the forward direction and the starboard direction. In one or more embodiments, the forward direction is generally opposite the rearward direction. In one or more embodiments, the forward direction and the rearward direction are both generally orthogonal to a ZY plane defined by the upward direction and the starboard direction. In one or more embodiments, the starboard direction is generally opposite the port direction. In one or more embodiments, starboard direction and the port direction are both generally orthogonal to a ZX plane defined by the upward direction and the forward direction. Various direction-indicating terms are used herein as a convenient way to discuss the objects shown in the figures. It will be appreciated that many direction indicating terms are related to the instant orientation of the object being described. It will also be appreciated that the objects described herein may assume various orientations without deviating from the spirit and scope of this detailed description. Accordingly, direction-indicating terms such as “upwardly,” “downwardly,” “forwardly,” “backwardly,” “portwardly,” and “starboardly,” should not be interpreted to limit the scope of the invention recited in the attached claims. 
     The following United States patents are hereby incorporated by reference herein: U.S. Pat. Nos. 4,601,122, 4,702,146, 4,856,217, 4,872,392, 4,901,623, 5,429,034, 5,867,928, 5,872,323, 5,918,401, 5,959,234, 6,347,569, 6,382,073, 6,470,614, 6,508,160, 6,564,691, 6,619,592, 7,467,581, 7,775,149, 7,946,214, 7,963,061, 8,056,280, 8,065,949, 8,079,168, 8,109,194, 8,230,632, 8,245,625, 8,250,964, 8,312,656, 8,443,712, 8,528,458, 8,850,731, 8,939,060, 9,097,475, 9,212,856, and 9,383,149. 
     The above references in all sections of this application are herein incorporated by references in their entirety for all purposes. Components illustrated in such patents may be utilized with embodiments herein. Incorporation by reference is discussed, for example, in MPEP section 2163.07(B). 
     All of the features disclosed in this specification (including the references incorporated by reference, including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. 
     Each feature disclosed in this specification (including references incorporated by reference, any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. 
     The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any incorporated by reference references, any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed The above references in all sections of this application are herein incorporated by references in their entirety for all purposes. 
     Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement calculated to achieve the same purpose could be substituted for the specific examples shown. This application is intended to cover adaptations or variations of the present subject matter. Therefore, it is intended that the invention be defined by the attached claims and their legal equivalents, as well as the following illustrative aspects. The above described aspects embodiments of the invention are merely descriptive of its principles and are not to be considered limiting. Further modifications of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention.