Patent Publication Number: US-2023160650-A1

Title: Method and Apparatus For Converting an AR-15 Firearm into a Bullpup Configuration

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is related to U.S. 63/281,967 filed on Nov. 22, 2021 titled Method and Apparatus for Converting an AR-15 Firearm into a Bullpup Configuration, which is incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to firearms and, more particularly, to an apparatus and method for converting an AR-15 rifle to a bullpup rifle configuration. The apparatus and method involve disassembling parts of the AR-15 firearm and coupling a kit of components, including a bullpup lower receiver and other components, to the disassembled AR-15. 
     A bullpup firearm rifle is a firearm with its action and magazine behind the trigger—the opposite of traditional rifle firearms. This configuration reduces the length of the firearm by about 25%, includes a more forward trigger, and is typically seen as being more maneuverable than a full-size rifle. A bullpup rifle may also have a shortened or removed butt stock. Many gun enthusiasts have a desire to have a bullpup firearm but find them hard to find to purchase. Alternatively, an existing rifle may be converted to a bullpup but may require complicated and extensive engineering to do so. However, enthusiasts of high-powered weapons may have an AR-15 and would find it desirable if the existing AR-15 could be easily modified into a bullpup configuration. 
     Therefore, it would be desirable to have a method and kit for disassembling portions of an AR-15 and assembling a bullpup firearm using parts of both the disassembled AR-15 and the bullpup kit. 
     SUMMARY OF THE INVENTION 
     Therefore, a method for disassembling and converting an AR-15 into the bullpup configuration of an AR-15 firearm assembly includes releasing and removing specific components of the AR-15 and then replacing the removed components with elements from the kit. Specifically, the standard buttstock of the AR-15 is removed and replaced with a bullpup buttstock. Further, the AR-15 bolt carrier group and buffer tube is removed and replaced with a bullpup bolt carrier group and buffer plug. Finally, the AR-15 trigger guard is removed and replaced with a trigger guard plate from the kit and which essentially covers the stock trigger which remains. 
     Then, additional elements of the bullpup assembly may be coupled to the modified AR-15 assembly. Specifically, the bullpup receiver (or sometimes called the lower receiver) is coupled to the barrel assembly of the modified AR-15 assembly, the bullpup lower receiver including a bullpup trigger portion. Then a trigger linkage is connected between the bullpup trigger portion and AR-15 stock trigger so that pulling the bullpup trigger simultaneously actuates the stock trigger to fire the firearm. The actual AR-15 trigger is hidden behind a pair of trigger guide plates and a side plate. The result is that the AR-15 is converted into a bullpup configuration. The method may be reversed without any damage or modification of the stock components of the unmodified AR-15 firearm. 
     Therefore, a general object of this invention is to provide a bullpup configuration of an AR-15 firearm assembly and a method for disassembling and converting an AR-15 into the bullpup configuration of an AR-15 firearm assembly. 
     Other objects and advantages of the present invention will become apparent from the following description taken in connection with the accompanying drawings, wherein is set forth by way of illustration and example, embodiments of this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of a bullpup assembly converted from an AR-15 firearm according to a kit and method of conversion according to a preferred embodiment of the present invention; 
         FIG.  2   a    is a side view of the bullpup assembly as in  FIG.  1   ; 
         FIG.  2   b    is a reverse view of the bullpup assembly as in  FIG.  2     a;    
         FIG.  3    is an exploded view of the bullpup assembly as in  FIG.  1   ; 
         FIG.  4   a    is a perspective view of a portion of the bullpup assembly taken from  FIG.  1   ; 
         FIG.  4   b    is an exploded view of the bullpup assembly as in  FIG.  4     a;    
         FIG.  5   a    is an exploded view of the bullpup assembly as in  FIG.  4     a;    
         FIG.  5   b    is a further exploded view of the bullpup assembly as in  FIG.  5     a;    
         FIG.  6   a    is another perspective view of the bullpup assembly as in  FIG.  1   ; 
         FIG.  6   b    is an isolated view on an enlarged scale taken from  FIG.  6     a;    
         FIG.  6   c    is an isolated view on an enlarged scale taken from  FIG.  6     a;    
         FIG.  7   a    is a perspective view of the bullpup assembly as in  FIG.  1    with selected cover plates removed for clarity; 
         FIG.  7   b    is an isolated view on an enlarged scale taken from  FIG.  7     a;    
         FIG.  7   c    is an isolated view on an enlarged scale taken from  FIG.  7     a;    
         FIG.  8   a    is another is a perspective view of the bullpup assembly as in  FIG.  1   ; 
         FIG.  8   b    is an isolated view on an enlarged scale taken from  FIG.  8     a;    
         FIG.  9    is a perspective view of a trigger linkage removed from the bullpup assembly as in  FIG.  1   ; 
         FIG.  10   a    is a perspective view of the bullpup assembly according to the present invention, illustrated removed from the lower receiver and with the bullpup bolt carrier group installed; 
         FIG.  10   b    is an isolated view on an enlarged scale taken from  FIG.  10     a;    
         FIG.  11    is an isolated view of the forward charging handle removed from the assembly for clarity; 
         FIG.  12   a    is an isolated perspective view of the bolt carrier group removed from the bullpup assembly of  FIG.  10     b;    
         FIG.  12   b    is an isolated view on an enlarged scale taken from  FIG.  12     a;    
         FIG.  12   c    is an isolated view on an enlarged scale taken from  FIG.  12     a.    
         FIG.  13   a    is a rear perspective view of the bull pup assembly as in  FIG.  1   ; 
         FIG.  13   b    is an isolated view on an enlarged scale taken from  FIG.  13   a   ; and 
         FIG.  14    is a perspective view of an unmodified AR-15 rifle. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A bullpup configuration of an AR-15 firearm assembly and a method for converting an AR-15 into the bullpup configuration of an AR-15 firearm assembly will now be described in detail with reference to  FIGS.  1  to  14    of the accompanying drawings. Accordingly, a bullpup kit  10  includes a bullpup buttstock  12 , a bullpup lower receiver  14 , a side plate  16 , a pair of trigger guard plates  18 ,  20  and a trigger linkage  30 , and a modified bolt carrier group  24 . 
     The bullpup configuration of a modified AR-15 is shown assembled in  FIG.  1    but will be first described according to a method for disassembling a standard configuration of an AR-15. It will be understood that several components of a standard AR-15 will remain after disassembly thereof for use with components of a bullpup kit  10  in order to form a fully assembled bullpup configuration of an AR-15. A standard unmodified AR-15 firearm is illustrated in  FIG.  14   . 
     In order to convert a standard configuration AR-15 to the bullpup configuration, certain components of the standard configuration AR-15 must be detached or uncoupled from the components that will remain and receive the components from the bullpup configuration. For instance, the standard AR-15 includes a buttstock  102  coupled to a rear end of an AR-15 body frame  40  (which is the lower receiver of the AR-15). The first step of the method of conversion is to uncouple the AR-15 buttstock  102  and to attach the AR-15 stock  12  in its place. It will be understood that components described may be coupled using pins, screws, or the like. Next, the standard AR-15 includes a trigger guard surrounding and protecting a standard AR-15 trigger  41  and this trigger guard or at least a bottom wall thereof is removed. This standard structure will be replaced by corresponding structures from the bullpup kit  10  as will be explained in greater detail later. 
     Further, it is desirable to remove the stock AR-15 bolt carrier group that fires and ejects bullets from the AR-15 and to replace it with a bolt carrier group  24  (or “BCG”) and buffer plug from the bullpup kit  10 . The bolt carrier group  24  may include a rear charging handle  25  that is operable to load a bullet casing into the chamber to be shot as is known in the art. In the stock AR-15, the bolt carrier group may include a rear charging handle  25  that may be alternately positioned to the rear or to the side of the bolt carrier group. However, the converted bullpup configuration will include a forward charging handle  25   a  that is positioned forward of the trigger, as will be described below and is shown in  FIG.  11   . 
     With the stock buttstock, stock trigger guard, and bolt carrier group removed, what is left will be referred to as a modified AR-15 assembly to which all elements of the bullpup kit  10  may be attached in replacement or in addition as described below. 
     The bullpup kit  10  includes a bullpup lower receiver  14  that provides the primary framework to which other components may be attached or that forms other components. More particularly, the bullpup receiver  14  includes an upper surface  15  (also referred to as the bullpup upper receiver) defining an elongate and generally planar surface that may be coupled to the body frame  40  (AR-15 lower receiver) of the modified AR-15 assembly. It is understood that the upper surface  15  may support a barrel assembly  42  of the modified AR-15 assembly and, more particularly, may include a silencer or sound suppressor coupled or positioned about the barrel. The bullpup receiver  14  may also be referred to as the lower receiver. 
     The bullpup receiver  14  may include a trigger handle  22  and bullpup trigger  21  ( FIG.  8   a   ). The trigger  21  may be protected from damage or accidental firing by a bullpup trigger guard  21   a.  In some embodiments, the bullpup handle  22  may have a pistol grip configuration that is ergonomic and easy to grip in a person&#39;s hand. Further, the bullpup kit  10  may include a trigger linkage  30  that operably connects the bullpup trigger  21  with the AR-15 trigger  41  in such a manner that when a user pulls the bullpup trigger  21 , the stock AR-15 trigger  41  is pulled simultaneously so as to fire the AR-15 ( FIGS.  7   a    to  9 ). More particularly, the bullpup linkage  30  may include a trigger link  31  having a proximal end  32  (also referred to as a link proximal end) coupled to the bullpup trigger  21 , an opposed distal end  33  (also referred to as a link distal end) and has a linear configuration. The bullpup linkage  30  may also include a trigger bar  34  having a proximal end  35  (also referred to as a bar proximal end) coupled to the distal end  33  of the trigger link  31  and have a distal end  36  (also referred to as a bar distal end) operatively coupled to the AR-15 trigger  41  ( FIG.  9   ). The trigger bar  34  may have an offset configuration. Even more particularly, the proximal end  32  of the trigger link  31  and the distal end  36  of the trigger bar  34  include connection pins  37 , respectively, that extend away horizontally from the trigger link  31  and trigger bar  34 , respectively, first for connecting the link and bar and to bear against the AR-15 trigger  41 , respectively ( FIG.  9   ). The connection pins  37  extend through slots  27  and  19 , respectively, of respective guide plates  26  and  18  ( FIGS.  4   b  and  5   b   ). 
     The bullpup kit  10  may include a bullpup guide plate  18  that may be attached to or integrally constructed with the bullpup trigger  21 , the bullpup guide plate  18  defining what will be referred to as a bullpup trigger slot  19  through which a respective connection pin  37  extends. The connection pin  37  moves in the bullpup trigger slot  19  when the bullpup trigger  21  is actuated which causes the trigger linkage  30  to move rearward — actuating the AR-15 trigger  41  to fire the firearm. The standard AR-15 includes a guide plate  44  that is coupled to the body frame  40  and positioned proximate the AR-15 trigger  41  and that defines what will be referred to as an AR-15 guide slot  45  ( FIG.  3   ). A respective connection pin  37  moves rearwardly in the AR-15 guide slot  45  and bears against the AR-15 trigger  41  when the trigger linkage  30  is actuated such that the AR-15 is fired. An auxiliary guide plate  26  may also be provided and which defines an auxiliary slot  27  configured to receive a connection pin  37  ( FIG.  5   a   ) for coupling the trigger link  31  and trigger bar  34  together ( FIG.  5   a   ). 
     The guide plate  18  and a trigger guard  20  essentially sandwich the AR-15 trigger  41  so as to shield it from damage and to prevent inadvertent actuation ( FIG.  5   a   ). In addition, the bullpup kit  10  may include a side plate  16  that may be coupled to the bullpup receiver  14  and is positioned to cover and protect the AR-15 trigger guide plate  44 . 
     Now described in more detail, the bolt carrier group (BCG)  24  included in the bullpup kit  10  and which replaces the traditional bolt carrier group of the original AR-15 assembly is critical to the proper and superior functionality of the converted assembly of the bullpup configuration. Specifically, the bolt carrier group  24  includes an elongate forward charging handle  25   a  forward of the bullpup trigger  21  ( FIG.  10   a   ), actuation of which simultaneously operates the rear charging handle  25  so as to push the bullpup bolt carrier group  24  rearwardly to load a bullet from a magazine  48  into the chamber to be fired. The charging handle assembly is configured to ride along the stock gas tube  57  of the barrel assembly  42  ( FIG.  10   a   ). 
     The bullpup carrier group  24  includes carrier portion  24   a  and a spring assembly  50  having a plurality of compression springs  51  each having a distal end  51   a  seated in a ring-shaped flange referred to as a buffer plug  51   c  associated with the body frame  40  and a proximal end  51   b  that interfaces with the carrier portion  21   a  that slidably recoils to compress the springs  51 , e.g., when a bullet is fired. The springs  51  are configured to compress toward the buffer plug  51   c  when the charging handle  25 /charging arm  23  is pulled back and then to push the carrier member  24   a  forwardly when the charging handle  25  is released (which releases the tension on the springs). It should be noted that the modified AR-15 is able to accommodate and absorb the recoil of the carrier portion  24   a  without the standard buffer that would conventionally extend into the buttstock. 
     Now, more particularly, the BCG  24  includes a plurality of guide rods  53  each extending longitudinally from buffer plug  51   c  forwardly in the direction of the carrier portion  24   a.  Each spring of said plurality of compression springs  51  are positioned loosely about the plurality of guide rods  53 , respectively. While each guide rod  53  has a fixed length, each spring  51  is configured to compress when loaded and to expand/decompress when the load is removed. Further, the carrier portion  24   a  of the BCM  24  includes a casing having an outer surface that defines a plurality of grooves  55  (which may also be referred to as channels  55 ), the plurality of grooves  55  being radially spaced apart in a predetermined and perfect alignment with the plurality of guide rods  53 . In operation, when the carrier portion  24   a  is moved rearwardly (such as when the charging arm  23  is pulled rearwardly), whether manually to talk the hammer  54  or when recoiling after firing a bullet, the plurality of guide rods  53  are configured to slide along the plurality of grooves  55 , respectively while the associated plurality of springs  51  are compressed. This relationship is best shown in  FIG.  10     b.    
     Operation of the bolt carrier group (BCG)  24  may be described in detail as follows. To initiate operation, the charging handle  25  must be pulled rearwardly towards the stock  12  of the gun in alignment with the barrel. On the top of the BCG  24  there is a shelf which interfaces with the charging arm  23 . Pulling the charging handle  25  rearwardly (using the forward  25   a  or rearward  25  handle), pulls the charging arm  23  rearwardly which pushes the carrier portion  24   a  rearwardly due to the interface between the charging arm  23  and carrier portion  24   a.  As the carrier portion  24   a  moves rearwardly, the coils of the buffer spring  51  are pulled into tension/compressed ( FIG.  12   a   ). The rearward motion of the carrier member  24   a  cocks the hammer  54  ( FIG.  10   b   ) of the trigger as the bottom of the carrier member  24   a  slides over the hammer  54 . (by which, via the bullpup trigger linkage, the bullpup trigger  21  is simultaneously cocked), Once the charging handle has been pulled to the rear to its full extent, the charging arm  23  is released. At this point the coiled energy (compressed energy) from the spring  50  projects the carrier portion  24   a  forward. On its forward motion, the bolt strips the top round from the magazine  48  and it is pushed into the chamber (directed via feed ramps). At this time a cartridge  11  carrying a bullet round is chambered, the hammer is cocked and the weapon is ready to fire by pulling the bullpup trigger  21 . Once the trigger has been pulled the hammer  54  strikes the firing pin, the firing pin striking the primer  49  of the cartridge  11  which ignites the powder in the cartridge  11 . Burning gases from the spent cartridge may exit the barrel through gas tube  57  and relief valve, part of which is visible in  FIG.  12   a    and operatively in communication with the barrel  43 , push the carrier portion  24   a  rearward and the entire cycle is repeated. 
     In another aspect and as shown in  FIGS.  13   a  and  13   b   , when the carrier member  24   a  is thrust rearward and then propelled forwardly as described above, a now empty cartridge  11  is ejected from the chamber and a new cartridge is loaded in preparation for the next shot. As is known by anyone who has fired virtually any type of firearm, a cartridge made jam inside the chamber, making the firearm and usable until the gyms cleared. To solve this problem, an interior surface of the chamber in the present invention defines a small depression  13  that is configured to receive a user&#39;s finger or tool in an action to loosen, pop out, or manually eject a jammed cartridge  11  ( FIG.  13   b   ). 
     Using the bullpup kit  10 , a conventional AR-15 firearm  100  may be converted to a bullpup configuration. Specifically, the AR-15 firearm  100  is, in part, disassembled and such that components from the bullpup kit  10  may then be mounted to the AR-15 frame  40  that remains as described above. The method may be selectively reversed to return to the conventional AR-15 firearm  100  configuration—all without making any permanent modifications to the components of either assembly. 
     It is understood that while certain forms of this invention have been illustrated and described, it is not limited thereto except insofar as such limitations are included in the following claims and allowable functional equivalents thereof.