Abstract:
A modular firearm is disclosed. The firearm that can be configured to operate using ammunition of different calibers via interchangeability of only a few parts. The firearm includes a foldable butt stock assembly for quickly and easily converting the firearm from an extended operating configuration to a compact transport configuration, and vice-versa. Additionally, the firearm includes a modular hand guard assembly having multiple mounting platforms for accommodating a variety of different accessories.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present Patent Application is a continuation application of previously filed co-pending Divisional application Ser. No. 13/037,459, filed Dec. 27, 2011, which application is a divisional application of previously filed U.S. patent application Ser. No. 12/640,531, filed Dec. 17, 2009, which application claims benefit of U.S. Provisional Patent Application Ser. No. 61/184,630, filed Jun. 5, 2009 according to the statutes and rules governing provisional patent applications, particularly 35 U.S.C. §119(a)(i) and 37 C.F.R. §1.78(a)(4) and (a)(5). The specifications and drawings of each of said applications referenced above are specifically incorporated herein by reference as if set forth in their entireties. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure relates to a modular firearm. 
       BACKGROUND OF THE INVENTION 
       [0003]    Typically, most conventional firearms have been adapted for specific tasks and generally are limited to use with specific calibers and/or types of ammunition. However, demand is increasing for firearms that can be modified to fire different types of ammunition, and/or can be reconfigured for different environments and uses. For example, in military applications today, the environments in which soldiers are forced to fight are changing such that they can be in open desert and then move into close quarter&#39;s battle in a more urban area within the matter of a few hours. At the same time, their weapons needs can further change, i.e., they might be faced with need for a longer range, sniping weapon or alternatively with needs for a more standard infantry rifle depending on the environment or situation. Carrying multiple different firearms is, however, impractical as adding undue weight and bulk to soldiers&#39; packs and gear. Additionally, for more specialized uses, such as for sniping and other tactical situations, the weapon must be configurable as needed to fit the shooter&#39;s particular needs and/or use in a particular combat situation. 
         [0004]    It therefore can be seen that a need exists for a modular firearm that addresses the foregoing and other related and unrelated problems in the art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0005]    The present disclosure generally is related to a modular firearm that is easily reconfigurable based on operational needs. More specifically, the disclosure relates to a modular firearm that is configurable to enable operation using ammunition of different or varying calibers via interchangeability of minimal parts, accommodates a variety of different accessories, is easily convertible from an operating condition to a compact and secure transport configuration, and can be configured with various accessories and stock arrangements as needed to meet a specific combat or tactical situation and/or the preferences of the user/shooter. 
         [0006]    According to another embodiment, the modular firearm can comprise a folding butt stock assembly that is moveable between an extended position for placing the firearm in an operating configuration and a folded position for placing the firearm in a transport configuration. The butt stock assembly includes a latch mechanism including a latch arm operable to remove a detent element from engagement with a chassis of the firearm, thereby enabling the stock to be unlocked from the extended position and pivoted into its folded position. In the folded position, the latch arm lockingly engages the chassis of the firearm, thereby securing the butt stock in the folded position. According to a further embodiment, the butt stock assembly can include a bolt handle opening configured to receive and retain a portion of the bolt assembly, such as, a projection, tab, or a bolt handle of the bolt assembly of the firearm when the butt stock is in the folded position, thereby helping to secure the bolt during transport of the firearm. 
         [0007]    According to a further embodiment, the modular firearm can additionally comprise a modular hand guard assembly for mounting accessories on the firearm. The hand guard assembly includes a hand guard having a plurality of rail mounting platforms, with each platform being disposed in a separate plane, including a top rail for mounting accessories on a top platform of the hand guard, and which attaches the hand guard assembly to a top portion of the receiver, and one or more rail sections attached about different planes of the hand guard and firearm for mounting accessories on the firearm. A bottom portion of the hand guard assembly can also be attached to a chassis of the firearm, with the hand guard assembly generally being free from direct attachment to a barrel of the firearm. One or more recoil-absorbing mounting lugs further may be integrated in each rail or rail section. 
         [0008]    According to still another embodiment, the modular firearm can include an integrated wire management system including one or more wire channels formed in an exterior surface of a chassis of the firearm and/or in an exterior surface of a hand guard of the firearm for accommodating cabling for one or more firearm accessories. Clips may be inserted in the channel(s) to secure the cabling and/or accessories at various locations along the channel(s). 
         [0009]    According to yet another embodiment, the modular firearm further may include an actuator for a bolt stop/guide mechanism. The actuator may be centrally located on an upper rear surface of the receiver to enable ease of actuation or engagement by right and left-handed users. 
         [0010]    Those skilled in the art will appreciate the above features and advantages, as well as additional features and advantages upon reading the following detailed description with reference to the accompanying drawings and appendix. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side view showing one embodiment of a modular firearm, according to one example embodiment; 
           [0012]      FIG. 2  is a partial cross-sectional view of the firearm; 
           [0013]      FIG. 3  is a perspective view of a barrel assembly of the firearm; 
           [0014]      FIG. 4  is an exploded view of a bolt assembly of the firearm; 
           [0015]      FIG. 5  shows an interchangeable bolt head of the bolt assembly, according to an embodiment, for use with the modular firearm of the present invention; 
           [0016]      FIG. 6  is a perspective view of the firearm illustrating operation of the bolt assembly of  FIG. 5 ; 
           [0017]      FIGS. 7-8  show an embodiment of a modular ammunition magazine for use with the modular firearm of the present invention; 
           [0018]      FIGS. 9 and 10  show an ammunition magazine conversion block, according to one example embodiment; 
           [0019]      FIGS. 11A-11C  are partially transparent views showing a butt stock assembly for the modular firearm, according to one example embodiment, and illustrate a process for folding the butt stock assembly from an extended position for operating the firearm to folded position for transporting the firearm; 
           [0020]      FIG. 12  is a perspective view of the butt stock in a folded position; 
           [0021]      FIG. 13  is a side view showing a modular hand guard assembly and cable management system for use with the modular firearm, according to an embodiment; 
           [0022]      FIG. 14  is a perspective view of a hand guard of the hand guard assembly; 
           [0023]      FIG. 15  is a bottom perspective view showing the connection of the hand guard assembly to a receiver of the modular firearm; and 
           [0024]      FIG. 16  shows a retaining clip of the cable management system. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]      FIGS. 1-16  show various features and components of a modular firearm F according to at least one example embodiment of the invention. In particular, the modular firearm F is shown as a bolt-action rifle, and more specifically, a bolt-action sniper rifle. However, it will be understood by those skilled in the art that the various aspects of the invention as described herein are suitable for other types of firearms, including various types of semi-automatic and fully automatic firearms such as handguns, rifles, shotguns, and other long-barreled firearms. 
         [0026]    As shown in  FIG. 1 , the modular firearm F generally includes a frame or chassis  10  including a receiver  20 , an interchangeable barrel assembly  100  mounted to the receiver  20  at a front end  12  of the chassis  10  and defining a chamber  30  at a position where the barrel  4  assembly  100  connects to the receiver  20 , a magazine well  40  defined in the chassis  10  and in communication with the chamber  30 , and a foldable butt stock assembly  400  mounted to a rear end  14  of the chassis  10 . A pistol-style handgrip  50  can be connected to the chassis  10  adjacent the rear end  14  of the chassis  10 , and a modular hand guard assembly  500  can be located along the front portion of the chassis  10  to assist in gripping and holding the firearm F. An interchangeable bolt assembly  200  generally is slidably received in the receiver  20  for operation of the firearm F. A fire control  60  is mounted to the chassis  10  for controlling firing of the firearm F. Additionally, ammunition magazine  300  will be received in the magazine well  40  for supplying ammunition to the receiver  20 . 
         [0027]    Still referring to  FIG. 1 , the receiver  20  generally will be constructed of a high strength, durable, but lightweight material, typically a metal or metal alloy such as a titanium alloy. Referring to  FIG. 2 , a barrel engagement portion  22  of the receiver  20  can be constructed of the same material as the remainder of the receiver  20 , or the barrel engagement portion  22  can be constructed of a different, durable, high strength material. For example, the barrel engagement portion  22  can be constructed of steel, thereby providing a steel-on-steel lockup arrangement between the barrel engagement portion of the receiver and the barrel extension  120  ( FIGS. 2 and 3 ) when the barrel extension  120  is also constructed of steel. As shown in  FIGS. 1 and 2 , the receiver  20  includes a breech  24  through which casings from spent ammunition cartridges may be ejected from the firearm F. 
         [0028]    Referring to  FIGS. 1 and 2 , the fire control  60  is provided for actuating/firing the firearm F and includes a trigger  62  as part of a trigger assembly housed in the chassis  10 . The fire control  60  is operably connected to the firing pin  260  such that actuation of the trigger  62  operates a firing pin  262  ( FIG. 2 ) to fire the firearm F. The fire control  60  can include an adjustable fire control system such as a Remington Arms Company, Inc. X Mark Pro fire control system, which generally is adjustable to enable variable pressure/trigger pulls, for example, from about 2.4 to about 4.5 pounds of pressure for actuation of the trigger assembly, although more or even less pressure also can be used as understood in the art. 
         [0029]    As shown in  FIG. 3 , the barrel assembly  100  includes a barrel  110  and a barrel extension  120  for mounting the barrel  110  to the receiver  20 . The barrel  110  and barrel extension  120  define a central axial bore  102  and can be integrally formed so as to define a substantially unitary, single piece barrel assembly, or can be separately formed and adapted to connect together as a multi-piece barrel assembly. The forward or distal end  122  of the barrel extension  120  can be attached to a rear end  114  of the barrel by a threaded connection or adhesive bond, for example. A rear end  124  of the barrel extension  120  can be attached to the barrel engagement portion  22  of the receiver  20  at the front end  12  of the chassis  10  in a known manner. A locking aperture  126  for interfacing with the bolt assembly  200  is formed at the rear end  124  of the barrel extension  120  in alignment with the central axial bore  102 . The locking aperture  126  includes a central aperture or bore  127  that communicates with the bore  102  of the barrel, and a plurality of recess portions  128  projecting radially outwardly from and spaced about the central aperture or bore  127  of the barrel. 
         [0030]    Referring to  FIGS. 2 ,  4  and  5 , the bolt assembly  200  of the firearm F generally includes a substantially hollow bolt body  210 , an interchangeable bolt head  230  that can be configured to fit ammunition cartridges of a specific caliber, a bolt plug  250 , and a firing pin assembly  160 . The bolt body  210  typically includes a bolt handle  214  that can be grasped for sliding the bolt body  210  within the receiver  20 , an axial bore  216  longitudinally extending from a rear or distal end  212  to a front or proximal end  211 , and a transverse locking bore  213  located adjacent the front end  212  of the bolt body as indicated in  FIG. 4 . The bolt body  210  further generally includes a bolt guide channel  217  formed in an exterior surface of the bolt body  210 . The bolt guide channel  217  includes a transversely extending channel segment  218  located near the rear end  212  of the bolt body  210 , and an axially extending channel segment  219  extending from the transversely extending segment  218  towards the front end  211  of the bolt body  210 . The bolt guide channel is adapted to be engaged by a guide member or rail within the receiver for guiding the bolt assembly during a loading and cocking operation of the firearm. 
         [0031]    As illustrated in  FIGS. 4 and 5 , the bolt head  230  includes a front or proximal end  231  configured to engage an ammunition cartridge as shown in  FIG. 2 , a rear or distal end  232  configured to be received in and attached to the bolt body  210 , and radially projecting locking lugs  234  ( FIG. 5 ) located along the side wall of the bolt body adjacent the front end  231 . The locking lugs  234  are configured to selectively engage the locking aperture  126  ( FIG. 2 ) of the barrel extension  120  for securing the bolt head  230  in place during firing of the firearm F, as will be described later. As shown in  FIGS. 4-5 , the bolt head  230  further includes an axially extending firing pin bore  235  that aligns with the tip portion  268  of the firing pin  262  of the firearm, a transverse bolt head locking bore  236 , an axially extending extractor mounting channel  237 , aligned transverse pivot pin bores  238  intersecting the extractor mounting channel  237 , an axially extending ejector mounting bore  239 , and a transverse ejector locking channel  240 . 
         [0032]    Referring again to  FIG. 4 , the bolt head  230  is releasably mountable to the front end  211  of the bolt body  210  by engagement of a locking pin  247  that is insertable in the transverse bolt head locking bores  213 ,  236  to enable removal and/or change-out of the bolt face as needed to change the caliber of the firearm and enable firing of different types/calibers of ammunition. The locking pin  247  further can be configured so as to include an axial bore  248  for receiving a tip portion  268  of a firing pin  262  therethrough so as to enable the bolt face change-out without interfering with or requiring change-out of the firing pin as well. 
         [0033]    Referring to  FIG. 5 , one or more extractors  241  can be pivotally mounted in one or more extractor mounting channels  237  (only one shown) by engagement with a pivot pin  243  inserted through the transverse pivot pin bores  238 . A biasing spring  242  can be inserted in the extractor mounting channel  237  between the bolt head  230  and the extractor  241  to pivotally bias the extractor  241  toward an engaging position for engaging and holding the ammunition cartridge for extraction upon operation of the bolt assembly after firing. As further indicated in  FIG. 5 , an ejector  244  can be mounted in the ejector mounting bore  239  with a locking pin  245  inserted through an ejector locking channel  240  for releasably securing the ejector. An ejector spring  246  generally coaxially positioned with the ejector  244  along the ejector mounting bore  239 , so as to bias the ejector forwardly and control axial movement during extraction and ejection of the spent cartridge by the ejector  244  of the bolt head. 
         [0034]    As illustrated in  FIG. 4 , the bolt plug  250  is generally hollow so as to define an axial bore  256  therethrough, and includes a front portion  252  insertable in the rear end  212  of the bolt body  210 , a rear portion  254 , and an axial bore  256  extending from the front portion  252  to the rear portion  254  for receiving the firing pin assembly  260 . The rear portion  254  of the bolt plug  250  is configured to abut the rear end  212  of the bolt body  210  and thereby limit the depth of insertion of the front portion  252  in the bolt body  210 . 
         [0035]    Sill referring to  FIG. 4 , the firing pin assembly  260  includes the firing pin  262 , which includes a head portion  264  mountable within the axial bore  256  of the bolt plug  250 , a body portion  266  insertable in the axial bore and mountable to the head portion  264 , and a tip portion  268 , which projects forwardly from the body portion  264  so as to extend through the bore  235  of the bolt head assembly for engaging and firing a round of ammunition or cartridge within the chamber of the firearm. The firing pin assembly  260  further generally includes a recoil spring  269  mountable around the body portion  266 . 
         [0036]    When the bolt assembly  200  is assembled as shown in  FIG. 2 , the bolt head  230  is connected to the front end  211  of the bolt body  210 , the firing pin assembly  260  is connected to the bolt plug  250 , and the bolt plug  250  and firing pin assembly  260  are inserted into the bolt body  210 . Specifically, the rear end  212  of the bolt head  210  is inserted into the axial hole  216  in the bolt body  210  through the front end  211  of the bolt body  102 , and the transverse locking bore  236  in the bolt head  230  is aligned with the transverse locking bores  213  in the bolt body  210 , and the locking pin  247  is inserted through the locking bores  213 ,  236 , thereby securing the bolt head  230  to the bolt body  210 . The firing pin assembly  260  is mounted to the bolt plug  250  such that the firing pin  262  is inserted through the axial bore  256  of the bolt plug  250 , the head portion  264  of the firing pin is attached to the bolt plug  250 , the body and tip portions  266 ,  268  of the firing pin extend from the front portion  252  of the bolt plug  250 , and the recoil spring  269  is positioned around the body portion  266  of the firing pin. The body and tip portions  266 ,  268  of the firing pin  262  and the front portion  252  of the bolt plug  250  are inserted into the bolt body  210  such that the tip portion  268  of the firing pin  262  is aligned with and can be actuated to extend through the axial firing pin bore  235  and the axial bore  248  in the locking pin  247 . The rear portion  254  of the bolt plug  250  further typically is secured to the rear end  212  of the bolt body  210  to complete the bolt assembly  200 . 
         [0037]    According to one example embodiment, the length of the bolt assembly  200  can allow feeding and ejection of various length ammunition cartridges up to 4.2″ long, although various other larger or smaller size and/or caliber cartridges also can be used. If it is desired to change the caliber of ammunition used with the firearm F, the bolt assembly  200  can easily be removed from the firearm F, and the bolt head  230  can be disconnected from the bolt assembly  200  by removing the locking pin  247  from the transverse locking bores  213  and  236 . With the locking pin removed, the bolt head  230  can be disengaged from the bolt body  102 . The bolt head  230  can then be replaced in the bolt assembly  200  with a replacement bolt head of the desired ammunition caliber, and the bolt assembly including the replacement bolt head can be reinstalled in the firearm F. Additionally, the barrel  110  ( FIG. 3 ), which defines a chamber of a first ammunition caliber, also generally will be disengaged from the receiver of the firearm and a new, second barrel defining a chamber configured to receive ammunition cartridges of a second, different caliber or size can be installed in its place to facilitate firing of a new, different caliber or type of ammunition. Together with various size ammunition magazines, or a reconfigurable magazine as noted below, the interchangeable barrel and bolt assembly can define a simple and different caliber conversion system or assembly for the firearm. 
         [0038]    As shown in  FIGS. 2 and 6 , when the firearm F is in a normal operational condition for firing a round of ammunition, the bolt assembly  200  is slidably mounted in the receiver  20  for chambering and ejecting ammunition. A bolt stop lever  80  is pivotally mounted to the receiver  20 . The bolt stop lever  80  is located at a central, upper, rear region of the receiver  20 , and includes an external grip portion  82  and a guide arm  84  extending from the grip portion  82 . The grip portion  82  is exposed on the external surface of the firearm F at the central, upper, rear region of the receiver  20 , and is operable by a user&#39;s finger or thumb at the exterior of the firearm F to pivot the bolt stop lever  80  in directions U 1 , U 2 . The guide arm  84  selectively registers with the guide channel  217  ( FIG. 4 ) extending along the bolt body  210  based on the pivotal position of the bolt stop lever  80 . The bolt stop lever  80  may be biased in the direction U 2  by a biasing member, such as a spring  86 , to protect against accidental disengagement of the bolt stop lever with the guide channel  217 . As  FIG. 2  indicates, the bolt stop lever cooperates with a transverse channel segment  218  of the channel  217  ( FIG. 4 ) in the bolt body  210  to guide forward and rearward linear movement of the bolt assembly  200  in the directions L 1 , L 2 , guide rotation of the bolt assembly  200  about its central axis in the directions T 1 , T 2  and selectively stop or limit travel of the bolt assembly  200  in the rearward direction L 2 . Thus, the channel  217  and the lever  80  together form a bolt stop and guide mechanism. As  FIG. 2  indicates, the engagement of the lugs  234  with locking aperture  126  helps to limit rearward linear movement of the bolt assembly  200  in the direction L 2 , so as to assist in selectively stopping or limiting travel of the bolt assembly  200  in the rearward direction L 2 . 
         [0039]    In operation of the bolt assembly  200  and the bolt stop lever, as shown in  FIGS. 2 and 6 , the bolt assembly  200  generally is disposed in a forwardmost, position in the receiver and rotated in the direction T 1  about its central axis with the bolt handle  104  turned to and its downwardmost position, when in an operating condition. The bolt head  230  extends through the locking aperture  126  in the barrel extension  120  and is oriented such that the locking lugs  234  are out of alignment with the outer aperture portions  129  of the locking aperture  126 , thereby locking the bolt head  230  in the barrel extension  120 . The bolt stop lever  80  is in its downwardmost position in the direction U 1  such that the guide arm  84  is in registry with the transverse channel segment  218  of the channel  217  in the bolt body  210 . With the bolt assembly  200  and the bolt stop lever  80  in this configuration, the bolt assembly  200  is restricted from moving in the directions L 1 , L 2  and the firearm F is configured for firing a round of ammunition C 1  from the chamber  30 . 
         [0040]    In order to eject a round of ammunition C 1  ( FIG. 2 ) or a casing of a spent round of ammunition C 1  from the magazine well  40  into the receiver  20 , the bolt assembly  200  can be rotated in the upward in the direction U 2  and moved rearward in the direction L 2 . Specifically, the bolt assembly  200  can be rotated in the upward in the direction U 2  such that the guide arm  84  is in registry with the axial channel segment  219  and the bolt handle  214  is in its upwardmost position. With the bolt assembly  200  in this position, the locking lugs  234  of the bolt head  230  are aligned with the outer aperture portions  129  of the locking aperture  126 . After rotating the bolt assembly  200  in the direction U 2  as described, the bolt assembly  200  can be moved rearwardly in the direction L 2  to its rearwardmost position such that the bolt head  230  passes out of the locking aperture  126 . 
         [0041]    During rearward movement of the bolt assembly  200 , the extractor  241  ( FIG. 5 ) will grab the casing/ammunition round C 1  and the ejector  244  will eject the casing/ammunition round C 1  from the breech  24  ( FIG. 2 ). The bolt assembly  200  is restricted from rotating during its rearward movement. When the bolt assembly  200  is in its rearwardmost position, the guide arm  84  remains in registry with the channel segment  219 , engaging a front edge of the channel segment  219  to prevent the bolt assembly  200  from being inadvertently removed from the receiver  200 . If it is desired to remove the bolt assembly  300  from the receiver (to replace the bolt head  110 , for example), the bolt stop  80  may be pivoted downward in the direction U 1  to deregister the guide arm  84  and disengage the locking lugs from the locking aperture, thereby allowing the bolt assembly  200  to slide rearwardly out of the receiver  20 . 
         [0042]    As indicated in  FIGS. 2 and 6 , after ejecting a spent cartridge or round, the bolt assembly  200  may be moved forward in the direction LI from its rearwardmost position in order to advance a next or new ammunition cartridge C 1  from the ammunition magazine  300  to the chamber. During such forward movement, the guide channel segment  119  engages the guide arm  84  such that the bolt assembly  200  cannot rotate in the directions T 1 , T 2  until the bolt assembly reaches its forwardmost position in the receiver. The bolt assembly  200  then can be turned downwardly in the direction T 1  to lock the bolt assembly  200  in position for firing the round of ammunition C 1 , as described above. 
         [0043]    As perhaps best shown in  FIG. 6 , the location of the bolt stop lever  80  enables ambidextrous operation of the bolt stop lever  80 . Additionally, with the bolt stop lever  80  positioned centrally on an upper rear surface of the receiver  20 , the bolt stop lever  80  is naturally shielded by a top rail  540  (described in detail later) and potentially by a scope or other aiming optics (not shown) or accessories that may be mounted on the top rail  540 . Inadvertent operation of the bolt stop/guide lever  80  can therefore be prevented without the requirement of additional fencing material or a cover. 
         [0044]    Referring to  FIGS. 2 ,  7  and  8 , a magazine  300  generally will be received within the magazine well  40 . In one embodiment, the magazine  300  can be a modular, interchangeable magazine including a magazine box or magazine body  302 , as shown in  FIGS. 7-8  and having a removable bottom plate  307 , and a magazine follower assembly  310  disposed in the magazine body  302  for advancing ammunition cartridges towards the top of the magazine body  302 . As indicated in  FIG. 7 , the bottom plate  307  of such a magazine can be removed from the magazine body  302  to enable repair or replacement/reconfiguration of parts by sliding the bottom plate forward in the direction L 1  off of the magazine body  302 . Conversely, the bottom plate  307  can be reconnected to the magazine body  302  by sliding the bottom plate rearwardly in the direction L 2  onto the magazine body  302 . 
         [0045]    As an example, the magazine  300  can be a center feed, double stack type magazine capable of feeding ammunition from 1-2 stacked, parallel rows or groups as indicated in FIGS.  2  and  7 - 8 . A spring-loaded magazine release button  304  ( FIGS. 6 and 9 ) can be provided on a rear wall  303  of the magazine body  302  for selectively locking the magazine  300  in the magazine well  40  and releasing the magazine  300  from the magazine well  40 . Specifically, when the magazine  300  is inserted in the magazine well  40 , the spring-loaded release button  304  is biased into engagement with a locking aperture  42 , which is positioned in a rear wall of the magazine well  40 , adjacent the receiver  20  and above a trigger guard  66  of the firearm F. The spring-loaded release button  304  can be depressed to disengage the locking aperture  42  and allow the magazine  300  to be removed from the magazine well  40 . 
         [0046]    In another embodiment, the magazine  300  can be adjustable so as to be reconfigurable to accommodate cartridges of different lengths, sizes, and/or different calibers of ammunition within a specific caliber by way of a removable/interchangeable spacer  320  that is insertable in the magazine body  302  at a front end  305  thereof. As illustrated in  FIGS. 7 and 8 , the magazine  300  generally can be configured to accommodate standard length ammunition cartridges C 1  when the spacer  320  is installed in the magazine body  302 . A cutout or channel  322  ( FIG. 8 ) is provided in the spacer  320  and is configured to receive and retain front ends of the cartridges C 1 . The spacer  320  is configured to extend substantially from a top  306  to the bottom plate  307  of the magazine body  302 . As perhaps best shown in  FIG. 7 , the spacer  320  can include resilient detent members  324  configured to lock the spacer  310  within the magazine body  302  by engaging locking channels  309  in side walls  308  of the magazine body  302 . The spacer  320  can be connected to the magazine body  302  by removing the bottom plate  307  and inserting the spacer upwardly into the magazine body in the direction H 1  until the detent members  324  lockingly engage the locking channels  309 . 
         [0047]    As indicated in  FIGS. 2 and 8 , the magazine  300  can be configured to accommodate longer, non-standard length ammunition cartridges C 2  when the spacer  320  is removed from the magazine body  302 . As  FIG. 8  illustrates, the spacer  320  can be removed from the magazine body  302  by depressing the detent members  324  until the detent members  324  disengage the locking channels  307 , and then moving the spacer  320  downward in the direction H 2 , out of the magazine body  302 . 
         [0048]    It is further envisioned that the spacer  320  can be interchanged with other spacers of different configurations to accommodate other ammunition cartridges of various lengths/sizes and/or calibers. Additionally, the magazine  300  may be interchanged with other magazines configured to accommodate ammunition cartridges of different calibers and/or lengths. For example, as shown in  FIGS. 9-10 , the receiver  20  can include a conversion block mounting bore  44  adjacent the magazine well  40  for mounting a magazine conversion block  350  in the magazine well  40 . The magazine conversion block  350  can be, for example, a 7.62 mm NATO conversion block that enables smaller 7.62 mm NATO ammunition magazines to be inserted in the magazine well  40 . Referencing  FIG. 10 , the magazine conversion block  350  includes a cradle portion  351  for receiving an ammunition magazine (not shown) that is smaller than the magazine  300  described above. As illustrated in  FIGS. 9 and 10 , the magazine conversion block  350  includes catch assembly  354  including a release arm  356  that is biased rearward in the direction L 2  by a pivotable biasing arm  358 . The biasing arm  358  is biased rearward against the release arm  356  by a torsional spring  359 . The magazine conversion block  350  also has a central mounting bore  360  configured for alignment with the conversion block mounting bore  44 . 
         [0049]    As can be understood from  FIGS. 9 and 10 , the magazine conversion block  350  can be installed in the magazine well  40  by sliding the conversion block  350  upward in the direction H 1  until the release arm of the magazine release button  304  ( FIG. 9 ) snaps into the locking aperture  42  above the trigger guard  66  and the central mounting bore  360  is aligned with the conversion block mounting bore  44 . A fastener  362 , such as a bolt or screw, can then be inserted into the bores  360 ,  44  to secure the magazine conversion block  350  in place. The magazine conversion block  350  can be uninstalled from the magazine well  40  by removing the fastener  362 , pressing the release arm  356  forward in the direction L 1  against the bias of the biasing arm  358  until the release arm  356  disengages the locking aperture  42 , and then sliding the magazine conversion block  350  downward in the direction H 2  out of the magazine well  40 . 
         [0050]    It can be understood from the above disclosure that, due to the reconfigurability of the barrel assembly  100  and the bolt assembly  200 , the firearm F can be modified to operate with ammunition of multiple calibers by changing or reconfiguring only the barrel  100 , bolt head  230 , and the magazine  300  if needed. According to one example, the barrel assembly  100 , bolt head  230  and magazine  300  may be packaged together as a caliber conversion assembly or kit configured for operation with ammunition of a specific caliber. Due to the modular designs of the barrel assembly  100 , the bolt assembly  200  and the magazine  300 , the barrel assembly  100 , bolt head  230  and magazine  300  can easily and quickly be installed in and uninstalled from the firearm F to replace and be replaced by respective barrel assemblies, bolt heads and magazines as needed for accommodating operation of the firearm with ammunition of other, different calibers and/or sizes. For example, the firearm F can be convertible to operate with ammunition calibers including, but not limited to, 338 Lapua Magnum and 300 Winchester Magnum. Furthermore, with the use of the magazine conversion block  350 , operation of the firearm F with 7.62 mm NATO ammunition is possible. It should be understood that, due to the modular design of the barrel assembly  100 , bolt assembly  200 , the firearm F also can be configured to be convertible to operate with ammunition calibers other than those specifically discussed. 
         [0051]      FIGS. 1 and 11A  show the firearm F in a shooting configuration with the foldable butt stock assembly  400  in an extended position, in line with the chassis  10 . As illustrated in FIGS.  1  and  11 A- 11 C, the butt stock assembly  400  includes a butt stock  410  having a body or frame  405 , and a hinge member  430  connected to a front end  411  of the butt stock  410 . The hinge member  430  is pivotally connected to hinge bracket  28  at the rear or distal end  14  of the chassis by a hinge pin  432 . A threaded member such as a screw  434  can extend transversely to and bear against the hinge pin or bolt  432  within the hinge member  430  to reduce slack or spacing in the connection between the hinge member  430  and the hinge bracket  28 , and further helps prevent the hinge pin  432  from separating from the chassis system. The axial position of the screw  434  in the directions L 1 -L 2  can be adjusted to vary the degree to which the screw  434  bears against the hinge pin  432 , and thereby adjust the amount of slack in the connection between the hinge member  430  and the hinge bracket  28 . The butt stock  410  includes a bolt handle window or opening  412  for receiving the bolt handle  214  when the stock is in the folded (or retracted) configuration ( FIGS. 11C-12 ). 
         [0052]    An adjustable butt plate  414  further generally is connected to a rear end of the stock body or frame  405 . The butt plate  414  can be vertically adjustable upwardly and downwardly in the directions H 1  and H 2  by an adjustment feature or member  422  adjacent a lower or bottom portion of the butt plate and pad  414 . The length of pull of the butt plate is adjustable, as indicated by arrows L 1 -L 2  in  FIG. 1 , by engagement/rotation of a first adjustment knob or wheel  416 . An adjustable cheek piece or comb  418 , typically formed from a resilient cushioning material, also can be connected to the stock body  405 , extending upwardly from the butt stock  410 , and is adjustable in a vertical direction with respect to the firearm F via a second adjustment knob or wheel  420 . As a result, the comb or cheek piece  418  can be adjusted in the direction of arrows H 1 -H 2  to fit a user&#39;s preference or comfort. The cheek piece further can be adjusted in the longitudinal direction (indicated by arrows L 1 -L 2 ) by disengaging fasteners securing the check piece, adjusting it forwardly or rearwardly as desired, and thereafter resecuring the cheek piece with the fasteners. Additionally the length of pull of the butt stock assembly  400  can be adjustable via the addition and removal of spacers that are insertable between the butt stock body  405  and the butt plate  414 . According to an exemplary embodiment, the length of pull may be adjustable between about 12.4 inches and about 14.4 inches. 
         [0053]      FIGS. 11A-11C  illustrate a latch mechanism  440  for the foldable butt stock assembly  400 , which is operable to selectively enable pivoting of the butt stock assembly  400  between an extended configuration ( FIGS. 1 and 11A ) and a folded configuration ( FIGS. 11C and 12 ). In the extended position, the butt stock assembly  400  extends rearwardly from the rear end  14  of the chassis  10 , in line with the chassis  10  ( FIGS. 1 and 11A ), enabling the firearm to be operated. In the folded configuration, the butt stock assembly  400  extends forwardly from the rear end  14  of the chassis  10 , substantially parallel to the chassis  10 , and is secured to a lateral side of the chassis  10 , thereby reducing the length of the firearm F to facilitate transporting the firearm. 
         [0054]    As shown in  FIGS. 11A-11B , the latch mechanism  440  generally includes a substantially L-shaped, pivotable latch arm  442  having a first arm portion  444  extending transversely to the longitudinal axis X of the firearm F/butt stock assembly  400 , a second arm portion  446  extending from the first arm portion  444  in a direction substantially perpendicular thereto along the axis X, and a pivot pin  448  provided at a junction of the first and second arm portions  444 ,  446 . A detent element or boss  450  is connected to a free end of the second arm portion  446  and extends substantially perpendicular thereto. The first arm portion  444  is partially housed within the hinge member  430  and has a free end protruding from a side of the hinge member  430  and terminating at a tab  445 . The second arm portion  446  extends within the hinge member  430 . The boss  450  is disposed within a transverse bore  452  in the hinge member  430  and is selectively received within a locking opening pocket  453  mounted to the hinge member  430  and positioned laterally opposite the hinge pin  432 . A biasing spring  454  located within the bore  452  biases the boss  450  in the lateral direction indicated by the arrow Z 1 . When the butt stock assembly  400  is in the extended position shown in  FIGS. 1 and 11A , the locking pocket  46  is aligned with the transverse bore  452  and the boss  450  is retained in a locking opening or pocket  453  under the biasing force of the spring  454 . Thus, the boss  450  locks the butt stock assembly  400  and the chassis  10  together such that the butt stock assembly  400  cannot be pivoted with respect to the chassis  10 . 
         [0055]      FIGS. 11B-12  illustrate a process for pivoting the butt stock assembly  400  from the extended configuration of  FIGS. 1 and 11A  to the folded configuration of  FIGS. 11C-12 . As shown in  FIG. 11A , the butt stock assembly  400  can be unlocked from the chassis  10  by moving the tab  445  in the rearward direction of the firearm as indicated by the arrow L 2  which causes the latch arm  442  to pivot clockwise about the pivot pin  448 , in the direction indicated by the arrow P 1 . As a result, the boss  450  is moved against the biasing force of the spring  454  in the lateral direction indicated by the arrow Z 2 , and is removed from the locking pocket  453 , thereby unlocking the butt stock assembly  400  from the chassis  10 . Thereafter, as shown in  FIGS. 11B-11C , the butt stock assembly  400  can be pivoted counterclockwise about the hinge pin  432 , in the direction indicated by the arrow P 2  at the hinge  432 . Once the butt stock  200  is pivoted in the direction P 2  to a point at which the boss  450  is out of alignment with the locking pocket  453 , the tab  445  may be released, causing the boss to be moved in the direction Z 1  under the biasing force of the spring  454 , and thereby causing the lever arm  442  to be pivoted counterclockwise in the direction P 2  under the biasing force of the spring  454 . The butt stock  400  then may be pivoted until the butt stock is positioned adjacent the chassis  10  and extends substantially parallel thereto ( FIG. 12 ). 
         [0056]    When the butt stock assembly  400  is positioned in this folded configuration or manner, the tab  445  lockingly engages a locking feature located on the sidewall of the chassis  10  adjacent the butt stock assembly  400 , shown in  FIG. 11C  as including, for example, a locking plate  70 , thereby securing the butt stock assembly  400  in the folded position. Specifically, the tab  445  lockingly engages an edge  73  of an opening  72  in the locking plate  70  or other, similar locking feature as will be understood by those skilled in the art. As shown in  FIGS. 11C and 12 , when the butt stock assembly  400  is secured in the folded position, the bolt handle  214  extends through and is retained within the bolt handle opening  412 , thereby preventing movement and operation of the bolt assembly  200 . Additionally, when the butt stock assembly  400  is in its folded position, the boss  450  protrudes from the firearm F through the transverse bore  452 , as indicated in  FIG. 12 . The tab  445  can be released from locking engagement with the edge  73  of the locking plate  70  by pressing the boss  450  against the biasing force of the spring  454  in the direction indicated by the arrow Z 2 , which causes the latch arm  442  to pivot clockwise in the as indicated by the arrow P 1 . Thereafter, the butt stock assembly  400  can be pivoted clockwise about the hinge pin  432  in the direction P 1  and the boss  450  can be released and allowed to move in the direction Z 1  under the biasing force of the spring  454 . The butt stock assembly  400  can then be pivoted in the direction P 1  until the butt stock assembly  400  is secured in its extended position, as described above with respect to  FIGS. 1 and 11A . 
         [0057]    As indicated in  FIGS. 11A-11B , the locking opening or pocket  453  retains the boss  450  until the force of the spring  454  is overcome by rotation of the butt stock assembly, and generally is aligned with the boss  450  when the stock is in its extended position. The position and/or alignment of the pocket  453  further can be adjusted as needed to accommodate changes in the butt stock assembly. As indicated in  FIGS. 11A-11C , a locking set screw or similar locking member  460  can be located just above the locking opening or pocket  453  to secure the position thereof with respect to the boss  450  when the butt stock assembly is in its extended position. When this set screw is loosened,  453  can be rotated and thereby taking the “slop” or variance out of the union between the lower stock assembly and the buttstock assembly. The receiving bore of the locking pocket  453  also is generally eccentrically shaped, and rotating the pocket, which thus rotates the receiving bore with respect to the boss  450 , tightens up the interaction between the receiving bore of the locking pocket  453  and the boss  450  to help ensure secure and constant engagement of the boss  450  within the receiving bore of the locking pocket  453  to lock the stock in its extended position. Once the desired adjustment of the locking pocket is made, the set screw  460  can be tightened to secure or fix the locking pocket  453  in place. 
         [0058]    FIGS.  1  and  13 - 15  show features of the hand guard assembly  500 . As shown in  FIGS. 13 and 14 , the hand guard assembly  500  includes a substantially tubular hand guard  510  defining a plurality of rail mounting platforms and a substantially tubular hand guard connector  530  for connecting the hand guard  510  to the front end  12  of the chassis  10 . According to the exemplary embodiment illustrated herein, the hand guard  510  defines eight rail mounting platforms including a top platform  512 , side platforms  514 ,  516 ,  518 , a bottom platform  520 , and side platforms  522 ,  524 ,  526 , with each platform being disposed in a separate plane. Accordingly, the hand guard  510  has an octagonal cross-sectional shape in a plane transverse to the longitudinal axis of the hand guard assembly  500 . Each platform  512 ,  514 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526  includes a plurality of longitudinally spaced vent holes or openings  502  for venting heat from the barrel  110 , and a plurality of longitudinally spaced mounting holes  504  for connecting accessory mounting rails  560 ,  580  to the hand guard  510 . In the embodiment shown, the vent holes  502  are substantially oval in shape, and are positioned along the length of the hand guard  510  in alternating arrangement with the mounting holes  504 . However, one skilled in the art will understand that other configurations of vent holes and mounting holes are possible. 
         [0059]    As shown in  FIGS. 13 and 15 , the hand guard connector  530  can be formed integrally with or connected to a rear end of the platforms  512 ,  314 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526 , and includes a flange  532  for connecting the hand guard  510  to the chassis  10 . The flange  532  is formed at a lower portion of the hand guard connector  530 , and the hand guard connector  532  can be connected to a lower portion of the front end  12  of the chassis  10  with fasteners, such as bolts or screws  534 , inserted through the flange  532 . 
         [0060]    As also shown in  FIGS. 13 and 15 , a top accessory mounting rail  540  for mounting accessories to the firearm F is provided on the top platform  512  (at the 12 o&#39;clock position) of the hand guard  510 . The top rail  540  can be adjustable and can be a replaceable Mil. Std. 1913 rail, for example. Referring to  FIG. 22 , the top rail  540  includes a top surface  544  for interfacing with an accessory (not shown) such as a scope or other optic device, a bottom surface  546  for interfacing with the top platform  512 . A plurality of mounting holes  548  extend through the top and bottom surfaces  544 ,  546  for mounting the top rail  540  to the top platform  512 . At least one recoil absorbing lug  549  extends from the bottom surface  546  of the top rail  540  at a rear section thereof. Each recoil absorbing lug  549  can be integrally formed with the bottom surface of the top rail  540  or with an associated platform of the hand guard assembly, or can be separately insertable into or engageable with the top rail and/or an associated platform. As shown in  FIG. 19 , the top rail  540  can be secured to the hand guard  510  by aligning mounting holes  548  with corresponding mounting holes  504  in the top platform  512  and corresponding mounting bores  90  (shown in  FIG. 2 ) in the receiver  20 , aligning each and inserting fasteners such as threaded fasteners  550  through aligned mounting holes  548 ,  504  and aligned mounting holes and bores  548 ,  90 . The recoil absorbing lug can engage a recess in the top of the receiver  20 , for seating the lug and helping secure the accessory mounting rail to the receiver. The rail  540  further can be a substantially continuous long rail so as to ensure that all optics and/or accessories mounted on the top rail are planarly aligned. 
         [0061]    Each of the remaining platforms  512 ,  514 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526  may have one or more accessory mounting rails, such accessory mounting rails  360 ,  380 , connected thereto for mounting accessories on the firearm F. The rails  360 ,  380  and any other mounting rails connected to the platforms  512 ,  314 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526  can also be Mil. Std. 1913 rail sections. The rails  360 ,  380  may be constructed to be shorter in length than the platforms as shown, or they may be constructed to extend substantially the entire length of the platforms  512 ,  514 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526 . 
         [0062]    Referring to  FIGS. 14 and 15 , the rails  560 ,  580  each include a top surface  564 ,  584  for interfacing with an accessory, a bottom surface  566 ,  580  for interfacing with one of the platforms  514 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526 , a plurality of mounting holes  568 ,  588 , and one or more recoil absorbing lugs  590  received within the Mounting holes  588  formed in the rail surfaces. The Mounting holes  568 ,  588  are configured to be aligned with corresponding mounting holes  504  in one of the platforms  514 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526 . The recoil absorbing lugs  569 ,  589  also can be formed integrally with the bottom surfaces  566 ,  586  or the rails or can be inserted into the rail and platform(s) of the hand guard assembly. The recoil absorbing lugs  569  of the rail  560  are spaced such that they are configured to engage a rear edge  502   a  and a front edge  502   b  of the same vent hole  502 . The recoil absorbing lugs  569  of the rail  560  are spaced such that they are configured to engage a rear edge  502   a  of one vent hole  502  and a front edge  502   b  of another vent hole  502 . 
         [0063]    Thus, a rail section  360  or  380  can be secured to the hand guard  510  by inserting the pair of lugs  569  or  589  in one or more vent holes, and/or by aligning each mounting hole  568  or  588  with a corresponding mounting hole  504 , and inserting fasteners such as threaded fasteners  570  through aligned mounting holes  568  and  504  or aligned mounting holes  588  and  504 . 
         [0064]    By way of example, a scope (not shown) or other optic can be attached to the top rail  540  and/or a bipod (not shown) can be attached to a bottom rail section  350 . However, because each platform  514 ,  516 ,  518 ,  520 ,  522 ,  524 ,  526  is positioned in its own plane and includes a plurality of mounting holes  502 , rails of different sizes and/or configurations can be mounted at various positions and in various configurations and numbers along the length of each platform, thereby enabling various types and combinations of accessories to be mounted on the hand guard  510 . Furthermore, it should be understood that the accessory mounting rails  560 ,  580  can be mounted on other surfaces of the firearm F, such as, but not limited to the butt stock  410  ( FIG. 1 ). 
         [0065]    Due to the manner in which the hand guard assembly  500  is connected to the chassis  10 /receiver  20 , the hand guard assembly  500  surrounds the barrel  110 , but is not directly connected to the barrel  110 . Because the hand guard assembly  500  is not directly connected to the barrel  110 , the hand guard  510  is substantially free-floating with respect to the barrel, thereby improving accuracy in operating the firearm F. The recoil absorbing lugs  549 ,  569 ,  589  absorb recoil forces generated by firing the firearm F and thereby resist shearing of accessories mounted on respective rails  540 ,  560 ,  580 . 
         [0066]    In addition, radially located sling swivel cups, such as indicated at  700  in  FIG. 13 , can be attached adjacent the fore-end and the butt stock of the firearm F. There typically can be four sling swivel cups, although more or fewer sling swivel cups also can be used. One to three of these sling swivel cups can be used to attach carrying slings to the weapon via a push-fit sling swivel. The chassis  10  and the buttstock body  400  also can include one or more of such sling swivel cups for attaching an opposite end of the carrying sling thereto. 
         [0067]    Certain electronic accessories, such as optics, which can be attached to the firearm F by mounting on the hand guard  510  or other parts of the firearm F, often require wire or cable connections in or on the firearm. Thus, as illustrated in  FIGS. 13 and 15 , the firearm F can include a wire management system  600  including one or more wire channels  602  integrated in exterior walls of the chassis  10 , the hand guard  510 , and/or the hand guard connector  530 . One or more wires or cables  604  can be placed in the channel(s)  600  and routed to components and/or accessories in and/or on the firearm F. The wire(s)  604  can be secured in the channel(s)  600  by retaining clips  610  inserted into openings  601  the channel(s)  600 . Each retaining clip  610  ( FIG. 16 ) can include a top  611  and a pair of deformable ribbed arms  612  defining a passage  614  therebetween sized to receive a wire  604 . The ribbed arms  612  can be configured to engage an opening  601  by a press-in fit. To secure a wire  604  ( FIG. 13 ) in a channel  602 , the wire  604  can be inserted through the passage  614  of one or more clips  610 , and the each clip  610  can be pressed into an opening  601  in the channel  602 . When a clip  610  is pressed into an opening  601 , the ribbed arms are deformed towards each other and, as a result, engage the wire  604  by an interference fit. 
         [0068]    The foregoing disclosure provides illustrative embodiments of the invention and is not intended to be limiting. It should be understood that modifications of the disclosed embodiments are possible within the spirit and scope of the invention, and the invention should be construed to encompass such modifications.