Abstract:
Semi-automatic features can be eliminated from a weapon that originally had a bolt carrier that was reciprocated by a gas tube communicating with a barrel. After eliminating the gas tube, a carriage and pushing member can be taken from a kit and installed on the weapon. The carriage is reciprocatably mounted at the barrel forward of the bolt carrier, with the pushing member connecting between the carriage and the bolt carrier. The carriage can be manually reciprocated to reciprocate the push member and the bolt carrier.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to semi-automatic weapons and methods and kits for modifying the weapon so it will no longer operate semi-automatically and will require, after each firing, a manual operation to reload the weapon. 
     2. Description of Related Art 
     In a common semi-automatic rifle, a bolt carrier is slidably mounted inside an upper receiver that fits in a lower receiver that may have a trigger, pistol grip, and butt stock. A charging handle on the upper receiver can be used to retract the bolt carrier and load a live round before releasing the bolt carrier, allowing it to move forward into the firing position. Upon firing, exhaust gas tapped from the barrel is fed back through a gas tube to impinge upon a key on the bolt carrier to drive it backwardly. This motion automatically ejects the spent cartridge and then feeds another live around, before the bolt carrier returns to the firing position. 
     In a semi-automatic weapon the trigger must be pulled once each time a round is fired. In a fully automatic weapon such as a machine gun, the trigger is pulled once and multiple rounds of ammunition are fired in rapid succession until the trigger is released. Title II of the Federal firearms laws highly regulates fully automatic weapons. As an example, the M-16 military rifle has been produced with a fully automatic capability, although some versions have selective fire and can operate semi-automatically or in bursts. 
     Semi-automatic weapons with certain features mimicking the M-16 rifle or other military weapons are defined as “assault” weapons (e.g. the AR 15 rifle). 
     Weapons with some of those disfavored features have been banned in a number of states, and were temporarily banned on the Federal level. These disfavored features include high-capacity or detachable magazines, forward grips, barrel shrouds, bayonet lugs, threaded muzzles, and military-style pistol grips and butt stocks. 
     Some of these disfavored features may be considered reasonable for sporting and hunting purposes. In any event, the owners and prospective purchasers of such assault rifles (or handguns) are reasonably concerned that these weapons will be declared illegal or will become subject to intrusive regulations. 
     Accordingly, there is a need to adapt certain weapons to accommodate existing laws or foreseeable changes in the laws. 
     Referring to  FIG. 1 , a conventional semiautomatic weapon  14  is shown partially disassembled. Lower receiver  48  includes a trigger  48 A, grip  48 B, butt  48 D, and receptacle  48 E. Bolt  50  is placed in the forward end of bolt carrier  16 . Carrier  16  has on top and in front a conventional key  52 . Bolt carrier  16  is slid into the rear opening  42 A of upper receiver  42 . Gun barrel  20  is attached coaxially to the front of upper receiver  42 . Upper receiver  42  has a mounting collar  42 B, and barrel  20  has a mounting collar  54 . 
     Upper cowl  30  and lower cowl  31  connect together to form a conventional hand guard (together referred to as hand guard  33 ). Cowl  30  has on top a series of parallel projections  30 A forming a conventional Picatinny rail. Each of the projections  30 A has a short stub supporting a plate with tapered, wedge-shaped edges. Similar parallel projections  30 B on the right of cowl  30  also act as a Picatinny rail. Lower cowl  31  has on its underside a series of projections  31 A and on the left a series of projections  31 B, both sets of projections also acting as a Picatinny rail. Picatinny rails are well known for mounting accessories such as a rifle scope, handgrip, etc. In some cases a Picatinny rail may be formed from a rectangular plate having a face with rectangular parallel ridges running between right and left edges that are tapered and wedge-shaped. 
     Hand guard  33  mounts into collars  42 B and  54  to form a sleeve that encircles barrel  20  and gas tube  18 . The back end of gas tube  18  is shown slid into socket  52 A of key  52 . As shown in  FIG. 5A , the forward end of gas tube  18  is inserted into gas port  56 A of component  56  and held in place by pin  18 A. Port  56 A communicates through channel  56 B to vent  32  in barrel  20 . 
     When semiautomatic weapon  14  is assembled, the user may pull back a charging handle  57 , which retracts bolt carrier  16  and bolt  50  in well-known manner. A conventional mechanism in lower receiver  48  will then load a round of ammunition (not shown) into upper receiver  42  in front of bolt  50 . When this retraction reverses, bolt carrier  16  is driven forward by a spring (not shown) to thrust the ammunition into the breech of barrel  20 , which is then closed by bolt  50 . When trigger  48 A is pulled a hammer (not shown) in lower receiver  48  strikes a firing pin (not shown) in bolt  50  to fire the ammunition so that combustion gas drives a bullet (not shown) through barrel  20 . 
     When this bullet passes vent  32  the exhaust gas is fed through channels  56 B and  56 A into gas tube  18 . This very high pressure gas impinges against bore  52 A ( FIG. 5A ) in key  52 , driving bolt carrier  16  rearwardly. This rearward kinetic energy is used to strip the spent cartridge (not shown) and eject it out of receiver  42  before automatically loading a fresh cartridge in front of bolt  50 . Bolt carrier  16  is then returned by spring pressure to load the new round of ammunition in the breech of barrel  20  and close bolt  50  in the breech. 
     When trigger  48 A is next pulled exhaust pressure in tube  18  causes the foregoing cycle to repeat, with bolt carrier  16  and bolt  50  retracting, ejecting the spent cartridge, and returning to load a fresh round of ammunition into the breech of barrel  20 . This semi-automatic cycle occurred without the need to operate the charging handle  57 . Another cycle can be initiated by firing another round, once again sending combustion gas through tube  18  to retract bolt carrier  16 , strip the spent cartridge, before loading a new round, and driving bolt carrier  16  into a charged position ready for firing. 
     SUMMARY OF THE INVENTION 
     In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a method employing a carriage and pushing member for eliminating semi-automatic features from a weapon. The unmodified weapon has a bolt carrier that is reciprocated by a gas tube communicating with a barrel. The method includes the step of eliminating the gas tube. Another step is reciprocatably mounting the carriage at the barrel, forward of the bolt carrier with the pushing member connecting between the carriage and the bolt carrier. The method also includes the step of manually reciprocating the carriage to reciprocate the push member and the bolt carrier. 
     In accordance with another aspect of the invention, a kit is provided for eliminating semi-automatic features from a weapon. The unmodified weapon has a bolt carrier that is reciprocated by a gas tube communicating with a barrel. The kit includes a carriage adapted to be reciprocatably mounted around the barrel. The kit also has a pushing member that connects to the carriage and is adapted to be connected to the bolt carrier in order to reciprocate it by manually reciprocating the carriage. 
     By employing a kit and methods of the foregoing type, one is able to easily and efficiently modify a semiautomatic weapon into a manually cycled weapon. In a disclosed embodiment a semiautomatic weapon is partially disassembled to separate the hand guard, gas tube, upper and lower receiver, bolt carrier, and the key on the carrier. The gas tube, key, and hand guard are to be replaced. The exhaust port that previously held the forward end of the gas tube is then sealed with a plug that is held in place with the same pin that previously held the gas tube. 
     Before reassembling the weapon, the key on the bolt carrier will be replaced with a new key having a threaded bore. This threaded bore is adapted to receive the rear, threaded end of a pushrod instead of the gas tube. The forward end of this pushrod connects to a cylindrical carriage designed to encircle the weapon&#39;s barrel. Specifically, the carriage is formed of two semi-cylindrical shells that are hinged on the pushrod, which allows the carriage to open and close around the barrel. In other embodiments the carriage can be a simple tube that is installed by temporarily removing components on the front of the barrel. In any event, the first stage of assembly is completed with the bolt carrier reinstalled in the upper receiver and the pushrod connected between the carriage and the bolt carrier&#39;s key. 
     With the carriage closed around the weapon&#39;s barrel, a modified hand guard is installed around the barrel, carriage and pushrod. A spacer is inserted through a lower slot in the hand guard for attachment to the carriage. Screws are inserted through a Picatinny plate and the spacer before being screwed into the carriage to hold it closed and affixed to the spacer and plate. A hand grip can then be installed on the Picatinny plate. 
     The spacer has a latch mechanism that can hold the spacer and grip in the forward position. Some embodiments may use an alternate grip with a semi-cylindrical shape that allows the weapon to the operated in the style of a pump shotgun. 
     Initially, the modified weapon can be charged in the usual fashion with the pre-existing charging handle and then fired. Since the gas tube was removed, the weapon will not semiautomatically reload. Instead, the user will release the latch, pull back the grip, which retracts the carriage and bolt carrier in order to discharge the spent cartridge and reload a new round. When the grip is returned to the forward position, the new round is loaded into the breech before locking the bolt in place. The latch will then hold the handle in the forward position, and the weapon can now be properly fired. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above brief description as well as other objects, features and advantages of the present invention will be more fully appreciated by reference to the following detailed description of illustrative embodiments in accordance with the present invention when taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a prior art, semiautomatic weapon that has been partially disassembled; 
         FIG. 2  is a perspective view of the semiautomatic weapon of  FIG. 1  with modifications in accordance with principles of the present invention; 
         FIG. 3  is an elevational, fragmentary view of the weapon of  FIG. 2 , partly in section, and after assembly; 
         FIG. 4  is a perspective view of the carriage and pushrod of  FIG. 2  with the carriage open and the pushrod ready for insertion; 
         FIG. 5A  is an elevational, sectional view of portions of the prior art weapon of  FIG. 1  when assembled; 
         FIG. 5B  is an elevational, sectional view of portions of the weapon of  FIG. 5A  after being modified in the manner proposed in  FIG. 2 ; 
         FIG. 6A  is an elevational, cross-sectional, fragmentary view of a carriage and hand guard that is an alternate to that of  FIG. 2 ; 
         FIG. 6B  is an elevational, cross-sectional, fragmentary view of a carriage and hand guard that is an alternate to that of  FIG. 6A ; 
         FIG. 7A  is an elevational, fragmentary view of the pushrod of  FIG. 2 ; 
         FIG. 7B  is an elevational, fragmentary view of a pushrod that is an alternate to that of  FIG. 7A ; 
         FIG. 8  is a perspective, pre-assembled view of a hand guard and carriage that is an alternate to those previously illustrated; 
         FIG. 9  is an elevational view, partly in section, of the weapon of  FIG. 3 ; 
         FIG. 10  is a perspective, pre-assembled view of a hand guard, carriage, and grip that is an alternate to those previously illustrated; 
         FIG. 11  is a cross-sectional, assembled view of the apparatus of  FIG. 10 ; 
         FIG. 12  is a perspective, exploded view of a latch, plate, and spacer that is an alternate is that of  FIG. 2 ; and 
         FIG. 13  is an elevational, assembled view, partly in section, of the apparatus of  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 2 , lower receiver  48  and upper receiver  42  with its barrel  20  are the same as in  FIG. 1 . The bolt carrier  16  is the same as before except that key  52  of  FIG. 1  has been replaced with a modified key  152  as shown in  FIG. 5B . Specifically, key  152  has a bore  152 A with internal threads. 
     It will be appreciated that the foregoing elements (elements  16 ,  20 ,  42 , and  48 ) constitute almost all of the components of the weapon  14  illustrated in  FIG. 1 . As described further hereinafter, weapon  14  will be modified by removing and retiring the previously mentioned gas tube, key, and hand guard (gas tube  18 , key  52  and hand guard  30 / 31  of  FIG. 1 ). The replacement components and some additional new components are part of a kit used to eliminate the semiautomatic features of weapon  14 , and this modified weapon will now be referred to as manually cycled weapon  14 ′. It will be understood that the present disclosure contemplates modifying a variety of semiautomatic weapons, not just the one shown in  FIGS. 1 and 2 . 
     In  FIG. 5B , stopper  46  is a relatively short, solid rod that has been installed in previously mentioned gas port  56 A of component  56 , with its flat head covering port  56 A to provide additional sealing. Pin  18 A is inserted through a complementary hole of stopper  46  to hold it in place. Accordingly, combustion gases in barrel  20  will not escape through gas port  56 A. In  FIG. 5B , bore  152 A is threaded to accept the threaded end  12 A of pushrod  12  (also referred to as pushing member  12 ). 
     In  FIG. 4  the main section of pushrod  12  has an opposing pair of flats  12 D (one visible in the Figure) for receiving an open-end wrench. The forward end of pushrod  12  beyond shoulder  12 C is more slender and terminates in threads  12 B. Shoulder  12 C is shown in further detail in  FIG. 7A , but a modified pushrod  112  in  FIG. 7B  replaces the shoulder with flange  112 C. Flange  112 C has opposing flats  112 D (one visible here) that can be used by a wrench. 
     Referring to  FIGS. 2-4 and 9 , carriage  24  comprises a complementary pair of semi-cylindrical shells  24 A and  24 B. Shells  24 A and  24 B each have a pair of ventilation openings  36 A and  36 B, respectively. Shell  24 A has three knuckles  24 A- 1  interdigitating with the two knuckles  24 B- 1  of shell  24 B. The slender portion of pushrod  12  is inserted through the knuckles  24 A- 1  and  24 B- 1  up to the shoulder  12 C in order to act as a hinge pin. Pushrod  12  is held in place by threading nut  58  onto threads  12 B at the end of the pushrod. 
     The distal lip of shell  24 A is relieved on the inside to form blade  24 A- 2 . The distal lip of shell  24 B is relieved on the outside to form blade  24 B- 2 . Shells  24 A and  24 B are designed to swing together to encircle barrel  20 . Also, blades  24 A- 2  and  24 B- 2  are designed to swing together and overlap ( FIG. 9 ) with threaded screw holes  24 A- 3  and  24 B- 3  aligned. 
     Four rollers  62 A ( 62 B) are mounted along the centerline of shell  24 A ( 24 B) between the openings  36 A ( 36 B). The axis of rotation of rollers  62 A and  62 B are radially aligned with the cylindrical curvature of shells  24 A and  24 B, respectively. It will be appreciated that a different number of rollers can be used in other embodiments. 
     In  FIG. 2 , accessory plate  28  is arranged as a Picatinny rail with a number of parallel, rectangular ridges  28 A extending transversely between two opposite, wedge-shaped edges  28 B. Rail  28  has screw holes  28 C. Grip  26  may be mounted on rail  28 . 
     Spacer  42  is a rectangular block with screw holes  42 A. A pair of parallel, rectangular arms  42 B extending from the forward face of spacer  42  have aligned apertures for receiving pin  62 , which acts as a pivot for latch  38 . As shown in  FIGS. 2 and 4 , screws  60  are inserted through holes  28 C and  43 A in order to attach accessory rail  28  and spacer  42  to screw holes  24 A- 3  and  24 B- 3  of carriage  24 . 
     Latch  38  has an L-shaped plate formed of upright branch  38 A and transverse branch  38 B. Trigger  38 C extends downwardly from the back of branch  38 B and is widened for finger comfort. Pin hole  38 D at branch  38 B is designed to receive and pivot on pin  62 . Helical compression spring  64  mounts in a cavity (not shown) between arms  43 B of spacer  43  and is designed to bear against the lower inside corner of branch  38 B. 
     Referring to  FIGS. 2, 3 and 9 , upper cowl  130  and lower cowl  131  are part of a modification kit and connect together to form a hand guard (together referred to as hand guard  133 ). Hand guard  133  replaces previously mentioned hand guard  33  ( FIG. 1 ). Upper cowl  130  is similar to previously mentioned cowl  30  and has on top a series of parallel projections  130 A forming a conventional Picatinny rail. Each of the projections  130 A has a short stub supporting a plate with tapered, wedge-shaped edges. Similar parallel ridges  130 B on the right of cowl  130  and parallel ridges  131 B on the left of cowl  131  also act as Picatinny rails. 
     Rectangular groove  130 C underneath projections  130 A provides clearance for hinge knuckles  24 A- 1  and  24 B- 1  of carriage  24 . Rectangular notch  130 D ( 131 D) underlying projection  130 B ( 131 B) provide a track for roller  62 A ( 62 B). The tips of flange  130 E of upper cowl  131  and flange  131 E of lower cowl  131  fit into mating notches under projections  130 B and  131 B, respectively. 
     Previously mentioned spacer  43  is shown in  FIGS. 3 and 9  projecting through lower slot  40  in shell  131 . Slot  40  runs axially along most of the length of shell  131  without reaching either the forward or rear end of the shell. As shown in  FIG. 3  spacer  43  occupies the forward end of slot  40 . Forward of slot  40 , upright branch  38 A of latch  38  is shown lodged in rectangular hole  66  in cowl  131 , which hole is aligned with and spaced from slot  40 . 
     To facilitate an understanding of the principles associated with the foregoing apparatus, its operation will be briefly described. The owner of weapon  14  will obtain a kit including pushrod  12 , key  152 , stopper  46 , hand guard cowls  130  and  131 , carriage shells  24 A and  24 B, accessory rail  28 , and spacer  42 , (the spacer is preassembled with latch  38 ). Grip  26  can be optionally supplied with the kit, although this grip is conventional and can be acquired from traditional sources either before or after obtaining the kit. 
     Weapon  14  will be initially disassembled as shown in  FIG. 1 . Gas tube  18  is originally held in place by a pin (see pin  18 A of  FIG. 5A ) and can therefore be easily removed. Thereafter, stopper  46  is pinned in place using pin  18 A to seal bore  56 A. Also at this time, key  52  ( FIG. 1 ) can be removed and replaced with key  152  having the threaded bore  152 A shown in  FIG. 5B . Bolt carrier  16  can then be reinstalled in upper receiver  42 . 
     Next, the owner (or a technician hired by the owner) will interdigitate carriage knuckles  24 A- 1  and  24 B- 1  and insert through them the forward end of pushrod  12 . Carriage shells  24 A and  24 B are initially spread apart as shown in  FIG. 4  in order to place them around barrel  20 . The threaded rear end  12 A of pushrod  12  is then screwed into bore  52 A′ of key  52 ′ ( FIG. 5B ) and nut  58  is threaded on the forward end  12 B of the pushrod. A wrench can be placed on flats  12 D during this phase. Also bolt carrier  16  can be partially retracted for this assembly operation. One or more of the screws  60  may be temporarily threaded into holes  24 A- 3  and  24 B- 3  to hold the alignment of shells  24 A and  24 B. 
     Hand guard cowls  130  and  131  may then be installed in collars  42 B and  54  in the usual fashion, thereby encircling barrel  20  and carriage  24 . Cowls  130  and  131  will be held together by screws (not shown). Rollers  62 A ( 62 B) will fit in notch  130 D ( 131 D), and will be captured by flange  131 E ( 130 E). 
     Screws  60  will be removed from holes  24 A- 3  and  24 B- 3  and inserted up through holes  28 C of rail  28  and holes  43 A of spacer  43  before being screwed again into holes  24 A- 3  and  24 B- 3 . Grip  26  may be installed on accessory rail  28  in a conventional manner. 
     At this time, bolt carrier  16  can be pushed forward in upper receiver  42 . Upper receiver  42  will then be installed in receptacle  48 E of lower receiver  48 . An internal spring (not shown) in lower receiver  48  will keep bolt carrier  16  in its forward position, which will push rod  12  and carriage  24  to the forwardmost position as shown in  FIG. 3 . Consequently, upright branch  38 A of latch  38  will fall into hole  66  with the urging of spring  64  ( FIG. 2 ). 
     Weapon  14 ′ can be initially charged by depressing latch trigger  38 C to retract upright branch  38 A of latch  38  from hole  66 . The operator will now pull grip  26  back, causing carriage  24  to retract as its rollers  62 A and  62 B ride in notches  130 D and  131 D. Retraction of carriage  24  pushes rod  12  back against key  152 , causing bolt carrier  16  to retract as well. This retraction causes the usual operations, namely, ejection of any spent cartridge, and loading of a new round of ammunition. After completing full retraction, grip  26  can be moved forward to feed the new round of ammunition into the breech of barrel  20  before finally locking bolt  50  in the breech. 
     In the forward position, latch trigger  38 C can be released to allow upright branch  38 A to return into hole  66 . Even if latch trigger  38 C is released prematurely, the inclined leading edge of upright branch  38 A will be cammed downwardly when reaching the end of slot  40  and will eventually reach and snap into hole  66 , under the influence of spring  64 . The latching caused by latch  38  is designed to prevent inadvertent retraction of grip  26 , which could result in retraction of bolt carrier  16  and bolt  50 , resulting in weapon  14 ′ coming out of battery and disabling the weapon. 
     To fire weapon  14 ′, trigger  48 A is pulled to cause the hammer (not shown) in lower receiver  48  to strike the firing pin (not shown) in bolt  50  to discharge the ammunition in front of the bolt  50 . In this modified weapon  14 ′, stopper  46  prevents combustion gas from flowing through bore  56 A. Therefore, bolt carrier  16  remains in the forward position with bolt  50  in the breech of barrel  20 . 
     To load a new round of ammunition, the operator must first depress latch trigger  38 C before retracting grip  26  in order to cycle bolt carrier  16  and bolt  50  as before. The cycle is completed when bolt carrier  16 , bolt  50  and grip  26  are locked in the forward position with handle  26  latched in place by latch  38 . The weapon  14 ′ can be fired again followed by a repetition of the foregoing cycle. 
     Referring to the alternative embodiment of  FIG. 6A , shells  424 A and  424 B correspond to the previously mentioned shells  24 A and  24 B ( FIG. 9 ) but have different bearings for allowing sliding motion in upper hand guard cowl  430  (corresponding to hand guard cowl  130  of  FIG. 9 ). Accordingly, features of shells  424 A and  424 B corresponding to those of shells  24 A and  24 B bear the same reference numeral but increased by 400. Also, features of cowl  430  corresponding to those of cowl  130  bear the same reference numerals but increased by 300. 
     In particular, shells  424 A and  424 B have open cylindrical clips  462 A and  462 B, respectively. The inside of cowl  430  has a ridge  430 F with a cylindrical rail sized to snap into clip  462 B. It will be appreciated that clip  462 A can snap over a corresponding ridge (not shown). Accordingly, shells  424 A and  424 B can slide longitudinally on their clips  462 A and  462 B. 
     Referring to the alternative embodiment of  FIG. 6B , shell  524 A correspond to the previously mentioned shell  24 A ( FIG. 9 ) but has different bearings for allowing sliding motion in hand guard  530 / 531  (corresponding to hand guard  130 / 131  of  FIG. 9 ). Accordingly, features of shell  524 A corresponding to those of shell  24 A bear the same reference numeral but increased by 500. Also, features of hand guard  530 / 531  corresponding to those of hand guard  130 / 131  bear the same reference numerals but increased by 400. 
     In particular, shell  524 A has a longitudinal, rectangular ridge  562 A size to fit in the notch  530 D formed in cowl  530 . It will be appreciated that a similar rectangular ridge and notch exists on the opposite side. Accordingly, shell  524 A can slide longitudinally in notch  530 D by means of ridge  562 A. 
     Referring to the alternative embodiment of  FIG. 12 , accessory rail  128  is similar to previously mentioned accessory rail  28  ( FIG. 2 ) but has an extended forward end with a longitudinal slot  128 D designed to receive latch  138 . Latch  138  is similar to previously illustrated latch  38  but has spring slot  138 E. Latch  138  is pivotally mounted in slot  128 D on pin  162 . Features of latch  138  and accessory rail  128  corresponding to the previously described latch  38  and rail  28  have the same reference numerals but increased by 100. 
     In this embodiment the previously described helical compression spring  64  has been replaced with leaf spring  164 , which has an upwardly curled forward end designed to fit into slot  138 E. Spacer  143  is a simple rectangular block with screw holes  143 A. As before, screws inserted through holes  128 C,  164 A, and  143 A will attach the assembly to the previously mentioned carriage (carriage  24  of  FIGS. 2, 3 and 9 ). 
     As shown in  FIG. 13 , latch  138  is not directly mounted on spacer  143 . Instead, latch  138  is mounted in slot  128 D of Picatinny rail  128 , which is shown again attached to previously mentioned grip  26 . Upright branch  138 A is shown inserted into hole  66 ′ of lower hand guard cowl  131 ′. Elements  66 ′ and  131 ′ have been marked with primes (′) to account for any required repositioning of hole  66 ′, otherwise lower hand guard cowl  131 ′ is the same as previously described. 
     With latch  138  installed as shown, the modified weapon will operate as previously described. In particular, latch trigger  138 C can be depressed to rotate latch  138  to pull upright branch  138 A out of hole  66 ′, which depresses the distal end of leaf spring  164 . Grip  26  and carriage  24  can be reciprocated as before to charge the weapon, which will be ready for firing when upright branch  138 A returns into hole  66 ′. 
     Referring to the alternative embodiment of  FIG. 8 , modified carriage  224  is shown arranged to slidably mount inside a hand guard composed of upper cowl  230  and lower cowl  231 . Carriage  224  and cowls  230  and  231  are like previously mentioned carriage  24  and cowls  130  and  131 , except that mounting knuckles  262 A- 1 ,  262 A- 2 , and  231 E replace rollers  62 A and  62 B and grooves  130 D and  131 D. Accordingly, features of carriage  224  corresponding to those of carriage  24  bear the same reference numeral but increased by 200. Also, features of cowls  230  and  231  corresponding to those of cowls  130  and  131  bear the same reference numerals but increased by 100. 
     Carriage  224  will be installed around the gun barrel as described before, with the backend of pushrod  12  attached to key  52 ′ as previously described. The forward end of previously mentioned pushrod  12  is inserted through knuckles  224 A- 1  and  224 B- 1 . 
     Shell  224 A is shown having an aligned pair of knuckles  262 A- 1  and  262 A- 2 . Knuckle  262 A- 1  is near the rear edge of shell  224 A, while knuckle  262 A- 2  is set back from the front edge of shell  224 A. Although not visible in this view, shell  224 B has a complementary pair of knuckles at the same elevation and longitudinal positions. 
     Knuckles  262 A- 1  and  262 A- 2  will be aligned with one of the pair of knuckles  231 E at the front edge of cowl  231 . It will be understood that a pair of knuckles at the rear edge of cowl  231  (not shown) are positioned in alignment with knuckles  231 E. 
     Carriage  224  can be placed around the weapon&#39;s barrel (barrel  20 ) with threaded spindles  268  in the knuckles  262 A- 1  and  262 A- 2  on shell  224 A and the unillustrated knuckles on shell  224 B. Cowl  231  is then placed under carriage  224  and threaded spindles  268  are passed through both knuckles  231 E in the front and the unillustrated knuckles in the back of cowl  131 . Thereafter nuts (not shown) are threaded on the opposite ends of spindles  268  to secure them in place, before securing cowl  230  in place. Accordingly, carriage  224  can slide back and forth on the shanks of spindles  268 . 
     As before, lower cowl  231  has a slot for receiving previously mentioned spacer  43 , which is attached, together with previously mentioned rail  28 , to the blades  224 A- 2  and  224 B- 2  of carriage  224 . Once the assembly is completed, the weapon can be used the same manner as previously described, except that now carriage  224  rides on the shanks of spindles  268 . 
     Referring to  FIG. 10 , a hand guard is formed of upper cowl  330  and lower cowl  331 , together referred to as handguard  333 . Handguard  333  is similar to previously mentioned handguard  133 , but projections  130 B and  131 B, and grooves  130 D and  131 D were eliminated. Each of the lower edges of cowl  330  has an elongate recess  340 . Cowl  330  has in the rear an opposing pair of lower lugs  330 F designed to attach to the two ends of the semicircular flange  331 F of lower cowl  331  by means of screws (e.g. screw S 1 ). Cowl  330  has in front an opposing pair of lower lugs  330 E designed to attach in a similar fashion to the two ends of the semicircular flange  331 E of lower cowl  331 . 
     Lower cowl  331  has along one of its upper edges a rectangular notch  366 , positioned just forward of recess  340  of upper cowl  330 . 
     The upper edges of quarter-cylindrical shells  368  and  370  are welded to cylindrical tube  369  to form a carriage. Pushrod  312  is substantially the same as the previously mentioned pushrod (pushrod  12  of  FIG. 4 ) and is installed in the key  52 ′ as before. The forward end of pushrod  312  is installed in tube  369  and held in place with a nut (not shown). 
     Quarter shells  368  and  370  have flanges  368 A and  370 A, respectively, that fit in recess  340  between cowls  330  and  331  when they are assembled around the previously mentioned gun barrel. 
     Shotgun-style handgrip  326  has a semi-cylindrical shape designed to embrace the semicylindrical outside surface of cowl  331  between flanges  331 E and  331 F. The upper edge of grip  326  is attached to flanges  368 A and  368 B by screws (e.g. screw S 2 ). Accordingly, carriage  368 / 370  can be longitudinally reciprocated by manually reciprocating grip  326 . 
     One front corner of grip  326  has a longitudinal slot  326 A near the top of the grip. Latch  338  is rotatably mounted in slot  326 A by pin  362  which passes through bore  326 C into the latch&#39;s pivot hole  338 D. Latch  338  has a latching branch  338 A that connects through crossmember  338 B to finger pad  338 C. One end of compression spring  364  is mounted in blind hole  326 B, while its other and fits into a blind hole (not shown) on the back of finger pad  338 C. Accordingly, when grip  326  is slid forward, latching branch  338 A will be driven into notch  366  by spring  364 . Latch  338  can be released by pressing finger pad  338 C to rotate the latch and withdraw latching branch  338 A from notch  366 . 
     Therefore, grip  326  can be used to cycle the weapon as described before. In particular, an operator will depress finger pad  338 C before pulling grip  326  back in order to eject a spent cartridge shell. Thereafter grip  326  is slid forward to load a new round of ammunition. Eventually, latching branch  338 A swings into notch  366  under the urging of spring  364 . At this time the gun bolt is locked in the breech and can be fired. 
     It is appreciated that various modifications may be implemented with respect to the above described embodiments. For example, carriage  24  need not necessarily be formed from two hinged semicylindrical shells. Instead the carriage may be a simple tube that will be installed by temporarily removing cap  54 , component  56  and any other components on the front of the barrel. Once this carriage is in place, the temporarily removed barrel components can be reinstalled. 
     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.