Convertible, belt/clip-fed automatic gun with positive shell casing ejection

An automatic gun comprises a barrel, a receiver connected to the barrel and a bolt and bolt carrier mounted in the receiver for recoil and counterrecoil movement between the barrel breech and a recoil position rearwardly of a shell pick up position and a casing ejection port. The bolt carrier has a cam track formed along it and the bolt has a pivotally mounted casing extractor and an ejection recess in an opposite region. The forward end of a cam follower is pivotally mounted to the receiver forwardly of the pick up position. The follower has a pair of belt feeding pawls mounted centrally, an inwardly-directed ejection tip at the rearward end and a cam track follower in engagement with the bolt carrier cam track. A belt feeding adaptor is detachably connected to the receiver above the cam follower for receiving an ammunition belt. In response to forward bolt carrier movement, the cam follower is pivoted outwardly, moving the feed pawls into engagement with a belted shell outboard of the pick up position. Corresponding forward bolt movement strips a shell from the pick up position and loads it into the breech. When the bolt carrier recoils after firing, the cam follower pivots inwardly and the feed pawls advance the belt one shell position. As the cam follower pivots inwardly, its ejection tip moves into the ejection recess in the bolt and causes ejection of a shell casing held to the bolt face by the extractor. An ammunition clip adapator is interchageable with the belt feeding adapter.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to the field of automatic guns and 
more particularly to light machine guns having the capability for 
alternatively firing belted and clip-fed ammunition. 
2. Background Discussion 
In spite of the development of such sophisticated and powerful weapons as 
nuclear bombs, ballistic and guided missles, supersonic fighters and 
bombers, super aircraft carriers and nuclear-powered submarines, modern 
military conflicts still ultimately rely upon foot troops whose combat 
role is, as it has always been, to take and hold ground. This apparent 
anomoly has been demonstrated time and time again in post-World War II 
conflicts, including the Korean war, Viet Nam, Granada and the current 
Iraq-Iran conflict in the Mid-East. 
For several hundred years, the primary weapon of ground troops has been the 
rifle. Starting with crude, single shot, match-lock muzzle loaders, the 
rifle has evolved through breech-loaders and semi-automatic rifles, into 
the present day, relatively small calibre, clip-fed. automatic rifles, 
exemplified in the United States and many other free countries of the 
world by the M-16 and in Soviet-block countries by the AK-47. 
In most military organizations, rifles have typically been supplemented, on 
a company, platoon or squad level, by submachine guns (which fire pistol 
ammunition) and light machine guns (which fire rifle ammunition). By way 
of example, in both World War II and Korea, the semi-automatic M1 rifle 
used by U.S. troops was augmented by such automatic weapons as the 
Thompson submachine gun, the "grease" gun, the Browning automatic rifle 
(BAR) and 30 and 50 calibre machine guns, and in Viet Nam the M-16 was, 
for example, augmented by the larger, NATO calibre M-60 machine gun. 
Many modern automatic rifles, such as the M-16 and the AK-47, as well as 
various other similar rifles in service throughout the world, combine 
features which were once separately found in rifles, submachine guns and 
light machine guns. The resulting modern rifles, which are usually 
selectable between semi-automatic and fully automatic firing, are 
sometimes referred to generically as "assault rifles." 
Although modern automatic rifles usually have many advantages over those 
used in World War II and Korea, being generally lighter in weight and 
having greatly increased fire power, improvements are still continually 
sought by the military services not only in automatic rifles but also in 
ligth machine guns (LMG) which are easily carried by troops and which 
increase the firepower and effectiveness of the troops in both offensive 
and defensive situations. 
One relatively recent requirement, at least by the military in this 
country, for new generation LMG's is that such weapons have the dual 
capability for firing both belted ammunition and ammunition held in 
conventional, rifle clips. The use of belted ammunition, which is, in one 
configuration, held in boxes which attach to the gun, enables sustained 
firing without reloading the gun. On the other hand, the ability to use 
standard rifle clips which hold the same calibre ammunition and which are 
commonly available in rifle companies using the LMG's, enables continued 
operation of the LMG if the supply of belted ammunition is exhausted. 
Although some types of belt and clip-fed, "convertible" LMG's have been put 
into limited service, that does not necessarily mean that such guns are 
entirely satisfactory for combat use or that they cannot or should not be 
improved upon. Extensive, individualized "gunsmithing" is, for example, 
reportedly required on some types of convetable LMG's before they are 
capable of satisfactory operation even in benign environments. This raises 
questions as to the reliability of such guns in service and especially 
under combat conditions, and improvements to overcome this apparent 
manufacturability problem are expected to be needed. 
It is desirable in such convertible guns to reduce the number of small 
and/or complicated parts. Complicated parts are not only costly to 
manufacture but often make the interchageability of parts difficult. 
Among other requirements, LMG's should: (i) be rugged and operate reliably 
and accurately, in a wide range of hostile environments, including arid 
and sandy deserts, humid jungles and icy polar regions, (ii) be capable of 
taking all manner of abuse and still operate satisfactorily; (iii) not 
require excessive maintanance and whatever maintenance is required should 
be quick and simple to perform both under adverse field conditions and by 
relatively untrained troops, (iv) not have an excessive number of 
complicated parts which can be easily damaged or which cannot be 
interchanged among weapons of the same type, (v) be easy to operate 
accurately by relatively green troops, and (vi) be relatively simple and 
economical to manufacture. 
The importance of this country's having the best possible weapons, 
including LMG's, for its troops is made evident by the fact that in any 
armed conflict, United States troops can be expected to be out numbered by 
enemy troops, often by a large margin. It is, therefore, a principle 
objective of the present invention to provide an improved, convertible 
belt/clip-fed automatic gun or LMG which will overcome the deficiencies of 
known guns of such type. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a convertible, belt/clip-fed 
automatic gun, such as a light machine gun, comprises a barrel having a 
breech and a receiver connected to the barrel and having a battery 
position disposed adjacent the barrel breech, a shell pick up position and 
a shell casing ejection port. A bolt assembly, comprising a bolt and a 
bolt carrier, is slidably mounted in the receiver for reciprocating 
movement, in response to firing of the gun, between the battery position 
and a recoil position rearwardly of the shell pick up position and the 
shell casing ejection port. The bolt assembly includes means for picking 
up a shell from the pick up position upon forward bolt assembly movement, 
for loading the picked up shell into the breach and, after firing, for 
extracting the fired shell casing and ejecting it outwardly through the 
ejection port upon rearward recoil movement from the breech towards the 
recoil position. 
Further comprising the gun are ammunition belt receiving and advancing or 
feeding means which include a cam follower pivotally mounted to the 
receiver, at least one belt advancing pawl mounted to the cam follower, a 
belt feeding adapter for receiving an ammunition belt and means for 
releasably attaching the belt feeding adapter to the receiver adjacent to 
the shell pick up position and in an operative relationship with the cam 
follower. The cam follower has a portion thereof in movable engagement 
with a cam track formed on the bolt assembly, preferably on the bolt 
carrier, the cam follower being shaped so that upon rearward movement of 
the bolt assembly (and thus, the cam track) from the breech to the recoil 
position, for example, by a firing of the gun, the belt advancing pawl is 
moved inwardly towards the bore axis to inwardly advance, by one shell 
position, an ammunition belt held by the belt feeding adapter in a manner 
moving a shell held in the belt into the shell pick up position. The cam 
follower is also responsive to forward movement of the bolt assembly from 
the recoil position to the breech for moving the belt advancing pawl a 
shell distance outwardly in readiness for advancing the belt the next time 
the bolt assembly is moved rearwardly to the recoil position. 
The bolt assembly includes a shell extractor and an ejector recess in a 
region opposite the extractor. The cam follower includes a shell ejector 
portion which is caused by the bolt carrier cam, responsive to the bolt 
assembly moving rearwardly from the the breech to the recoil position and 
pivoting of the cam follower, to move into the ejector recess and cause 
ejection of a shell casing held by the shell extractor as the bolt 
assembly continues to recoil rearwardly to a preestablished position 
relative to the shell ejection port. 
There is also included as part of the gun an ammunition clip holder and 
means for releasably attaching the clip holder to the receiver in place of 
the belt feeding adapter and out of engagement with the belt advancing 
pawl. The clip holder is preferably constructed to receive and feed shells 
from a conventional rifle clip and for holding the clip directed upwardly 
and at an angle relative to a vertical plane through the bore axis which 
does not interfere with use of the gun sights. 
According to a preferred embodiment of the invention, the belt feeding 
adapter includes at least one shell anti-back up pawl for preventing a 
shell in the pick up position from being moved outwardly away from said 
position when the belt advancing pawl is moved outwardly in response to 
forward movement of the bolt assembly. 
It is preferred that the cam follower be pivotally mounted at a forward 
region to the receiver and that the cam track engaging portion be rearward 
of the pivotal mounting region. Also, it is preferred that the belt 
advancing pawl is pivotally mounted to the cam follower and is 
spring-loaded so that when the cam follower is pivoted outwardly, in 
response to forward movement of the bolt assembly, the pawl pivots to a 
retracted position as the pawl is pushed outwardly under a shell in the 
belt to a position which enables the pawl to advnce the belt one shell 
position when the cam follower is next pivoted inwardly in response to the 
bolt assembly moving back rearwardly from the breech. 
In the preferred embodiment, the belt feeding adapter comprises a lower, 
body portion and an upper, cover portion, the body and cover portions 
being hinged together so that the cover porton can be opened relative to 
the body portion without detaching the adapter from the receiver, an 
ammunition belt being insertable in the adapter when the coverportion is 
open and being retained in the adapter when the cover portion is then 
closed.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Illustrated in FIG. 1a is an examplary light machine gun (LMG) 10 in which 
the present invention may be used to advantage. Shown comprising gun 10 is 
a receiver 12 to which a barrrel 14 is connected. A collapsible shoulder 
member or stock 16 projects rearwardly from receiver 12 and a conventional 
pistol grip-type handle and trigger group 18 are connected to lower, rear 
regions of the receiver. A bipod assembly 20, for example, of the type 
used on an M-60 machine gun, is connected to rearward regions of barrel 
14. Just rearwardly of bipod assembly 20 is a hand guard-grip assembly 22 
which encloses rearward regions of barrel 14 and/or forward regions of 
receiver 12. 
Detachable connected to the bottom of receiver 12, forwardly of handle and 
trigger group 17, is a box magazine 30 which holds a flexible belt 32 of 
ammunition (i.e., shells) 34 for gun 10. Ammunition belt 32 is of the 
disintegrating link type in which adjacent links 36 are interlocked by 
shells 34, the stripping of shells causing the links to separate so they 
can be separately discharged from gun 10, as described below. 
In accordance with the present invention, and as described below, an 
ammunition belt adapter assembly 40 is detachably connected to the 
lefthand side (as shown in FIG. 1) of receiver 12 for enabling the firing 
by gun 10 of shells 34 from belt 32. Shown in operative relationship with 
belt adapter assembly 40 is a cam follower assembly 46 which provides not 
only for the advancing of ammunition belt 32 into gun 10, so that shells 
34 held by the belt can be fired, but also for the ejection of fired shell 
casings through the other side of receiver 12, as described below. 
Although gun 10 is, as a light machine gun, primarily intented for firing 
belted ammunition, as is enabled by belt adapter assembly 40 and cam 
follower assembly 46, emergency situations may arise during combat in 
which supplies of belted ammunition for the gun may run out. In order to 
enable continued operation of gun 10 in such situations, albeit with 
reduced fire power, there is included the provision for alternatively 
using standard rifle ammunition clips which may, in some situations, be 
more plentiful than belted ammunition. Accordingly, as depicted in FIG. 
1b, which shows only shell feeding regions of gun 10, ammunition belt 
adapter 40 may be substituted, also as more particularly described below, 
by a clip feeding adapter assembly 48 which then permits the firing by the 
gun of shells held in a conventional rifle clip or magazine 50. By way of 
example, assuming that gun 10 is configured for firing standard 5.56 mm 
(i.e., 223 calibre) ammunition which is used in the M-16 rifle, clip 
adapter assembly 48 is preferably configured for receiving a standard M-16 
clip 50. As can be seen from FIG. 1b, when belt adapter 40 is replaced by 
clip adapter 48, box magazine 30 is removed from a dovetail slot 52 in 
receiver 12. Also, parts of cam follower assembly 46 are, as described 
below, removed to accomodate clip feeding adapter assembly 50. 
FIG. 2 shows, in exploded perspective, relevant shell feeding and ejecting 
regions of gun 10 to which belt and clip adapter assemblies 40 and 48, 
respectively, are detachably connected. Shown in FIG. 2, in addition to 
forward regions of receiver 12 and rearward regions of barrel 14, are belt 
adapter assembly 40, clip adapter assembly 48, cam follower assembly 46 
and a bolt group 54. 
It is to be noted that in FIG. 2 and subsequent FIGS. gun 10 is pointing to 
the right; whereas, in order to show features not otherwise clearly 
visible, FIGS. 1a and 1b depict the gun pointing to the left. 
Principally comprising ammunition belt adaptor assembly 40, as shown in 
FIG. 2, are an adaptor base 56 and a cover assembly 58. In turn comprising 
cover assembly 58 are a upwardly recessed cover plate 60, a shell stripper 
62, a shell pusher 64 and a shell holding or anti-back up pawl 66. Shell 
pusher 64 is formed having a pair of similar, longitudinally spaced apart, 
outwardly directed ears 72 through which are formed a pair of 
longitudinally aligned mounting apertures 74. Formed along the rearward 
edge of shell pusher 64 is a downwardly projecting, wedge-shaped shell 
pushing portion 76. Shell stripper 62 is generally square in plan view and 
has a mounting aperture 78 formed longitudinally through an outer end 
region thereof. Formed upwardly into shell stripper 62, at a inner, 
rearwardly corner of the stripper is a recess 80 which receives forward 
regions of belt links 36 when a shell 34 is being stripped out of 
ammunition belt 32 during firing of gun 10 and holds the link in place 
(i.e., prevents forward movement of the link as the shell is pushed 
forwardly during the stripping operation). Anti-back up pawl 66 is formed 
having a pair of outwardly projecting, longitudinally spaced apart, 
parallel ears 82 interconnected at inner end by a pawl portion 84. A pair 
of longitudinally aligned mounting apertures 86 are formed through outer 
end regions of ears 82. Upon assembly, anti-back up pawl 66 is positioned 
between shell pusher ears 72 with mounting apertures 86 and 74 aligned, 
and with a coil-type torsion spring between pawl ears 82. 
An elongate pin 96, extends longitudinally through apertures (not shown) in 
cover plate 60 and through shell pusher apertures 74, pawl apertures 86, 
spring 94 and stripper apertures 78. Pin 96 pivotly mounts shell pusher 64 
and stripper 62 in a side-by-side relationship, with the stripper 
forwardly of the pusher and with anti-back up pawl 66 between pusher ears 
72, within a rectangular recess formed upwardly into cover plate 60 and 
defined by an under surface 98 (FIGS. 3 and 5). Compression springs 100 
and 102, installed between inner end regions of shell pusher 64 and shell 
stripper 62, respectively, and cover plate under surface 98, when the 
shell holder and stipper are installed on pin 96, urge inner end regions 
of the pusher and stripper downwardly. Such downward pivoting is limited 
by the upper surfaces of outer ends of shell pusher 64 and stripper 62 
bearing against cover under surface 98. 
Further comprising cover assembly 58 (still referring to FIG. 2) are two 
opposing, spring loaded cover latches 104 which project sidewardly in 
opposite directions from a rearward end region 106 of cover 60. Latches 
104 are retained in end region 106 by a pair of vertical pins 107. 
Projecting forwardly from cover 60, and forming part thereof, are a two 
similar, laterally spaced apart arms 108, by means of which the cover 
assembly is attached to receiver 12. A pair of laterally aligned attaching 
apertures 110 are formed through forward end regions of arms 108 for 
receiving a removable mounting pin 112, as described below. 
Ammunition belt adapter base 56 is configured to mate with cover assembly 
58, described above, so that ammunition belt 32 (FIG. 1a) cam be fed 
therebetween from magazine 30 into gun 10. A recessed bottom region of 
base 56 is formed having a longitudinal shell feeding slot 114 which is 
narrower in rearward regions than in forward regions, the forward regions 
being sufficiently wide to permit a shell 34 being stripped forwardly from 
ammunition belt 32 to move downwardly through the slot and into a shell 
chamber 116 (FIG. 3) formed in the barrel 14 at the breech. Rearward 
regions of feeding slot 114 are narrower than a shell width so that shells 
34 moved into a shell pick up position 118 (FIG. 6, 8) at the slot are 
supported by adapter base regions on both sides of the slot. Two 
longitudinally spaced apart, lateral slots 120 (only a forward one of 
which is shown in FIG. 2) are formed in the botton of base 56, from shell 
feed slot 114 outwardly, to provide cleareance for a pair of belt 
advancing pawls 122, which, as described below, comprise part of cam 
follower assembly 36. 
A rectangular, belt link ejection port 124 is defined in an inboard side 
edge 126 of base 56 to enable the discharge of belt links 36 after a shell 
34 has been stripped from the link which is at feed slot 114. Projecting 
forwardly from adapter base 56 and forming a part thereof are two 
laterally spaced apart mounting arms 126 having mounting apertures 128 
formed therein for receiving mounting pin 112. Upon attachment of belt 
feeding adapter 40 to receiver 12, arms 108 of cover 60 fit inside of arms 
126 of base 56 and such arms slide downwadly into slots 136 in upper 
forward regions of the receiver until the apertures 110 and 128 in 
respective arms 108 and 126 are aligned with a mating transverse aperture 
138 formed through a receiver boss 140 and side ears 142 defined by slots 
136. Pin 112 is then inserted laterally through apertures 130, 128 and 
110, the pin being thereafter locked in place, as by the use of a detent 
pin 144 having a spring 146. When pin 112 is removed cover assembly 58 and 
base 56 can be removed as two pieces. When adapter base 56 and cover 
assembly 58 are pivoted closed on pin 112, latches 104 on cover 60 snap 
into a latching member 147 mounted on receiver 12 (FIG. 2). 
As shown in FIGS. 2 and 3, a barrel lock assembly 148 may advantageously 
also be installed on pin 112. Comprising barrel lock assembly are an 
operating lever 150, a barrel locking pin 152 a tubular bushing 154 and 
concentric compression springs 156 and 158. Lever 150 is formed having 
two, laterally spaced apart, depending legs 160, each of which has a 
mounting aperture 162 formed therethrough. When lock assembly 148 is 
attached to receiver 12, legs 160 straddle boss 140 and extend downwardly 
into slots 136 on either side of the boss. Bushing 154 is inserted, 
through an outer aperture 138 in righthand side ear 142, into the 
corresponding aperture in boss 140 and through lever leg apertures 162. 
In the above-described manner, lever 150 is locked to boss 140 and can 
pivot on bushing 154 which has clearance relative to the boss aperture. 
Upper ends of compression springs 156 and 158 are received into a shallow 
pocket 164 (FIG. 3) formed on the under side of lever 150 forwardly of 
mounting pin 112. Lower ends of springs 156 and 158 are received in a 
shallow recess 166 formed into a forward end region 168 of receiver 12. 
Barrel locking pin 152 is installed in a vertical aperture 170 formed 
downwarly through boss 140. Locking pin is fixed to lever legs 160 by a 
transverse pin 172 which extends through apertures 174 in legs 160 
rearwardly of apertures 162, through a vertically elongated slot 176, 
which extends transversely through boss 140 in the region of aperture 170, 
and through a transverse aperture 178 through locking pin 152. When so 
installed, springs 156 and 158 urge the lower end of locking pin 152 into 
an aperture 186 (FIG. 3) in a tubular bolt locking ring 188 threaded onto 
the reaward end of barrel 14, assuming, of course, that the barrel and 
locking ring are porperly oriented relative to the locking pin. 
When barrel locking assembly 148 is installed in the above described 
manner, a bushing 190 (FIG. 2) is installed in the side ear aperture 138 
through which bushing 154 is installed so that pin 112 fits properly. 
Cam follower assembly 46 (FIG. 2) principally comprises a cam follower 
member 200 and a belt (shell) advancing pawl assembly 202. Cam follower 
member 200 is formed having upper and lower mounting ears 204 and 206, 
respectively, at the forward end. Mounting apertures 208 and 210 are 
formed, in vertical alignment, through respective mounting ears 204 and 
206 for receiving a mounting pivot pin 212. A pair of mating mounting lugs 
214 project outwardly from the lefthand side of receiver 12 rearwardly 
adjacent to receiver side ears 142 (FIGS. 4 and 5) between which upper and 
lower ears 204 and 206, respectively, of cam follower member 200 fit and 
through which adapter mounting pin 112 is also installed to thereby 
pivotally attach cam follower assembly 46 to receiver 12. A coil torsion 
spring 216 installed on pin 112 between cam follower member ears 204 and 
206 urges the member to pivot about the pin in an inward direction (in the 
direction of arrow "A", FIG. 4). 
Projecting inwardly from a reawardly end region of cam follower member 200 
is a cam follower arm 220 (FIGS. 2, 4 and 5). Pivotally mounted to the 
inboard, distal end of cam follower arm 220 is a depending cam follower 
element 222. A reaward end of cam follower member is curverd inwardly to 
form a shell casing ejector 224 having a flat, forwardly directed, casing 
ejector face 226 (FIG. 4). 
Comprising belt advancing pawl assembly 202 (FIGS. 2, 4 and 5) is a 
T-shaped member 238 comprising a depending pivot pin 240 and an elongate 
arm 242 fixed to the top thereof. Two pairs of pawl mounting ears 244 
project upwardly from the top of arm 242, one pair of ears being at each 
end of the arm in a longitudinally spaced apart relationship. Pawl 
mounting apertures 246 are formed in ears 244 and correspondig apertures 
248 are formed through the outboard end of each pawl 122. With both pawls 
122 pointing inardly (FIG. 5) and one pawl inserted between each pair of 
ears 244, the pawls are pivotally mounted to member 238 by a mounting pin 
252 which extends rearwardly through all of apertures 246 and 248 and is 
retained in place by a detent (not shown). Torsion coil springs mounted on 
pin 252, between pawls 122, urge inboard ends of the pawls upwardly (FIG. 
5). Lower surface regions of pawls 122 beneath mounting pin 252 bear 
against an upper surface of arm 242 and limit pivotal movement of the 
pawls. 
Pivot pin 240 connects pawl assembly 202 to cam follower member 200, the 
pin being downwardly received through an aperture 256 formed vertically 
through the member about 2/3 of the distance rearwardly from member 
mounting pin 212 toward the ejector tip 224. A conventional C-ring 258 
(FIG. 2) may be used to retain pivot pin 240 in cam follower member 200. 
When pawls 122 are installed in the above described manner, they curve 
upwardly and inwardly (FIG. 5) so as to bear against a shell 34 in 
ammunition belt 32. 
Bolt group 54 (FIG. 2) comprises generally a bolt assembly 266 and a bolt 
carrier assembly 268. Bolt assembly 266 is mounted to bolt carrier 
assembly 268 in a generally conventional manner so that limited axial 
movement between them is permitted. In turn comprising bolt assembly is a 
bolt 270 having a forward face 272 (FIGS. 2 and 3) and a spring-loaded, 
shell casing extractor 274 mounted by a semi-cylindrical pivot ridge 276 
engaging a mating semi-cylindrical groove within recess 275 adjacent such 
forward face (FIGS. 7 and 9). An ejection recess 275 is cut into bolt 270 
opposite to casing extractor 274. 
Bolt carrier assembly 268 comprises a generally L-shaped carrier 278 having 
an elongate lower portion 280 and a shorter upper portion 282. Connected 
to a forward end region of carrier lower portion 280 is a forwardly 
directed, gas operated push rod. A rearwardly directed, elongate recoil 
rod 292 extends through a longitudinal aperture 294 in carrier lower 
portion 280 in axial alignment with push rod 290. Mounted around recoil 
rod 290, rearwardly of carrier 268, is a long recoil spring 293. 
Longitudinally mounted in an aperture 295 formed axially through carrier 
upper portion 282 along a barrel bore axis 296 (FIGS. 2 and 3) is an 
elongate firing pin 298 which is held in aperture 295 by an I-shaped 
locking element 300 which is installed downwardly into a circular aperture 
302 in carrier upper portion 282 on top of a compression spring 304. When 
locking element 300 is pushed downwardly against spring 304, firing pin 
296 is inserted through an aligned aperture 306 in the element. Then, when 
element 300 is released, spring 304 pushes the element upwardly so that 
portions of the element adjacent aperture 306 engage a groove 308 around 
rearward regions of the firing pin, thereby locking the firing pin in 
carrier upper portion 282. Although locking element 300 is thereby held in 
aperture 302 by firing pin 296, if the firing pin has to be repolaced, the 
element will be loose unless otherwise retained. For such retaining 
purpose, a slender, transverse pin 310 is installed in a transverse 
aperture 312 formed through carrier upper portion 282 in the region of 
locking pin aperture 306. When inserted in aperture 312, pin 310 is 
received in a recess 314 in a forward side of locking element 300. As a 
result, firing pin 296 can be removed without removing locking pin 312. 
Forward regions of firing pin 296 are received into a bore axis aperture 
formed through bolt 270 when bolt assembly 266 and carrier assembly 268 
are assembled together. 
Bolt assembly 266 is connected to carrier assembly 268 by a transverse 
camming pin 324 which is received in a recess 326 in bolt 270 and which 
extends into a flat L-shaped camming aperture formed through the inboard 
side of carrier upper portion 282. Camming pin 324 and camming aperture 
328 permit limited axial movement of bolt assembly 266 relative to carrier 
assembly 268 and permit the bolt assembly to rotate a partial turn so that 
the bolt assembly can be locked to a breech locking ring 188 (FIG. 2) when 
the bolt and carrier assemblies are driven forwardly, by recoil spring 
293, into their forwardmost, battery position. 
Importantly, as shown in FIGS. 2, 4, 5, 7 and 8, a substantially linear cam 
track 334 is formed downwardly into carrier lower portion 280 from an 
upper surface 336 thereof. Cam track 334 is angled outwardly and 
rearwardly at an angle, .alpha., with respect to barrel bore axis 296 
(FIG. 4). Preferably angle, .alpha., is between about 5.degree. and about 
10.degree., and is more preferably about 6.degree.. The depth and width of 
cam track 334 are selected so that cam track follower element 222 slides 
freely along the track (FIG. 5). 
Bolt group 54 is installed in receiver 12 for axial sliding movement 
between a forwardmost battery position (FIG. 3) and a rearward, recoil 
position (FIG. 6). This rearward, recoil position of bolt group 54 may, 
however, vary depending upon many factors including characteristics of the 
ammumition fired (which determine recoil forces), temperature of gun 10, 
amount of wear of the moving parts of the gun, and the amount of 
lubrication and dirt present in the gun. Guides, such as guides 338, 340 
and 342 (FIG. 2) on bolt carrier assembly 268 and mating, longitudinal 
guideways (not shown) along the inside of receiver 12 guide the 
reciprocating movement of bolt group 54 in the receiver. 
Formed through a righthand side wall 348 of receiver 12, opposite cam 
follower member 200 (FIGS. 2 and 5) is an axially elongate shell casing 
ejection port 350. Below and rearwardly of ejection port 350 is an axially 
elongate charger slot 352 through which, upon assembly of gun 10, a 
charging lever (not shown) outwardly projects. An axially elongated cam 
follower slot 354 is formed in a lefthand side wall 356 of receiver 12 to 
enable the insertion of cam follower arm 220 though such side wall and 
into engagement with bolt carrier cam track 334. Furthermore, receiver 12 
is open at the top in the region of belt feeding adapter assembly 40 (FIG. 
2). 
ASSEMBLY 
The assembly of gun 10 for firing shells 34 from ammunition belt 32 is 
generally apparent from the above description. By way of brief summary, 
however, bolt group 54 is installed in receiver 12 and barrel 14 is 
inserted in receiver forward region 168 (FIGS. 2 and 3). Barrel lock 
assembly 148 is assembled as described above and is pivotally mounted to 
receiver boss 140 by bushing 154 (FIGS. 2 and 3). Barrel 14 is then locked 
to receiver 12 by locking pin 152. 
Cam follower assembly 46, with cam follower arm 220 inserted inwardly 
through cam follower slot 354 (FIG. 5) in receiver side wall 356 and with 
cam follower element 222 in bolt carrier cam track 334, is pivotally 
mounted to receiver lugs 214 by pin 212 (FIG. 2). Belt feeding adapter 
cover assembly 60 is also assembled as described above with respect to 
FIG. 2 and, together with adapter base 56, is pivotally mounted, by pin 
112, to receiver boss 140 and side ears 142 (straddling barrel lock 
assembly 148). Cover assembly 60 is then opened relative to base plate 56 
and one end of an ammunition belt 32 is inserted between the cover 
assembly and base, with an end shell 34 at base slot 114 (i.e., at shell 
pick up position 118). Cover assembly 60 is then closed so that latches 
104 snap into member 147 on receiver 12. 
OPERATION 
FIGS. 3-5 are different views of gun 10 showing the condition of the gun at 
the instant of firing, with both bolt assembly 266 and bolt carrier 
assembly 268 in a forwardmost, battery position and with cam follower 
assembly 46 pivoted to its outermost position, feed pawls 122 being 
thereby positioned relative to ammunition belt 32 for advancing the belt 
when the cam follower assembly is pivoted inwardly. In contrast, FIGS. 
6-8, which correspond to respective FIGS. 3-5, show the condition of the 
gun at the instant of full rearward recoil of bolt assembly 266 and 
carrier assembly 268 (after firing of the gun or upon charging the gun), 
with cam follower assembly 46 pivoted to its inwardmost position and with 
feed pawls 122 having advanced a shell 34 held in ammunition belt 32 into 
shell pick up position 118. 
As more particularly described below, FIG. 9 is a series of simplified 
diagrams which correspond to time lapse photographs, depicting, in 
simplified form, the positive shell casing ejection operation of gun 10. 
FIG. 9a starts at the instant in time corresponding to FIGS. 3-5 when bolt 
and carrier assemblies 266 and 268 are fully forward for firing a 
chambered shell 34 and cam follower member 200 is pivoted fully outward. 
FIG. 9e ends at the later instant in time corresponding to FIGS. 6-8 when 
the bolt and carrier assemblies are fully rearward in recoil and the cam 
follower member is pivoted fully inwardly, causing ejection of a casing 
34a (of shell 34) outwardly through ejection port 350 as a result of 
ejector tip 224 of cam follower member entering through ejector recess 275 
in bolt 270 and engaging a base 360 of the casing, the casing pivoting 
about a rearward edge 362 of ejection port 350 and out through the port. 
FIGS. 9b-9d depict the shell casing ejection operation at times 
intermediate those depicted by FIGS. 9a and 9e. 
More specifically, at the instant of firing depicted in FIGS. 3-5 and 9a, 
barrel gas is bled from barrel 14 and may be directed in a conventional 
manner to a forward face (not shown) of gas piston 290 which is connected 
to bolt carrier assembly 268. The gas acting on piston 290 starts 
recoiling carrier assembly 268 rearwardly, thereby causing, by action of 
camming pin 324 and slot 328, the rotational unlocking of bolt assembly 
266 locking ring 188 (FIG. 3). As cam followen element 222 in engagement 
with bolt carrier cam track 334, rearward recoil movement of carrier 
assembly 268 causes cam follower assembly 46 to pivot inwardly about pin 
212 (direction of arrow "A," FIG. 4). This inward pivoting of cam follower 
assembly 46 moves shell advancing pawls inwardly towards barrel bore axis 
296 (direction of arrow "B," FIG. 5). Continued rearward recoil movement 
of carrier assembly 268 pulls bolt assembly 266 along in recoil and causes 
cam follower assembly 46 to continue pivoting inwardly, therby causing 
pawls 122 to continue the advancing of an endmost shell 34 inwardly 
towards pickup position 118. 
As bolt carrier assembly 268 recoils, recoil spring 293 (FIGS. 2, 3 and 6) 
is compressed, thereby absorbing recoil energy from bolt group 54 and 
bringing the bolt group to a stop at a rearmost position when all the 
recoil energy has been absorbed. In this bolt group rearmost position, 
depicted in FIGS. 6-8, cam track 334 on bolt carrier 278 has caused cam 
follower assembly 46 to pivot fully inwardly and has thereby caused belt 
advancing pawls 122 to inwardly push a shell 34 in belt 32 into pick up 
position 118 in readiness to be picked up by bolt 270 as bolt group 54 is 
driven back forwardly in counterrecoil by spring 293. 
It can be understood from the foregoing operational description that the 
complete belt/shell advancing step is performed on the recoil stroke of 
bolt group 54, unlike some known automatic guns which require some 
counterrecoil movement of the bolt before the shell advancing step is 
completed. As a result, according to the present invention, it is assured 
that a shell 34 is waiting in pick up position 118 when bolt assembly 266 
starts forwardly and the possibility that the bolt will counterrecoil to 
the breech without a shell having been picked up is eliminated. 
After bolt assembly 266 has engaged a shell 34 in pick up position 118, 
continued counterrecoil of the bolt assembly strips the shell out of its 
belt link 36 and pushes the shell forwardly and downwardly through feed 
slot 114. Shell pusher portion 76 pushed downwardly on base end regions of 
shell 34 in pick up position 118, thereby preventing the shell from being 
underridden by bolt assembly 266 instead of being picked up thereby. As 
shell 34 is driven forwardly by bolt assembly 266 after pickup, shell 
pusher 64 urges the shell downwardly through feed slot 114. 
After a shell 34 in pick up position 118 has been stripped out of belt 32, 
the loose link 36 is pushed out of link ejection portion 124 the next time 
the belt is advanced by pawls 122. 
As bolt group 54 counterrecoils forwardly, carrier cam track 334 causes cam 
follower assembly 46 to pivot outwardly about pin 112, thereby moving belt 
advancing pawls 122 outwardly (direction of arrow "C," FIG. 8) so that 
belt 32 can be advanced another shell position when the bolt group next 
recoils. As belt advancing pawls 122 move outwardly in response to bolt 
group counterrecoil movement, the pawls retract as then move past (under) 
the shell 34 that they will push inwardly against in the belt advancing 
step. Anti-back up pawls 66 (FIGS. 2, 5 and 8) push inwardly on this same 
shell to prevent the outward movement of belt advancing pawls 122 from 
backing up ammunition belt 32. 
When bolt assembly 266 reaches the breech, carrier assembly 268 still has a 
short forward distance to travel. Such continued forward movement of bolt 
carrier assembly 268 first cams bolt assembly 266 through a partial 
rotation so that the bolt assembly is locked to breech ring 188 (FIG. 8) 
and then fires the chambered shell by inpacting it with the forward tip of 
firing pin 296. 
As depicted in FIG. 9, recoil movement of bolt carrier assembly 268 after 
firing also causes the contolled or positive ejection of fired shell 
casing 34a outwardly through casing ejection port 350 in a consistant and 
reliable manner from firing to firing. In this regard, it has been found 
that using conventional bolt mounted, spring-loaded ejectors, casing 
ejection is often erratic and dependent upon bolt recoil velocity which 
changes as a gun heats up. For example, when firing is initiated and the 
gun is cold, the firing rate tends to be slow and recoil velocity is 
relatively low. In this condition, casing ejection tends to be slow and 
the casing being ejected (with the extractor as a hinge point) tends to 
"wrap around" the rearward edge of the ejection port, with the center of 
gravity outside the port, and be ejected backwardly towards the gun 
operator. However, as the gun get hot and speeds up, the casing being 
ejected tends to hit the rearward edge of the ejection port with the 
center of gravity inside the port. When this occurs, the casing can spin 
back into the gun the cause jamming of the gun. However, with the present 
configuration of gun 10, casing ejection by cam follower member tip 224 
tends to be independent of gun operating speed. 
As shown in FIGS. 9a-9c, as cam track 334 moves rearwardly (i.e., as 
carrier assembly 268 recoils after firing), cam follower member 200 (part 
of cam follower assembly 46) pivots inwardly, as described above, moving 
ejection tip inwardly towards bore axis 296 and bolt 270. Casing 34a is 
extracted and held to the bolt face by bolt-mounted extractor 274. At a 
preestablished bolt recoil position (FIG. 9c) cam follower member 220 has 
pivoted inwardly to an extent that ejector tip 224 starts entering 
ejecting recess 275 at the forward end of bolt 270 opposite extractor 274. 
As bolt 270 continues recoiling (FIG. 9d), the bolt moves rearwardly of 
ejection tip 224, with the result that the ejection tip "pushes" the 
contacted edge region of the casing forwardly (relative to the bolt), 
causing casing 34a to start pivoting outwardly through ejection port 350. 
Additional recoil movement of bolt 270 (FIG. 9e) causes ejection tip 224 
to pivot casing 34a further out of ejection port 350, the casing being 
finally released by casing extractor 274 for complete ejection. 
Because casing ejection always occurs at the same relative position between 
bolt 270 and cam follower ejection tip 224, casing ejection is 
substantially independent of bolt speed and consistant, complete casing 
ejection is achieved. 
CLIP FEEDING OF GUN 10 
Ammunition feeding of gun 10 can, as mentioned above and as shown in FIG. 
1a, alternatively be by means of clip adapter assembly 48 which is 
configured to hold a conventional rifle clip 50, for example, an M-16 
rifle clip. Comprising clip adapter assembly 48 is a tubular member 370 
having a rectangular cross section sized to receive clip 50. Installed in 
a rearwardly projecting region of member is a conventional clip release 
assembly 372 of the type ordinarily used with clip 50--for example, an 
M-16 clip release assembly. Projecting forwardly form member 370 are two 
parallel, spaced apart attachment arms 374 (FIG. 2), which corresponds to 
arms 108 of cover assembly 58. Mounting apertures 376, corresponding to 
cover assembly apertures 110, are formed through arms 374 for receiving 
mounting pin 112. Extending sidewardly form rearward regions of member 370 
are opposing, spring-loaded latch members 378 which correspond to latch 
members 104 of cover assembly 58. 
To install clip adapter assembly 48 to gun 10, assuming belt feeding 
adapter assembly 40 is already installed on the gun, the belt feeding 
adapter is detached by releasing latches 104 removing mounting pin 112. 
Pawl assembly 202 is then removed from cam follower assembly 46 by 
removing C-ring 258 from pin 240. Clip adapter arms 374 are then inserted 
in slots 136 and pin 112 is replaced. Clip adapter assembly 48 is then 
pressed down so that latches engage latch member 147 on receiver 12. A 
loaded clip 50 is then snapped into member 370. 
Thereafter operation of gun with clip feeding is the same as described 
above for belt feeding, except that sheels are picked up directly from 
feedlips on clip 50 instead of from ammunition belt 32. Shell pick up 
position 118 is, however, the same in both cases. 
Although there is described above a specific arrangement of a convertible 
belt/clip-fed automatic gun, with positive shell casing ejection, in 
accordance with the present invention for the purpose of illustrating the 
manner in which the invention can be used to advantage, it is to be 
appreciated that the invention is not limited thereto. Accordingly, any 
and all variations and modifications which may occur to those skilled in 
the art are to be considered to be within the scope and spirit of the 
invention as defined by the appended claims.