US3009396A

US3009396A - Gas piston operated automatic gun

Info

Publication number: US3009396A
Application number: US775844A
Authority: US
Inventors: Paul H Dixon
Original assignee: United Shoe Machinery Corp
Current assignee: United Shoe Machinery Corp
Priority date: 1947-09-24
Filing date: 1947-09-24
Publication date: 1961-11-21
Anticipated expiration: 1978-11-21

Description

Nov. 21, 1961 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN '7 Sheets-Sheet 1 Filed Sept. 24, 1947 in V6 27 for PauZ ff. Dix-0n Nov. 21, 1961.

Filed Sept. 24, 1947 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN 7 Sheets-Sheet 2 Inventor Paul /7213211071 '7 Sheets-Sheet 3 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN Nov. 21, 1961 Filed Sept. 24. 1947 xvw g @N v w was In were Paul HDz'xorz Nov. 21, 1961 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN 7 Sheets-Sheet 4 Filed Sept. 24, 1947 'III 1 YIIIIIIIII in we n Mr Paul H. Dixon '7 Sheets-Sheet 5 In ventor" Paul H. Dix-0n Nov. 21, 1961 P. H. DIXON GAS PISTON OPERATED AUTOMATIC GUN Filed Sept. 24, 1947 Nov. 21, 1961 P. H. DIXON PISTON OPERATED AUTOMATIC GUN GAS 7 Sheets-Sheet 6 Filed Sept. 24, 1947 Inventor FauZHDz'won Nov. 21, 1961 P. H. DIXON 3,009,396

GAS PISTON OPERATED AUTOMATIC GUN Filed Sept. 24, 1947 '7 Sheets-Sheet '7 in venzm Paul fiDz'x'on B hi 0 United States Patent 3,009,396 GAS PISTON OPERATED AUTOMATIC GUN Paul H. Dixon, Rockford, 111., assignor to United Shoe Machinery Corporation, Flemington, N.J., a corporation of New Jersey I Filed Sept. 24, 1947, Ser. No. 775,844 1 Claim. (Cl. 89-191) This invention relates to ordnance and is herein illustrated as embodied in an automatic 20 mm. gun or. cannon which will operate effectively at a very high cyclic rate and is especially useful in airplanes.

The present invention consists in the novel features hereinafter described, reference being had to the accompanying drawings illustrating one embodiment of the invention which is fully disclosed in the following description and claim.

In the accompanying drawings,

FIG. 1 is a plan view of the rear portion of the illustrative gun;

FIG. 2 is a vertical section on line II-II of FIG. 1; a bolt assembly of the gun being shown in its battery position ready for the firing of the gun;

FIG. 3 is a vertical section on a forward extension of line II-II of FIG. 1 showing a recuperator of the gun;

FIG. 4 is a horizontal section on line IVIV of FIG. 2;

FIG. 5 is a view similar to FIG. 2 showing the gun after it has been fired and the bolt assembly has been moved to its fully recoiled position;

FIG. 6 is a section on line VI--VI of FIG. 4 illustrating cartridge feeding and electric ignition mechanism of the gun;

FIG. 7 is a section on line VII-VII of FIG. 4 showing a reaction unit of the gun;

FIG. 8 is a section on line VIII--VIII of FIG. 2;

FIG. 9 is a perspective view partly in section on line IXIX of FIG. 2 showing the forward end of a bolt and a feed box of the gun;

FIG. 10 is a section on line X-X of FIG. 2;

FIG. 11 is an enlarged vertical central section of portions of the bolt and a slider of the bolt assembly;

FIG. 12 shows in perspective -a gas operated piston forming part of an ammunition feeder of the gun;

FIG. 13 is a section on line XIIIX[II of FIG. 10;

FIG. 14 shows in perspective the bolt assembly and a bolt lock which may be secured to and forms in effect part of the receiver of the gun;

FIG. 15 is an exploded view of the bolt assembly illustrated in FIG. 14;

FIG. 16 shows in perspective the bolt and portions of the slider and a wedge forming part of the bolt assembly; the bolt being in a locked battery position in front of portions of the lock;

FIG. 17 is a perspective view illustrating portions of bolt assembly guides or rails of the receiver and cartridge case deflecting cams formed on said rails;

FIG. 18 is an exploded view showing portions of a cradle and a recuperator, which cooperate to support the gun for sliding movement in recoil and counter-recoil, and also showing a bracket for locking the gun in operative position in the cradle and the recuperator; and

FIG. 19 is a section on line XIXXIX of FIG. 3.

The illustrative gun is mounted in a cradle 40 which may be secured to a turret (not shown) of an airplane for example, said gun being movable in recoil and counter- 3,009,396 Patented Nov. 21, 1961 through mechanism hereinafter described, to the cradle, and a recoil spring nut '48 (FIG. 3) which is threaded onto a barrel 50 of the gun and may be considered as part of the barrel.

The barrel 50 is threaded into a receiver 52 and is properly positioned lengthwise in and secured to the receiver by a screw 54 (FIGS. 2, 4 and 5) which is threaded into the receiver and fits in a recess 56 in the barrel. The gun is provided with a breechblock or a bolt 58 having a rear T-shaped tongue or projection 60 (FIGS. 4, 14, 15 and 16) fitting in a complemental vertical or transversely extending guideway 62 at the forward end of a slider 64, said bolt and, slider which, together with a wedge 66, may be referred to as a bolt assembly, being guided for movement in recoil and counter-recoil by longitudinally extending rails or guides 68 (FIGS. 2, 4, 5, 6, 7 and 17), faces 70 (FIGS. 4, 6 and 7), 72 (FIGS. 2,5,6 and 7) of the receiver 52 and faces 70a, 72a (FIGS. 8, 9 and 14) of bolt locks 82. As will be explained later, the rails '68 are formed in part by forward extensions 74 of a drum 76 of a reaction unit 78 and by abutments or rail portions 80 (FIGS. 4, l4 and 16) of the bolt locks 82 which fit in complementally shaped recesses 84 (FIGS. 4, 5, 8 and 9) of the receiver 52 and each of which is secured to said receiver by a nut and screw 86 (FIGS. 4, 5 and 6) and may be considered as part of the receiver. The major portion of an inside face 88 of the cradle 40 is cylindrical and forms a guideway with which cylindrical outside faces 90 (-FIGS 1, 2, 4, 5 and 7) of the receiver slidingly engage, upwardly and downwardly disposed projections 92 (FIGS. 1, 2, 5 and 10), 94 (FIGS. 2, 5, 6, 7, 8 and 10) of the receiver engaging in guideways 96 (FIGS. 1 and 10), 98 (FIG. 10) formed by spaced pairs of

flanges

100, 102 formed in the cradle.

The slider 64 has a depending lug 104 (FIGS. 2, 5, 6, 7, 14 and 15) provided with a recess 106 for receiving the rear end of a spring 108 fitting into a recess 110 of a shank 112 of the wedge 66. The wedge 66 has a T- shaped guideway 114 (FIGS. 2, 5, 9 and 15) extending longitudinally and transversely of the receiver for receiving a T-shaped projection 116 (FIGS. 9 and 15) at the lower end of the bolt 58, the depending lug 104 of the slider being provided with a pair of guideways 118 (FIGS. 6, 7, l4 and 15) for receiving bifurcations of the shank 112 of the wedge 66. The wedge 66 is moved rearward, by mechanism hereinafter described, upon the slider 64 until faces 120 (FIGS. 9, 14, 15 and 16) of the bolt 58 engage faces 72a (FIGS. 8, 9 and 14) of the bolt lock 82, at which time channels 124 of the bolt are in register with rail engaging channels 126 respectively of the slider 64, the bolt, which is then in its lowered or forward unlocked position, thereafter being moved, together with the slider and the wedge 66 in recoil along the rails 68, which may be described as including the abutments 80 (FIGS. 4, l4 and 16) of the bolt lock 82, rearward or in recoil without substantial resistance and thereafter against the action of the reaction unit 78 to their fully recoiled position shown in FIG. 5.

As above explained, the rails 68 are formed in part by the rail portions 74 (FIGS. 2, 4, 5 and 7) of the drum 76 which forms part of the reaction unit 78, said rail recoil in the cradle approximately one-quarter of an.

housing assembly 46 (FIGS. 3, 18 and 19) secured,

portions fitting in slots 128 of the receiver 52 in alinement with the portions of the rails formed integral with the receiver. The lateral bearing faces 70 of the receiver 52 extend from the bolt lock 82 to the reaction unit 78 and are engaged by the opposite faces 130 (FIGS. 4, 14, 15 and 16), 132 of the slider and the bolt to assist in guiding these'members in recoil and counter-recoil in the receiver 52. The reaction unit housing portion 134 (FIGS. 2, 4, 5 and 7) of the receiver 52 is cylindrical and accordingly the portions 74 of the rails 68 extending into said reaction unit housing portion engage the bottoms of the

channels

126, 124 of the slider 64 and the bolt' 58 effectively to guide these members without the assistance of the lateral bearing faces 70 of the receiver;

The bolt 58 is moved to, and is held in, its raised battery position shown in FIG. 2 by the wedge 66, the construction and arrangement being such that when the bolt is in it's lowered unlocked position in engagement with the rear end of the barrel 50 after chambering a cartridge 136 (FIGS. 1, 2 and 5), the wedge 66 under its own momentum and assisted by the spring 108, is moved forward causing the bolt to be raised to its battery position, rear faces 138 (FIGS. 14, 15' and 16) of the bolt then being in front of and in engagement with front faces of the abutrnents 80 and flanges 142 of the bolt lock- 82 to lock the bolt 58 and accordingly the bolt assembly against recoil movement. The slider 64 may be said to be slidingly coupled to or interlocked with the bolt 60* and the wedge 66.

After the gun has been fired the bolt 58 is lowered from its raised battery position, to unlock it, by rearward movement of the wedge 66 acted upon by a piston 144 (FIGS. 2, 5, 8, 9 and which is slida'ble in a cylindrical recess 146 formed in the downwardly projecting portion 94 of the receiver 52 and acts against the front face of the wedge 66. It will be noted that the bottom of the bolt 58 has formed in it a tunnel 148 (FIGS. 2, 5 and 9) to permit rearward movement of the piston 144 without interfering with the free lowering of the bolt. The piston 144 has a shank portion of reduced diameter, an expansion chamber 150 (FIGS. 2, 5 and 10) being formed between the cylindrical recess 146 and the shank portion of the piston. Between the chamber 150 and a bore 152 of the barrel 50 is a gas passage 154 (FIGS. 2 and 5) formed in part by a restricted orifice in a silver heat dissipating plug 156 housed in a recess 158 of the barrel.

When the gun is fired the receiver 52, together with l the various gun parts supported by it, moves approximate ly one-quarter of an'inch in recoil along the inside faces 88- of the cradle 40 against the action of the recuperator 44 (FIGS. 3 and S) and then moves back to battery position under the action of said recuperator. In the meantime, high pressure expanding gases from the. bore 152 of the barrel 50 pass through the passage 154 into the chamber 150 forcing the piston rod 144 with considerable pressure against the front face of the wedge 66. When the gun is first fired the rearward force of the explosion against acase 160 of the expended cartridge 136 forces the bolt 58 against front faces of the abutments 80' and the flanges 142 of the bolt lock 82 with so much force that the piston 144 acting through the wedge 66 does not have sufiicient power to move the bolt to its lowered unlocked position. When the receiver 52 is near the end of its recoil movement the pressure in the bore 152 of the barrel 50 will have been reduced sufficiently to insure against gases entering the receiver and rearward pressure of the piston 144 acted upon by the expanding gases in the chamber 150 moves the wedge 66 rearward against the action of the spring 108 to a rearward position upon the slider 64 and thus draws the bolt 58 downward until the faces 120 (FIGS. 9, 14, and 16) of the bolt'58 engage the faces 72a of the bolt lock 82of the receiver 64, at-which time the grooves or channels 124 of the bolt are in register with the abutments 80 of the bolt lock 82. The bolt 58, the slider 64 and the wedge 66 guided by the rails 68 and the lateral bearing faces 70 of the receiver 52 are then moved in recoil under the action of the gas actuated piston 144 with the assistance of the blow-back action of the case of the expended cartridge 136 against the bolt. As explained in application for United States Letters Patent Serial No. 716,469, filed December '16, 1946 in my name, it is sometimes desirable to insure against any unburned gases entering the receiver '52,- in which event the gas passage 154 is restricted sufficiently to delay wedge actuating movement of the piston until a 4 substantially all the unburned gases have left the bore 152 of the barrel 50.

The reaction unit 78 comprises a recessed plate '162 (FIGS. 2, 4, 5 and 7) which fits slidingly in the housing portion 134 of the receiver 52 and is normally forced against a transverse shoulder 164 of the receiver by a spring 166. The spring 166 is initially compressed by the retaining. drum 76 held in the housing portion 134 of the receiver 52 by a threaded rear cover 168 (FIGS. 2, 4 and 5) which is screwed into the rear end of the receiver and is locked in'its operative position in said receiver by a spring-pressed plunger 170 (FIGS. 2 and 5) slidingly mounted in the cover and constructed and arranged to enter a hole 172 of the receiver. As the bolt assembly is moved in recoil, opposite faces 174 (FIGS. 14, 15 and 16) of the slider 64 and opposite faces 176 of the wedge 66 engage the plate 162, the spring 166 being compressed to absorb the energy of the bolt assembly and .to effect movement of said assembly in counter-recoil.

Cartridges 136 assembled in a belt 177 (FIGS. 1 and 6) are automatically fed successively into a centralized ram ming position shown in FIG. 5 (dash line position FIG. 6) in the receiver 52 of the gun, by an ammunition feeder 178 (FIGS. 1, 6 and 9) such as is fully disclosed in an application for United States Letters Patent Serial No. 764,790, filed July 30, 1947 in my name. Cartridges 136 in the belt 177 are fed down through a chute 180 to a carrier or sprocket 182 rotatably mounted in a feed box 184 which has at its forward end a pair of lugs 186 (FIGS. 7 and 9) constructed and arranged to fit in channels 188 of the cradle 40 and which has rearwardly extending arms 190 (FIGS. 1, 2, 5 and 7) spaced to include between them an upstanding boss 1-92 of the cradle, said arms being.

to accommodate clips 202 (FIGS. 1 and 6) of the cartridgebelt 177 and which have outwardly curved-forward ends 204 (FIGS, 1, 2 and 5) constructed and arranged to cooperate with a rammer 206 hereinafter described and. formed integral with the bolt 58 for chambering the cartridge. The sprocket 182 is tion at the cyclic rate of the gun by a worm 208 (FIGS. 1, 2, 5, 8' and 9) mounted upon a piston210 which is reciprocable but not rotatable in a cylinder 212 (FIGS. 2, 5, 10 and 13) formed in part by a sleeve214 secured to the receiver 52, and which is operated by expanding gases admitted to an intermediate bore 216 (FIGS. 2, 5 and '13) of the sleeve through a passage 21 8 extending through the barrel 50, the receiverv 52 and the sleeve'212. The p'assag'e'218 is formed in part by a restricted bore or passage 220 through a silver plug 222 housed in a pocket of the barrel.

In' splined .relation with the sprocket 182 and held against'a shoulder of said sprocket by a pair of spring- .pressed locking arms 219 (FIGS. 1, 2, 5 and 9) is a nut 223 (FIGS. 2, 5 and 8) having internal spiral threads meshing withex'ternal spiral threads of the. worm 208 which, as will be hereinafter explained, during rearward 'movement'of the piston 2 10 under the action of expanding gas pressure in the sleeve 214, is secured against rotation on the piston.

The piston 210 is secured against rotation in the sleeve 214 by a plurality of longitudinal channels 224 (FIGS. 5 and 13) forming part of the sleeve and shaped and arrangedto receive slidingly longitudinal flanges 226 (FIGS. 2, 5, 12 and 13) formed in the piston. The gun parts are in 'their positions shown in "FIG. 2 when the initial round of a burstof cartridges 136 is fired, expanding gases -in the bore 152 of the barrel 50 thereafter traveling through the

passages

218, 220 into the intermediate bore 216 ofthe sleeve .214 and around a flange 228 of the piston 210 into a-large bore 230 (FIGS. 2, 3,5, 10 and 13) of the sleeve. The forward end of the sleeve 214 is closed rotated step by step in timed relaby a plug 232 (FIGS. 1, 2, 3, and which is forced into said sleeve by a collar 234 carried by the barrel 50 and backed up by a flange on said barrel, the plug being inserted in the bore 230 of the sleeve 214 at the time that the barrel is threaded into the receiver 52. When the piston 210 is in the position illustrated in FIGS. 2 and 13 high pressure gases admitted to the intermediate and large bores 2116, 230 of the sleeve 214, which bores at that time are in'communication, cause rearward movement of the piston by reason of unbalanced gas pressure against opposed faces 236, 238 of the flange 228 of the piston and a face 239 (FIGS. 2, 5, 12 and 13) at the forward end of the longitudinally flanged portion 226 of said piston with the result that four recesses 240 (FIGS. 2 and 5) (only one shown) in the piston move into interlocking relation with opposed studs 242 at the forward end of the worm 208, then in its forward position shown in FIG. 2. The piston 210 thereafter causes the worm 208 to slide rearward with it until the rear end of said worm engages a transverse face 244 (FIGS. 2 and 5) of an axially extending bore 246 in the sprocket 182, movement of the piston being resisted by a spring 248 housed in the bore and having its forward end in engagement with a collar 250 secured to the piston.

Rearward movement'of the Worm 208 in meshing engagement with the nut 223 and interlocked against rotation upon the piston 210 will effect clockwise rotation of the sprocket 182, as viewed in FIG. 6, causing the leading cartridge 136 in the belt 177 to be forced against the slider 64 and the bolt 58, which at that time are moving in recoil and are in such positions as to prevent the cartridge from being moved to its central or ramming position shown in FIG. 5 (dash line position as shown in FIG. 6) in the receiver 52. After the bolt.58 has moved to a recoil position rearward of and out of engagement with the leading cartridge 136 in the belt 177, the piston 210 is moved further rearward by the expanding gases until the worm 208 engages the face 244 of the bore 246 in the sprocket 182 at which time said leading cartridge in the belt is in its central or ramming position and the sprocket may be said to be in its indexed position. The sprocket 182 is held in its indexed position by a spring-pressed plunger 249 (FIGS. 1 and 8) which is slidingly mounted in a guideway 251 of the feed box 184 and has its lower end in engagement with one of four recesses 253 (FIG. 8) in the nut 223.

When the bolt 58 is in battery position the rear end of the cartridge 136, as illustrated in FIG. 2, is in engagement with a vertical face 254 (FIGS. 2, 4, 5 and 9) of a recess 256 (FIG. 9) in the forward end of the bolt which has ramming faces 258 and slots 260. After the gun has been fired and the bolt 58 has been moved to its lowered unlocked position ready to be moved in recoil together with the slider 64, the upper edge of the rim 262 of the case 160 of the spent cartridge 136 is in the slots 260 with the result that said case, upon recoil movement of the bolt, is extracted from a cartridge chamber 264 of the bore 152 of the barrel 50. As the case 160 of the spent cartridge 136 is extracted from the cartridge chamber 264, the upper edge of its rear end engages cam surfaces 266 (FIGS. 5 and 17) of the rails 68 causing said case to be deflected downward through alined openings 268, 270 (FIGS. 2, 5, 6 and 9) formed in the receiver 52 and the cradle 40 respectively. The bolt 58 may be said to comprise the rammer or spaced arms 206 which extend or project forwardly from the upper lateral portions of the vertical face 254 and have undercut opposing faces, the slots 260 being formed in said arms and having their rear faces continuous with said vertical face.

As the bolt assembly is moved forward in counterrecoil the faces 258 of the rammer 206 engage the rear end of the cartridge 136 then in the belt 177 and in ramming position, causing the forward end of said cartridge to be moved forward and deflected downward out of its associated cartridge clip 202 of the belt by reason of the cooperative action of the forward portion 204 of the pocket 196 of the sprocket 182 and the cartridge clasping clip 202 of the belt. As soon as the cartridge 136 leaves the belt 177 its rear and drops below the faces 258 of the rammer 206 and is engaged by the vertical face 254 of the bolt 58, continued forward movement of the bolt causing the cartridge to be chambered, the rim 262 during the chambering action being raised into the slots 260 in the bolt. As soon as the bolt 58 engages the rear end of the barrel 50 the wedge 66 under its own momentum and actuated by the spring 248 moves forward to its battery position shown in FIGS. 2 and 16 causing the bolt 58 to be raised to its locked battery position in which the rear faces 138 of the bolt are locked in front of the flanges 142 and the abutments of the bolt lock 82.

The cartridge 136 is fired electrically by an electrode or firing pin 272 (FIGS. 2, 4, 5, 9, 11 and 15) which is mounted for sliding movement in an insulating sleeve 274 secured to the bolt 58 and has fixed to it a collar 276 (FIGS. 11 and 15) the electrode being constantly urged rearward with relation to the bolt by a spring disk washer 278, the forward end of the electrode at the time the bolt is unlocked being positioned just behind the face 254 of the bolt. Secured to the collar 276 of the electrode 272 is an insulating disk 280 which by the action of the spring disk washer 278 is forced against and slides along a face 282 (FIG. 11) of the slider, which face constitutes a stop, as the bolt 58 is raised to and lowered from its locked battery position.

When the bolt 58 is in its locked battery position shown in FIGS. 2 and 11 the rear end of the electrode 272 is in engagement with an inclined forward surface 284 (FIG. 11) of a rod or conductor 286 (FIGS. 2, 4, 6, 11 and 16) positioned in a longitudinal recess 288 (FIGS. 4, 5 and 11) of the slider 64 and mounted for longitudinal sliding movement in insulating blocks 290, 292 (FIG. 11) secured to the slider. The rod 286 is constantly urged to the right as viewed in FIG. 11 to a position in which a flange 294 of the rod is substantially in engagement with the insulating block 290, by a spring 296 (FIGS. 2, 11 and 16) which encircles the rod and the forward and rear ends of which the flange 294 and a spacer block 298 (FIGS. 2, 5 and 11) carried by the rod. Secured to the rod 286 and arranged between the spacer block 298 and the insulating block 292 is a conductor 300. The rod 286, together with the parts mounted on it, is inserted in its proper position in the slider, the insulating block 292 being pressed forward into position in the slider and held in such position by a snap spring 302 (FIGS. 7, ll, 14 and 15). During the forward end of the counter-recoil movement of the slider 64 the conductor 300 engages a flexible leaf spring 304 (FIGS. 4 and 6) which is mounted in an insulating tube 306 secured to the receiver 52 and is in sliding engagement with a leaf spring conductor 308 secured to a screw 310 fixed to the cradle 40, current being supplied to the screw by a cable 312 leading to a source of power. As the slider 64 moves forward in counter-recoil the conductor 300 engages the energized leaf spring 304 and as the bolt 58 is raised to its battery position the rear end of the electrode 272 carried by the bolt engages the front face 284 of the spring-pressed rod 286 which moves the collar 276 of the electrode 272 to the right (FIG. 11) against the action of the spring washer 278 thereby causing the forward end of said electrode to project slightly beyond the face 254 of the bolt 58 in order to contact the rear end of the chambered cartridge 136 to fire said cartridge.

Guns of airplanes are commonly overhauled after each mission, and accordingly, it is desirable that burned out guns be quickly removed from their cradles 40 and overhauled guns be substituted therefor. With the foregoing consideration in view, a cylindrical spring housing 314 (FIGS. 2, 3, 5, l8 and 19) forming part of the recuperator 44 has formed integral with it a pair of laterally extending flanges 316 (FIGS. 18 and, 19) ,which are con-r struct'ed and arranged to fit in arcuate slots 318 formed in the cradle 40. Before removing the burned out gun from the cradle the feed' box 184 is removed. from-the cradle by removing the pin 194 and lifting said box from the cradle. After removing a locking bracket 320 (FIGS. 3, 18 and 19), which will be described later, from its locking position on the gun the spring housing 3.1.4 is rotateed 90 until its flanges 316 are in dash-line position shown in FIG.. 18, the receiver then being slid forward outthrough the front of'the cradle 40.

In mounting a reconditioned gun in the cradle, the receiver of the gun is slid rearward into the cradle and the spring housing 314 is then rotated causing its flanges 316 to. engage in the arcuate grooves 318 of the cradle, said housing thus being secured against lengthwise movement in the cradle. To insure against displacement of the spring housing 314 thus positioned in the cradle 40 there is provided the above-mentioned locking bracket 320 (FIGS. 3, 18 and 19) which has a circular portion 322 constructed and arranged to fit slidingly on the spring housing 314 and which, when arranged in itslocking position, has upper and lower plates 324, 326vthereof in enaggement with upper and lower surfaces 328, 330' respectively of the cradle, inturned ends of arms 332 extending forward from the circular portion 322 fitting in slots 334 of the spring housing, and four rearwardly extending lugs 336 fitting in grooves 338 respectively of the cradle 40, the construction and arrangement being such that the spring housing is held against rotation on the cradle. It will thus be apparent that the guns may be quickly and effectively removed from and assembled in the cradle. 7

Having thus described my invention what I claim as new and desire to secure by Letters Patent of the United States is:

An automatic gun comprising a barrel, a receiver which is secured to the barrel and has longitudinal guides, a bolt lock having abutments which are in alinement with said guides, a slider movable longitudinally of the 8. receiver in recoil and counter-recoil upon said guides and said abutments, a bolt which is coupled for longitudinal movement with the slider and is slidableheightwiseof the receiver with relation to the slider, said bolt having;

at its lower end a projection extending longitudinally and heightwise of the receiver, a wedg'eymounted for longitudinal movement upon the slider and having a guideway which extends longitudinally and heightwise of the receiver and is constructed and arranged slidingly to receive the projection of the bolt, a stop carried. by the receiver, and a gas operated piston movable a short distance in recoil under the action'of high pressure expanding gases. between a battery position adjacent to the Wedge and a rest position against the stop, said piston during movement from its battery to its rest position being adapted to move the wedge rearward upon the slider thereby eifecting heightwise movement of the bolt upon the slider from a raised locked position in front of the abutments of the bolt lock to a lowered unlocked'position and then to impart to the wedge sufficient energy to move the wedge together with the slider and the bolt as a unit a substantial distance in recoil.

References Cited in thefile of this patent UNITED STATES PATENTS.

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