MULTI-BARREL MACHINE GUN

Abstract: A multi-barrel machine gun has a body (11), an assembly of barrels (17), parallel to and equidistant from an axis of rotation, extending forwards from a carrier (18) rotatable in the body (11), the barrels (17) passing through a rotor (22) within an eccentric stator (23) connected to the body (11) by a torque tube (13), vanes dividing the space between rotor (22) and stator (23) into compartments (25) into each of which a gas port (26) leads from a barrel (17). A bolt slide assembly (34) behind and rotatable with the carrier (18) holds slidable bolts (37), each aligned with a barrel (17) containing a spring-loaded firing pin (42) and having means for taking a cartridge from a magazine (50). Cam followers (40) on the bolts (37) and on the firing pin (42) engage a bolt cam track (41) and a firing pin cam track (45) respectively within the body (11) to advance the bolts (37) in sequence to insert cartridges to barrels (17) at the firing position, and to drive the associated firing pins (42) to fire the cartridges, gas from the spent cartridges driving the rotor (22) to rotate the assembly of barrels (17), carrier (18) and bolt slide assembly (34).

Description: Title: "MULTI-BARREL MACHINE GUN" BACKGROUND OF THE INVENTION (1 ) Field of the Invention This invention relates to a multi-barrel machine gun. (2) Prior Art The feeding and firing mechanisms limit the rate of fire of a conventional machine gun or other automatic firearm and the wear generated in the com- ponents may cause the machine gun or firearm to jam. In addition, cartridge feed belts are difficult to change quickly, while conventional magazines have only a small capacity. Furthermore, the barrel quickly becomes hot and undergoes rapid wear when continuous bursts are fired necessitating requiring frequent barrel changes. In an effort to overcome these problems, General Electric Corporation of the U.S.A. has developed a six barrel "mini-gun", which has a much higher rate of fire of up to 6000 rounds per minute. However, this gun is heavy and not easily portable and so is usually mounted, for example in helicopters or flying gunships for infantry support. In addition, the gun requires a power supply and so is not self-contained. SUMMARY OF THE PRESENT INVENTION It is the general object of the present invention to provide a multi-barrel machine gun for automatic firearm which is self-contained, and can have a very high rate of fire in a continuous firing mode. The gun preferably may be set to fire only single shots or short bursts. Other objects which may be achieved in preferr¬ ed embodiments of the invention are to provide such a gun with an easily variable rate of fire in which the barrels have a long life and so retain their accuracy, and which can be easily dismantled and reassembled for servicing in the field. The invention resides broadly in a multi-barrel machine gun including: a gun body, assembly of parallel gun barrels mounted on the body equidistantly from a longitudinal axis of rotation, drive means to rotate the barrels to bring them in sequence to a firing position, bolt means in the body to feed a cartridge to each barrel brought to firing position; and firing means to fire the cartridges; the drive means being powered by expanding gas from the spent cartridges. Preferably the receiver body is fitted with a pistol grip and/or stock and a trigger mechanism. Preferably a housing or torque tube is provide about the barrels, the housing or tube being preferably removable from the body to enable the barrels to be removed for maintenance. Preferably the drive means includes a rotor fixed about the barrels within a stator eccentric to the axis of rotation of the barrels, the cavity between rotor and stator being divided into a plurality of chambers by sliding vanes, gas ports connecting the barrels to the chambers, high pressure gas from fired cartridges acting on the vanes to rotate the rotor and barrels. Preferably valve means are provided on an exhaust port from the stator, the firing rate being con¬ trolled by the effective size of the exhaust port as set by the valve means. In a second preferred embodiment, the drive means hereinbefore described may be provided adjacent the body of the gun. Preferably a barrel carrier about the rear of the barrels is rotatably mounted in the body and has a bolt slide track for each barrel, a bolt assembly being slidable in each slide track to feed a cartridge to its respective barrel, each bolt assembly being moved in its slide track by a cam follower on the bolt assembly which follows a cam track in the body, each bolt having a firing pin with a follower for a second cam track in the body, the firing pin being advanced relative to the bolt assembly to fire the cartridge. Preferably a safety lock prevents the firing pin from firing the bullet when not required. A cocking knob may be provided to rotate the barrel assembly to bring a barrel to the firing position when a magazine has been changed. A bolt stop may be provided on the gun's trigger to stop rotation of the barrel assembly, and so stop the gun firing, when the trigger is released. Preferably a pair of hooks adjacent a spent case extraction port in the body extend into circumferent ial slots in the barrel assembly to extract the spent cartridge cases, similar hooks being provided on the magazine to present the cartridges to the bolt assemblies for feeding to the barrels. BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood a preferred embodiment will now be described with referenc to the accompanying drawings, in which:- FIG. 1 is a partly broken-away perspective vie of an assembled machine gun according to the invention; FIG. 2 is a perspective view of a magazine of the gun; FIG. 3 shows in perspective the forward end of the gun; FIG. 4 is a sectional view taken on line -"4 in FIG. 3; FIG. 5 is a sectional view taken on line 5-5 in FIG. 1 ; FIG. 6 is a partly sectioned view of the gun body; and FIG. 7 is a perspective view of a bolt and firing pin assembly. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The machine gun shown in the drawings has a substantially tubular body 11 which has an externally screwthreaded cylindrical portion 12 at its front. A torque tube 13, with cooling holes 14, has a rear peripheral flange 15 which is butted against the front face 12a of the screwthreaded portion 12, a pin (not shown) on the flange engaging in a hole 12b in the front face, the torque tube being secured to the body 11 by a knurled nut 16. Four barrels 17, e.g. of NATO 5.56mm. (0.223 inch) calibre, are equally spaced about a longitudinal axis of rotation and are secured together adjacent their rearward ends by a cylindrical block or carrier 18 which is rotatable in the bore 19 of the screwthreaded portion 12 and has a reduced diameter front part 20 rotatable within the rear part of the bore 21 of the torque tube 13- A rotor 22 surrounding the barrels 17 near their front ends is rotatable within an eccentric stator 23 within the front part of the torque tube 13. Spring- loaded radial vanes 24 in the rotor engage the stator to divide the cavity between rotor and stator into four chambers 25 of differing volumes. A gas outlet port 26 connects the bore of each barrel 17 to a respective chamber. A block 27 fitted to the top of the stator 23 has an internal exhaust port 28 in communication with the uppermost one of the chambers 24. A firing rate control valve 29 has a divergent slot 30 which selectively communicates with the exhaust port 28 to vary its effective area. As shown in FIG. 3, the block 27 is slidably received in a T-shaped slot 31 to enable it, with its control valve, to be removed for repair or replacement. A pistol grip 32 is removably engaged, at its top, in a T-section slot 33 on the torque tube 13 below the stator 23. A bolt track assembly 3 (see FIG.5 ) at the rear end of the assembly of barrels 17 and carrier 18 is rotatable mounted in the rear or main part 35 of the bore of the body 11. Four equally spaced T-shaped bolt slide tracks 36 are formed in the bolt track assem- bly 34 in alignment with the barrels 17 and a bolt 37 (see FIG.7 ) is slidable in each of the bolt slide tracks. A recess 38 is formed in the front of the body 39 of the bolt to receive and engage the cap of a cartridge case. A bolt cam follower 40 having a planar or shallow curved rear face extends from the bolt and engages a first cam track 41 formed in the bore 35 of the body 11. A firing pin 42 is slidable in the bolt 37 and urged forwardly by a compression spring 43- The firing pin, which can enter the bolt recess 38 to fire a cartridge, has extending from it a firing pin cam follower 44 engaged with a second or firing cam track 45 also formed in the bore 35 of the body 11. A pair of circumferential grooves 46 are formed around the bolt track assembly 34. A substant¬ ially radial abutment face 47 extends out from the assembly, upstream of each bolt slide track 36, between the circumferential grooves 46, the rear face 48 of the abutment being inwardly curved. The abutment face 47 is adapted to engage a cartridge held against a pair of induction lugs 49 on the gun magazine 50, which is releasably engageable with the underside of the body 11 , the lugs 49 being received within the circumferent¬ ial grooves 46. A coiled spring (not shown) of known type within the magazine urges the contained cartridges in sequence through a discharge outlet 51 and into engag¬ ement with the lugs 49. A spent case extraction port 52 in the right hand side of the body 11 has a pair of extraction lugs 53 which are also received in the circum- ferential grooves 46 about the bolt track assembly. An assembly of pistol grip 54 and trigger 56 is slidably engaged in a T-section slot 55 in the under¬ side of the body 11. A Y-shaped yoke 57 is fitted on the shaft 58 of the trigger and has a fixed bolt stop 59 and a springloaded bolt stop 60. A lever 61 on the end of the trigger shaft 58 is connected to a second lever 62 by a lost-motion spring connector 63. The lever 62 is fixed on one end of a shaft 64 in a removably safety catch block 65 received in a tran verse T-section slot 66 in the upper part of the body 11. A primary cam 67 fixed on the shaft is movable from a firs position which enables the firing pin cam follower 44 to follow the firing cam track 45 to fire a cartridge, to a second position, where it directs the firing pin cam follower 44 along a safety track (not shown) where the cartridge cannot be fired. A safety catch 68 is rotatably mounted in the safety catch block 65 and is provided with an eccentric plate 69 which can enter a slot (not shown) in the shaft 64 to prevent the latter from rotating and so prevent the gun from being fired. A secondary cam 70 on the shaft 64 is provided with a ratchet panel (not shown) which allows the firing pin cam follower 44 to move from the safety track to the firing cam track 45 when the trigger is depressed. A plate 71 engaged in a circumferential groove 72 in the rear of the body is fixed to the front of a stock 73, securing the stock in place. A cocking knob 74 is slidably mounted in a curved slot 75 in the plate 71 and is able to engage, and rotate, the barrel bolt track assembly 34 to bring a barrel 17 up to the firing position when a magazine 50 has been changed. A carrying handle 76 having a low-light sight, is mounted on the torque tube 13 by front and rear legs 77. A front sight, adjustable for deviation by a knob 78 is mounted between the front legs and a rear sight 79, adjustable for elevation in slots and locked by a locking nut 80, is provided between the rear legs. A telescopic sight mounting plate 81 has a ring 82 removably engaged on the carrying handle 76 and posit¬ ioned by a locating wedge 83 and lock pin 84 urged into engagement by a spring 85. The operation of the gun will now be described. With the safety catch 68 applied, the magazine 50 is fitted to the gun, a cartridge being urged by the magazine spring against the magazine's induction hooks 49. The trigger 56 is depressed to cause the yoke 57 to swing down so that the bolt assembly 37 at bottom dead centre or "pick-up position" (see FIG. 5) is released The cocking knob 74 is moved in the direction of the arrow in FIG. 1 to rotate the barrel assembly in anticlockwise direction as indicated by an arrow in FIGS. 3 and 4. As the assembly of barrels 17, carrier 18 and bolt track assembly 34 is rotated, the abutment face 47 adjacent the bolt 37 engages the cartridges and pushes it from the indiction lugs 49 into the bolt slide track 36. As the assembly 34 continues to rotate,the bolt can track urges the bolt cam follower 40, and therefore the bolt, forward, At, or just before top dead centre, when the barrel 17 has moved to the firing position, the bolt assembly has fully inserted the cartridge into the barrel 17 ready to be fired. Before top dead centre is reached, the trigger 56 is released so that the bolt stops 59, 60 will engage the opposite or lowermost bolt to prevent further rotation of the barrel assembly. As the shaft 64 cannot rotate, the lost motion between the levers 61 , 62 is absorbed by the lost motion spring 63. The primary cam 67 blocks the firing cam track 45 as the barrel assembly is rotated and so the firing pin cam follower 44 is forced to follow the safety track, where the firing pin is held retarded relative to the bolt 37, until at top dead centre it is held against the rear o the secondary cam 70 by the spring 43. When the trigger is depressed, the yoke 57 and bolt stops 59, 60 again release the lower bolt which is ready to receive a cartridge from the magazine 50, the preceding bolt 37 at the 90° position already having received its cartridge. Simultaneously, the primary cam 67 is swung by the shaft 64 to open the firing cam track 45 to the oncoming firing pin cam follower 44. The firing pin cam follower 44 at top dead centre is released by the secondary cam 70 which is swung away by the shaft 64. The firing pin, driven forward by the spring 43, fires the cartridge. As the bullet travels along and from the barrel 17, the expandinggars can only escape from the barre mouth out from the gas outlet port 26. The gas escaping through the outlet port 26 forms an expanding pulse which, by expanding the volume of the top chamber 25, causes the rotor 22 and assembly of barrels 17 to rotate, the force of the pulse being determined by the position of the gas control valve 29. When exhaust port 28 is nearly closed by the valve, the firing rate is much higher than when the exhaust port 28 is fully open, so that the firing rate may be easily adjusted. With continued rotation of the assembly of barrels, the spent cartridge case is engaged by the extraction lugs 53 and discharged from the extraction port 52. At this position, the next succeeding bolt 34 has been moved to the firing position by the bolt cam track 41. The primary cam 67 has left the firing cam track 45 clear and so the firing pin cam follower 44 follows this track, which advances faster than the bolt cam track 41 , and so the firing pin is advanced relative to the bolt to fire a cartridge. The firing pin cam follower 44 may engage the rachet pawl on the secondary cam 70 so the firing pin is driven forward to fire the cartridge by both the cam pawl and the spring 43. The gun will continue to fire until the trigger is released and the bolt stops 59, 60 can engage the lowermost bolt 34 to prevent continued rotation of the barrel assembly. To ensure clear extraction of the spent cartridge cases through the extraction port 52, both the bolt and firing cam tracks 41 , 45 are such as to retract the bolts and firing pins at a faster rate ' after moving from the top dead centre firing position than they are advanced in moving to the firing position. To unload the gun, the magazine 50 is removed and the safety catch 68 is applied. The trigger 56 is depressed so that the bolt stops 59, 60 release the lower¬ most bolt. The primary cam ensures that the firing pin cam followers 44 can only follow the safety track. The barrel assembly is rotated by the cocking knob 74 until all the live cartridges in the gun have been discharged out the extraction port 52. The gun shown has four barrels but two or another even number of barrels may be provided. Alternate barrels may have right-handed and left- handed rifling to reduce any "run-off" of the gun as the assembly of barrels rotates. The invention may be applied not only to light machine guns but also may be applicable to heavy machine guns, for example from 0.50 inch calibre mounted on tripods to large calibre guns such as 20mm - 100mm anti-aircraft guns. In time, the rear face or the bolt cams followers 40 may wear, and to ensure that the bolts fully urge the cartridges into the barrels, removable head space adjusters 86, with wedges of differing thicknesses, may be fitted removably to the body 11, the wedges, when required, being engaged by the bolt cam followers 40 in the bolt cam track adjacent the firing position to ensure the bolts are urged fully forward. The embodiment described provides a light, yet rugged and reliable gun with a maximum rate of fire not previously achieved in light infantry machine or sub-machine guns or other automatic firearms hitherto used.

Claims: CLAIMS 1. A multi-barrel machine gun including: a gun body, as assembly of parallel gun barrels mounted on the body equidistantly from a longitudinal axis of rotation, drive means to rotate the barrels to bring them in sequence to a firing position, bolt means in the body to feed a cartridge to each barrel brought to firing position, and firing means to fire the cartridges the drive means being powered by expanding gas from the spent cartidges. 2. A multi-barrel machine gun according to Claim 1 wherein the drive means includes: a rotor fixed about the barrels within a stator on the body and eccentric to the axis of rotation of the barrels, the cavity between rotor and stator being divided into a plurality of chambers by vanes, and gas ports connecting the barrels to the chambers, high pressure gas from fired cartridges acting on the vanes rotating the rotor and barrels. 3. A multi-barrel machine gun according to Claim 2 wherein the drive means includes: an exhaust port for gas leads from the stator, and a control valve controls the effective size of the exhaust port, the speed of rotation of the barrels and the firing rate of the gun. 4. A multi-barrel machine gun according to any one of the preceding claims wherein the bolt means include: a bolt slide assembly in the body, connected to and rotatable with the barrels, a bolt aligned with each of the barrels and slidable in the bolt slide assembly, a firing pin slidable in each bolt and urged forwards by spring-loading means, a cam follower on each bolt, a cam follower on each firing pin, a bolt cam track and a firing pin cam track within the body and engaged, respectively, by the bolt cam follower and the firing pin cam follower, rotation of the bolt slide assembly causing each bolt moving towards firing position to engage a cartridge and drive it into a barrel, and to cause a firing pin to advance relative to the said bolt to fire the cartridge in the firing position. 5. A multi-barrel machine gun according to Claim 4 wherein: a safety track leads from the firing pin cam track, and safety catch means are provided for closing the firing pin cam track so that the firing pin cam follower cannot follow it but is directed into the safety track and so prevented the advance to firing position of the firing pin. 6. A multi-barrel machine gun according to either of Claims 4 or 5 wherein: a cartridge magazine is detachably mounted on the gun body, and has ' spring-loading means urging contained cartridges in sequence to a discharge outlet therefrom, the bolt slide assembly includes means for taking up a cartridge from the discharge outlet as each bolt in sequence is rotated to firing position, the gun body has an extraction port with extractio means for removing and ejecting spent cartridges from bolts leaving the firing position. 7. A multi-barrel gun substantially as herein described with reference to the accompanying drawings.

Inventors: KERFOOT RONALD ROSS, KERFOOT, RONALD, ROSS
Applicants: KERFOOT RONALD ROSS, KERFOOT, RONALD, ROSS
Application year: 1985
Main classification: F41D10
IPC codes: F41A5, F41A19, F41F1