Patent GB-963120-A (GB)
Title: Improvements in breech mechanisms for automatic firearms having a recoiling barrel
IPC: F41A9/32
Filed: 1962-05-24
Abstract: 963,120. Automatic firearms. BREVETS AERO-MECHANIQUES S.A. May 24, 1962 [June 2, 1961; June 21, 1961], No. 20044/62. Heading F3C. Relates to a breech mechanism for an automatic firearm having a barrel 4, Fig. 1a, fixed to a breech case 6, 8, the barrel and breech case recoiling relative to an external casing 1 against the action of a spring 10. A breech block 18 is slidable in the breech case, a firing pin 19 is slidable in the breech block and locking members 24 pivotally mounted in the breech block are engaged by the firing pin 19 during its forward movement in the breech block and moved outwardly to engage the breech case and lock the breech block thereto during firing. The breech case is provided with two rearwardly projecting arms 9, Figs. 1a, 4a, each arm 9 having a lever 13 pivoted at 13a and provided with lower and upper end projections 14, 16. Projection 14 is adapted to come, after about 20% of the recoil stroke of the barrel 4, into contact with an abutment 15 on a breech block guide 36 fixed to the external casing 1, to cause the lever 13 to pivot and the projection 16 to push rearwardly a finger 17 carried by the firing pin 19. The firing pin is thus pushed to the rear relatively to the breech block and a surface 24a, Fig. 13, on each locking member 24 is disengaged from the firing pin to permit the inward movement and release of the locking members. However, the inclinations of the co-operating surfaces 31, 32 of the locking members and breech case are such that this release of the locking members does not take place until the whole of the elements 4, 6, 18 has moved towards the rear in the casing 1 by an amount corresponding to about 40% of the recoil stroke of the breech block 18 when oblique surfaces 35 on the breech block guide 36 engage corresponding surfaces 34 on the locking members to move them inwardly and unlock the breech block from the breech case and permit recoil thereof relative to the barrel and breech case. The rear end of the breech block 18 is provided with catches 37, Figs. 1a 1b, for engagement with sears 90, and at the forward end of the breech block a pivoted extractor 38, Fig. 2a, is provided. An ejector rod 39 is guided in the breech block and is adapted to move forwardly relative to the breech block when its rear end engages a sleeve 21 for the firing pin spring 20, the cartridges being ejected through a passage 3 provided in the casing 1. A transverse spindle 40 at the rear end of the breech block carries a roller 41 serving to operate the belt feed mechanism and a transverse piece 43, Fig. 1a, links the breech block and firing pin with axial play, the ends of the piece 43 being fixed in a U-shaped part 44, Figs. 1a, 4b, extending under the breech block 18. This part 44 carries the fingers 17 and the middle portion of part 44 forms a projection 45, Figs. 2a, 4b, adapted to co-operate with gun cocking means. In order to cock the gun when the breech is closed, there is provided an endless chain 52, Figs. 2a, 2b, extending between two pinions 53, 54, the rear pinion 54 being actuated by means of a pawl and ratchet lever 56, Fig. 4b. A finger 57, Fig. 2a, on the chain 52 is adapted to engage the projection 45 of the part 44 and move the breech block back until held by the sears. This is combined with mechanism for retracting the locking members 24, Fig. 32 (not shown). The gun is provided with a belt feed mechanism in a frame 58, Fig. 2a, fixed on the casing 1 above an upper opening in the casing and comprising a central head 59 reciprocated transversely by a lever arm 64 mounted on a cam rod 60 having a helical groove 63 which is engaged by the roller 41 on the breech block 18. The head 59 is fixed to the rear of a pawl carriage 67 guided in the frame 58 by means of rollers 68, the carriage 67 having two feed pawls 71, 72 for feeding the cartridges. In addition the frame 58 carries a pair of holding pawls 74, 75 and a pair of abutment pawls 76, 77, Figs. 18- 21. The pawls 74-77 are adapted to prevent the cartridge following the cartridge to be fired from moving either frontwardly or rearwardly from its position 73a, but the abutment pawls 76, 77 are adapted to be lifted subsequently by cam devices 81, 82 to permit subsequent feed of the cartridge in position 73a by the feed pawls 71, 72. The frame 58 also carries a deflector pawl 85, Fig. 22 (not shown), for pushing the cartridge down into a position for feed into the cartridge chamber. Mechanism is provided for moving sears 90 Fig. 1b away from each other in order to start firing and for bringing the sears towards each other to engage the catches 37 in order to stop firing and this is effected by an actuating arm 108 controlling the movement of wedges 97 acting on the sears 90. In addition mechanism is also provided so that firing is automatically stopped after the last cartridge has been fired and the breech block remains held in its rearmost position, so that a fresh cartridge belt may be introduced without having to cock the gun before firing. In a modification, Fig. 12 (not shown) gases vented from the barrel are used additionally to push back the recoiling parts with respect to the casing 1. Specification 963,119 is referred to.