Patent GB-579110-A (GB)
Title: Improvements in machine guns
IPC: F41A35/06
Filed: 1935-08-16
Abstract: 579,110. Machine guhs. ADAMS, E. S. R., and WILLMOTT, W. Aug. 16, 1935, No. 23058. [Class 92 (ii)] In a gas-operated machine gun the reciprocating 'breechbolt 20 is locked in firing position by side levers or dogs 19 having a vertical pivoting movement on the breech-bolt and maintained against inclined shoulders 29 on the gunbody 2 by cams 18 on the gas piston-rod 15. The arrangement is such that the reaction of the shoulders tends to unlock the breech-bolt, the dogs being caused to start the vertical locking movement by fixed projections 30 on the body and to start the vertical unlocking movement by the inclined shoulders 29. The piston rod carries a radial post 15B, Fig. 9, for the firing- striker 17, the post limiting the forward movement of the piston-rod by contact with 'the breech-bolt which engages the rear face of the gun barrel 1. The barrel is adjustable axially for head space by a notched screwed sleeve 3, Fig. 7, retained by a transverse cotter 5, Fig. 6, and collar 6, as described in Specification 579,112. The piston-rod is held in cocked position by a trigger-operated pivoted sear 52 mounted on a spring-controlled slide 53 and engages a fixed ramp 57 that moves the sear into full engagement with the bent 23 on the piston-rod as described in Specification 579,111. The gun shown also includes cartridge case extracting and ejecting mechanism as described in Specification 579,113. On firing, the gas-piston 15, Fig. 7, operated by the tapped gun gases moves rearwards to uncover the gasrelease ports x near the gas-deflector 14. The piston-rod moves rearwards against the action of a return spring 25 and removes the cams 18 from beneath the dogs 19 to permit of their release by the inclined shoulders 29, the breech-bolt and piston-rod then moving rearwards together until a spring buffer 46 is engaged by the bolt. The recoiling parts are then retained in the " breech open " position by the sear 52 engaging the bent 23 on the pistonrod and, if necessary, by a slidable safety catch 24. On release of the sear by trigger 58, the breech bolt moves forward and a pivoted member 33 on the top of the bolt engages the base. of a cartridge in the drum magazine and loads the cartridge into the gun chamber, the bullet being guided by a member 35. Just before the breech bolt engages the barrel, the dogs 19 are started upwardly by the fixed stop 30 and then moved into full engagement with the shoulders 29 by the cams 18. The breech may be opened by hand by a sliding cocking- handle 22 engaging a projection on the pistonrod. Extraction of the case is effected by a rocking spring-controlled extractor 31 and ejection by a pivoted member 42 engaged by a cam on the breech bolt. The parts are adaptable for extraction and ejection on either side of the gun. The drum-magazine is retained by a readily releasable rear catch 37 which forces the magazine forwardly into engagement with a front spring catch 39, Fig. 7. The foresight is detachably mounted on a socket 8 attached to the muzzle by the screwed flash-obscurer 7 and nut 9, and the rear sight is detachably mounted in a rear socket 38. An adjustable pivoted pad 50 for the sighter's chin is provided.