GB306854A - Improvements in machine guns and other automatic firearms - Google Patents

Abstract

306,854. Revelli, B. A. Aug. 25, 1927. Machine guns.-Relates to machine guns and like automatic guns of the kind in which the breech-block is not positively locked at the moment of firing, and consists in the combination of means for effecting the percussion a little before the closure of the breech, with means for admitting the pressure of the exploded charge to a spaces around the neck of the cartridge to balance the internal pressure thereon. As shown in Fig. 6, small longitudinal grooves 45 are formed in the chamber of the gun barrel around the neck of the cartridge and extending slightly beyond the front end of the cartridge. The gas pressure thus acts both inside and outside the neck of the cartridge, and as a result there is no risk of deformation of the cartridge or of escape of gas. The barrel 1 is attached to the front plug 3, Fig. 1, of the breech casing 2, by a bayonet-like joint locked by a spring catch. The breech-block 6 is cylindrical in form and slidably mounted in the breech casing 2, which may be made from a Mannesman tube. A handle 9 is attached to the breech-block 6 by a pin 10, which is passed through a hole in the breech casing; and the handle 9 is guided in a rectilinear slot 13 in the breech casing. The breech-block contains a spring- cushioned sliding firing-pin 12, and a hammer 15 pivoted at 16 and adapted to strike and be deflected by a fixed stop 17 forming part of an ejector to fire the cartridge a little before the breech is closed. An extractor 19 is pivoted in a longitudinal groove 60 in the breech-block, and is wedged out by a fixed incline 21 when the breech is closed. After the initial short part of the recoil movement of the breech-block, the extractor 19 swings in and seizes the spent cartridge and withdraws it from the gun chamber. The surface of the breech-block 6 is made with longitudinal grooves 42, Fig. 2a, so that dust entering thereinto may not oppose any resistance to the sliding of the breech-block. This block is held cocked by a sear 35 operated by a trigger 33 controlled by a spring 34, and this trigger mechanism is contained in a casing 32 in front of a handle 41. The recoil of the breech-block 6 is taken up by a spring 7, Fig. 1<a>, and a buffer 40; and a screw plug may be provided at the rear end of the spring 7 to adjust the compression of that spring. A butt 36 is provided, but may be detached and replaced by a plug with a handle. In a modification of the firing-mechanism, the hammer 15 is not pivoted to the breech-block but takes a pivotal bearing against the front of the handle 9. In another modification, Fig. 5, the hammer 48 has a projection 48<1> which acts as the firing pin and fires the cartridge when the hammer is deflected about its pivot 49 on the breech-block 6 by the impact of a lug 48<11> of the hammer against the face of the plug 3 of the breech casing.