Patent GB-500621-A (GB)
Title: Automatic firearms
IPC: F41A5/18
Filed: 1937-08-10
Abstract: 500,621. Automatic firearms. EIANE., H. O. Aug. 10, 1937, No. 22036. [Class 119] An automatic firearm having a breech-bolt controlled by a gas piston, has the operating handle of the breech-bolt moved into the line of sight when the magazine is empty, as a warning to the gunner. The firearm has a barrel 122, Fig. 2, and receiver 1 with a breech-bolt 2 and cartridge extractor 4 laterally mounted thereon. A port 138, Fig. 18, in the barrel communicates by a hand-controlled obturator 140 and automatic valve 137 with opposed cylinders 119, 127, in which slide pistons 109, 128, the latter of which is cushioned by a spring 135 whilst the piston 109 operates, through a hall-jointed rod 14, a cross-head 14a having a sleeve 108, Fig. 2. which slides on a guide 106 and is cushioned by a resilient washer 107. A sleeve 12 is secured to a rod 8 which is screwed into a lug 13 on the crosshead 14a, the sleeve being swung to engage over the breech bolt and then coupted to a. rod 9 parallel to the rod S, by mutilated threads 15, similar threads securing the rod 9 in the cross.head 14a. A thumb lever 17 fast on the rod 9 enables the rod to be turned either into locked engagement with the sleeve 12 and cross-head 14a cr to be released to allow the sleeve and breech-bolt to be dismantled. The breech. bolt 2, Fig. 13, is hollow and has a pair of diametrically opposite lugs 39 at the forward end and a lug 41 near the bolt handle. One of the lugs at the forward end is slit, radially to permit the passage of an ejector 43. Spiral slots 44 are provided in the bolt to accommodate a pin 22, Figs. I and21,which is mounted in the sleeve 12 and passes through a slot 50 in a firing pin 55 mounted within the breech. The slot 50 is of keyhole form and the pin 22 has a flattened part 22a so that the pin 22 may, when turned by the thumb lever 28, pass into a firing position allowing free movement of the firing pin, or may lock the firing pin either in the cocked or forward positions of the latter. The firing pin comprises a striking portion 54, Fig. 12, screwed on to a body 51 and locked thereon by interengagement with lugs on a sleeve 53 sliding on a hexagonal part 52 of the body 51. A bent 48 on a sleeve 60 on the firing pin coacts with a sear 85, Fig. 4, carrying a spring-urged lever 91 engaging the trigger piece 97, Fig. 2. A push-rod 94 coupled to the lever 91 makes contact with an eccentric groove in the breech-bolt, so that when the breech-bolt is unlocked, the lever 91 is disengaged from the trigger. The safety pin 22 has a semicircular part 21 which coacts with a member on the thumb lever 17 to prevent movement thereof to dismantle the gun, unless the gun is at safety. The breech-bolt is operated manually by the bolt lever 3 engaging cam faces on the receiver, in. order to fire the first shot, subsequent opening and closing of the breech-bolt being effected automatically by the action of the gas-driven cross-head pin in the cam slot 44. A thumb guard 165 protects the hand of the operator from the sweep of the breech-bolt. A hand-operated catch 77 is fitted, to engage over the forward end of the breech-bolt, to retain the breechbolt in open position to enable the magazine to be re-loaded. The magazine has a groove 162 which receives an extension of the magazine follower, this extension moving into the path of the breech-bolt, when the magazine isempty, to arrest the breech-bolt in such a position that the breech-bolt handle obscures the line, of sight.