Patent GB-129253-A (GB)
Title: Improvement in Machine Guns.
Inventor: FORBES WILLIAM DUNDERDALE
IPC: F41A3/26
Filed: 1918-12-18
Abstract: 129,253. Forbes, W. D., and McKenzie, T. W. July 5, 1918, [Convention date]. Machine guns.-Relates to long-recoil boltaction guns of the' kind in which the barrel, breech-bolt, and bolt operating-sleeve recoil together, the return of the barrel to firing position releasing the bolt, and the return of the bolt releasing the operating-sleeve. The invention consists in the combination of (1) a hollow operating- sleeve in which slides the breech-bolt and to which the firing pin is attached, (2) anchoring means movable with the breech-bolt and adapted to engage a fixed stop to hold the breech bolt against advance until the barrel has returned, and (3) means for holding the operating-sleeve cocked until the breech-bolt is in forward position ready to be locked. In the form shown in Fig. 1, the barrel 92, breech bolt 67, and operating-sleeve 53, recoil together against the action of springs 101, 56 in an outer tube 25 provided with a loading opening 29 with magazine 28, and an ejection opening 111. The breech bolt is rotated for unlocking, during recoil, by the engagement of a pin on the tube 25 with an inclined slot in the sleeve 53, and the breech bolt is engaged by a sear 32 whilst the barrel returns. The parts then occupy the position shown in Fig. 1. An automatic catch 112, Fig. 12, of strip form, engages by its flexible end 114 a fixed stop 99 to prevent the breech bolt returning until the barrel, on reaching its forward position, presses down the part 114. The sear 32 pivoted at 33 carries at its rear end a hinged trigger 46, an extension 42 of which engages the fixed casing. An extension 41 of the sear is engaged by a vertically pivoted safety lever 48 which must be moved aside before the trigger can be pulled. The sear is under the control of a spring 34 which also serves to control a pivoted magazine latch 35. When the trigger is pulled, the sear is rocked about its pivot 33, and the breech bolt moves forward under the action of a pair of springs 121<a>, 121<b>, its finger 87 pushing the cartridge from the magazine up inclines 39, 89 into the breech chamber. The operating sleeve 53 carrying the firing pin 70 is meanwhile held in rear position by a latch 58 engaging a recess 63 in the fixed casing, this latch, running in a groove in the breech bolt, being tripped when the breech bolt reaches its forward position. The operating-sleeve then moves forward under the action of its spring 56 to first rotate the breech bolt into, locking engagement with the barrel and then fire the cartridge. The firing pin is mounted within the operating sleeve with slight play against, the action of a spring 81 so as to exert pressure on the cartridge case during extraction, to turn the case about the extractor 85 and eject it through the opening 111. A hand-operating sleeve 92 has a pin 110 which bears against a collar 109 fixed to the barrel, so that the barrel may be moved rearwards to initially open the breech. The Specification as open to inspection under Sect. 91 (3) (a) also describes means whereby air is kept in motion over the barrel for cooling purposes by the action of pistons 102,104 on the barrel working in cylindrical casings 194, 195 provided with ports 105, 106, 107 through which the air is drawn and expelled as the barrel reciprocates. This subject-matter does not appear in the Specification as accepted.