GB879948A - Improvements in and relating to breech mechanisms for automatic firearms - Google Patents

Abstract

879,948. Automatic firearms. VERWALTUNGSGESELLSCHAFT DER WERKZEUGMASCHINENFABRIK OERLIKON. Feb. 3, 1958 [Feb. 7, 1957], No. 3451/58. Class 92. A breech mechanism for an automatic firearm has a casing 10 with an inclined abutment face 10a in which is a movable, two-part breech block comprising a head 2 which takes the cartridge thrust and a rear part 4 which engages the head 2 abuts a recoil spring 6 and has an inclined abutment face 4a from which a tongue 9 extends towards the head 2. The head 2 moves due to reaction from a fired cartridge 11 successively from an inertia-locked position (Fig. 2), to an intermediate, positively-locked positive (Fig. 3) and thence to a recoiled position (Fig. 4). As the head 2 recoils the prismatic rearfaces of locking flaps 8 first engage both the abutment faces 10a and 4a thereby accelerating the rear part 4 relative to the head 2; further inward movement of the flaps 8 is then prevented by contact with the flat walls 4b of the tongue 9, so that the rearward flap-faces continue to abut the faces 10a and positively lock the breech head 2 until the part 4 moves further back to withdraw the tongue 9 from between the flaps (Fig. 3). The flaps then complete their inward movement and permit the head 2 to continue its recoil, pulled back by a lug 4c on the part 4. A firing pin 5 is pivoted on a pin 14 so that its tip falls out of alignment with the firing-hole in the head 2 when the parts 2 and 4 are separated. The head carries an extractor 3 which engages the rim of the cartridge. Prismatic locking blocks, sliding longitudinally and transversely (Fig. 5, not shown), may take the place of the hinged locking prisms 8.