GB191316801A - Improvements in Automatic Firearms. - Google Patents

Abstract

16,801. Krnka, K. Aug. 26, 1912, [Convention date]. Breech actions, sliding breech-block.-Relates to automatic guns in which, upon discharge, the bolt head is able to move back a short distance to impart energy to a momentum block which effects the unlocking, as described in Specification 13,946/09, and consists in arranging the space which allows this backward movement behind the impact shoulders of the front pair of locking-lugs on the bolt, instead of between the bolt and the bolt head. The locking-surfaces 14, 15, Figs. 1, 2, and 3, of the two pairs of locking-lugs on the bolt b are of different pitch, the pitch of the second surface 15 being too great to secure positive locking. When the gun is in the position for firing, as shown in Fig. 2, there is a small space z behind the locking-surface 14. After the discharge, the breechbolt moves back this distance z, at the same time being rotated through a small angle, 16 degrees in the example shown. This rotation drives back the non-rotary momentum block c, Fig. 4, which is connected to the bolt by lugs 2<I>, 2<II>, 2<III>, 2<IV> and inclined grooves as described in the above-mentioned Specification. In the example given, a backward movement of the breech-block of 0À8 mm. produces a positive initial movement of the momentum block of 3À5 mm. The unlocking-grooves in the breechbolt are wider than the lugs on the momentum block, as shown in Fig. 5, so that the momentum block has a slight lost motion before it begins to rotate the bolt. The action may be so arranged that a single spring ef, Fig. 6, serves both as the firing-spring and the closing-spring. In this case, the firing-pin d, block c, and bolt b are all driven forward by the spring until the firing-pin is caught by the sear, the locking being then completed by momentum.