Abstract: A striking mechanism (20) for the semi-automatic operation of a cartridge firing firearm (10) providing, in combination, a receiver (12); a barrel (11) attached to the receiver; a gas operated slide assembly (13) providing a slide (14) movable within the receiver; a magazine (19), supplying a plurality of cartridges (29), carried by the receiver; and a trigger assembly (26) attached to the receiver and providing a hammer (28); the striking mechanism comprising a bolt (21) reciprocable within the receiver and engageable with the breach (32) of the barrel and the face of a cartridge chambered therein, the bolt carrying a primary firing pin (22); a bolt lock (23) pivotally linked to the bolt for selectively locking the bolt within the receiver; a secondary firing pin assembly (24) pivotally linked to the bolt lock and to the slide, the secondary firing pin assembly providing a secondary firing pin (25), engageable with the hammer and the primary firing pin thereby to strike the primer of a cartridge chambered wi