Disclosed is a chamber closing piece (1) for firearms. Said chamber closing piece (1) can be rotatably and reversibly moved forward in the direction of the barrel muzzle (3) and rearward in the direction of the rear stock (4) and comprises one or several mechanisms (8) for indirectly or directly firing a bullet (9) that faces the muzzle in relation to the chamber closing piece (1). Said mechanism (8) for firing the ammunition is based on an electrical and/or thermal and/or optical and/or laser-based active principle.