Abstract: Pistol for slaughtering animals with captive projectile and hinged breech block, the breech block 13 being automatically locked to the breech 10 before the explosion by means of a balancing lever 37, inside the breech block, having a head 40 at one end for cocking the percussion pin 50 and a tooth 39 at the other end that fits onto a tooth 36 on the breech, the initial stroke made by the trigger 72 causing rotation of the lever 37 and hook-up onto the breech 10, continuance of the trigger's stroke causing said hook-up to be strengthened, releasing the percussion pin 50 for its forward movement.