Firearm

A firearm, particularly a gun operating by recoil exploitation, comprising:

• a frame;
• a barrel which has a longitudinal axis arranged in a median plane of the gun which starts in the front-back direction of the gun and divides said gun into a right part and a left part;
• a hand grip;
• a breechblock slidable along the frame parallel to the longitudinal axis of the barrel for the closing of a breech of the barrel;
• a striker slidable in the breechblock parallel to the longitudinal axis of the barrel;
• a longitudinal elastic device for recovery of recoil kinetic energy of the breechblock for rearming the striker;
• a release lever having a coupling position and a release position of the striker;
• a single action trigger mechanism comprising a trigger and a trigger transmission rod operatively connected to the trigger and to the release lever, further comprising an antagonist lever to said release lever, the mass of said antagonist lever being distributed and arranged to strain said antagonist lever with inertial forces that contrast said release lever to prevent the accidental release of the striker.