BLOWBACK

(*) 1. Escape, to the rear and under pressure, of gases formed during the firing of the weapon. Blowback may be caused by a defective breech mechanism, a ruptured cartridge case, or a faulty primer. 2. Type of weapon operation in which the force of expanding gases acting to the rear against the face of the bolt furnishes all the energy required to initiate the complete cycle of operation. A weapon which employs this method of operation is characterized by the absence of any breech-lock or bolt-lock mechanism.