• automatic pistol firing

    TITLE: automatic pistol fire as long as the trigger is depressed. Unlike automatic rifles and shotguns, automatic pistols are virtually never operated by combustion gases. In relatively low-powered pistols, the blowback mode of operation may be employed. In this system, the breechblock or bolt does not remain locked in firing position until the bullet has left the barrel but is free to be thrust backward by...
  • machine gun firing

    TITLE: machine gun
    ...the burning propellant in a cartridge to feed, load, lock, and fire each round and to extract and eject the empty cartridge case. This automatic operation may be accomplished by any of three ways: blowback, recoil, and gas operation.
    TITLE: small arm: Blowback
    SECTION: Blowback
    A third principle of machine-gun operation was often called blowback. In this, the action and barrel were never locked rigidly together; the barrel did not move, nor was there a gas cylinder and piston. To prevent the breech from opening so early that propellant gases would rupture the spent cartridge case, the block was heavy and the main spring strong. Also, there was usually a linkage of...
  • submachine gun firing

    TITLE: submachine gun
    Typically, expansion gases move a submachine gun bullet forward when the weapon is fired. The gases also push the heavy bolt back against a spring. The movement extracts and ejects the spent cartridge while the magazine spring pushes the next bullet into place. Holding the trigger down causes the strong spring behind the bolt to maintain its pressure until all the rounds have been used. New...