(under subclass 1.7) A gun comprising an expansible chamber associated with the barrel means and having at least one movable wall formed by a freely movable reaction mass means which may be accelerated by those forces in the pressurized gas which are developed counter to those forces therein which propel the projectile.
(1) Note. The expansible chamber may be a second barrel means arranged to cooperate with the gun-barrel means, and the reaction mass may be in the form of a second projectile means adapted to be projected from the gun by the forces in the pressurized gas which act counter to those which act to propel the first projectile.
