A firearm including a basic action system having differential recoil, blow-back operation with moving barrel and a firing mechanism for use in conjunction with the basic action system of the invention or any other type of system operable to fire from a closed-bolt position and an open-bolt position. The basic action system utilizes a single spring which positively positions the bolt and barrel for semi-automatic, closed-bolt firing, while also providing the necessary spring and positioning action for open-bolt, differential recoil, blow-back operation. The firing mechanism of the invention provides for semi-automatic fire from the closed-bolt position, and for full automatic fire from the open bolt position, with a selector to permit selection by the gunner.
A relatively simple repeating firearm is disclosed which includes a sliding bolt which is removably housed within a firearm housing and which is biased into a bullet loading and firing position by means of springs provided in an overlapping fashion with a longitudinal extent of the bolt to thereby reduce the overall length of the firearm. A short stroke for the sliding bolt is provided to enable a rapid firing of the firearm. The sliding bolt and firing mechanism contained thereon are easily removed from the housing by a removable rear cover with the firearm accommodating different calibers of bullets by replacement of the sliding bolt as well as a removable barrel which contains the firing chamber therein.
