GB1247164A - Open chamber breech mechanism with scarfed firing strap - Google Patents

Abstract

1,247,164. Open chamber firearm. TRW Inc. 7 Oct., 1968 [6 Oct., 1967], No. 47509/68. Heading F3C. An open chamber breech mechanism for a firearm comprises a breech frame in which a cylinder 26 having at least one open chamber 40 is rotatably mounted. The cylinder 26 is rotated through an infeed position in which cased cartridges 56 are fed laterally into the chamber to a firing position and then to a cartridge ejector position. The cylinder 26 and frame define therebetween gas leakage interfaces about the open side of the firing chamber which interfaces are sealed by expansion of a fired cartridge case under the action of the propellent gases produced thereby. The curvature of the cylinder 26 and adjacent wall of the breech frame are of substantially the same curvature but the wall of the breech frame recedes from the cylinder at a small angle e.g. 0À025 radians in the direction of the cylinder rotation adjacent the firing position to relieve frictional forces acting between the expended cartridge case and the breech frame wall. With this scarfing the propellent gases through the cartridge case also produce a rotational force in the direction of rotation of the cylinder. Although the breech mechanism may be applied to fixed barrel weapons, propellent gas powered tools, such as slaughter guns, cable splicers, stud drivers and oil well perforators the particularly described embodiment comprises a four chamber cylinderfour barrel rotatable assembly firearm (Fig. 1, not shown).