Abstract: A breech assembly for an automatic weapon having a barrel extension aligned with and extending outwardly from the rifle bore. The barrel extension has a throughbore aligned with the rifle bore and a non-circular locking recess at a rear end of fee barrel extension. The barrel extension also includes an internal thread in the throughbore. An elongated bolt includes an external thread complementary to the infernal thread hi the barrel extension. The bolt is mounted to a bolt carrier that is longitudinally slidably mounted to the gun body. Longitudinal movement of the bolt carrier simultaneously longitudinally and rotatably drives the bolt so that the bolt thread is threaded into the barrel extension.

Abstract: A breech assembly for a gun having a barrel and a barrel extension extending rearwardly from the barrel. The barrel extension includes a throughbore aligned with the barrel as well as a radially inwardly extending annular abutment surface adjacent the rear end of the barrel extension. An elongated bolt is axially slidably received through the barrel extension throughbore when moved to a firing position. An expandable mandrel is mounted to the bolt so that the mandrel surrounds at least a portion of the bolt. An expansion pin is slidably mounted on the bolt and movable between a retracted position in which the mandrel collapses onto the bolt and allows removal of the bolt from the barrel extension, and an inserted position in which at least a portion of the expansion pin is inserted into the mandrel and deflects the mandrel radially outwardly so that a rear end of the mandrel abuts against the abutment surface and locks the bolt to the barrel extension.

Abstract: A breech assembly for an automatic weapon having a barrel extension aligned with and extending outwardly from the rifle bore. The barrel extension has a throughbore aligned with the rifle bore and a non-circular locking recess at a rear end of fee barrel extension. The barrel extension also includes an internal thread in the throughbore. An elongated bolt includes an external thread complementary to the infernal thread hi the barrel extension. The bolt is mounted to a bolt carrier that is longitudinally slidably mounted to the gun body. Longitudinal movement of the bolt carrier simultaneously longitudinally and rotatably drives the bolt so that the bolt thread is threaded into the barrel extension.

Abstract: A breech assembly for a gun having a barrel and a barrel extension extending rearwardly from the barrel. The barrel extension includes a throughbore aligned with the barrel as well as a radially inwardly extending annular abutment surface adjacent the rear end of the barrel extension. An elongated bolt is axially slidably received through the barrel extension throughbore when moved to a firing position. An expandable mandrel is mounted to the bolt so that the mandrel surrounds at least a portion of the bolt. An expansion pin is slidably mounted on the bolt and movable between a retracted position m winch the mandrel collapses onto the bolt and allows removal of the bolt from the barrel extension, and an inserted position in which at least a portion of the expansion pin is inserted into the mandrel and deflects the mandrel radially outwardly so that a rear end of the mandrel abuts against the abutment surface and locks the bolt to the barrel extension.