Firearm barrel change apparatus for a firearm having a receiver and a barrel with a portion configured to slide into the receiver. The firearm barrel change apparatus also includes a barrel receiving nut having provisions for slidably receiving the inner portion of a firearm barrel and a barrel retention member. The barrel retention member has a portion thereof sized and shaped to cooperate with the barrel receiving nut to lock the firearm barrel to the receiver. A special handguard assembly is also provided that allows the barrel retention member to be used with the barrel receiving nut without removing the handguard assembly.

A repeating shot gun, in particular a automatic shot gun, is provided with at least one barrel (29) which is rigidly attached to a plastic housing (1) when the gun is assembled, the shot gun having a coupling (3) formed either from a metal or from a material having properties similar to those of metals with respect to deformation and strength and having a barrel receiver (5) which is rigidly positioned in the housing (1), such that the barrel receiver (5) substantially coaxially surrounds the rear portion of the barrel (29) and the barrel (29) is in close-fitting engagement with the barrel receiver (5).

A flex-plate adapter for a takedown firearm has front and rear sections. The rear section includes adjustment screws to change the gap between the front and rear sections. Guide pins are included for assuring proper alignment between the front and rear sections. The adjustable gap between the front and rear sections of the flex-plate adapter provides compensation for thread wear. A magazine cutoff provides a manual cutoff for retaining ammunition in the magazine whether the rifle is assembled or disassembled. A cutoff lock prevents the accidental movement of the magazine cutoff.

A rifle has a barrel which is mounted detachably in the housing in that pairs of clamping rings (11, 12) are provided between the rear part of the barrel (5) and the inner cylindrical surface (3) of the housing (1), which clamping rings (11, 12) have mutually facing conical surfaces and are pressed axially by a clamping nut (13) against a collar (7) on the barrel (5). Such a barrel mounting can also be used for a housing made of light alloy, with simple production and with production-dependent tolerances and alignment errors being eliminated.

The description refers to a rifle with a shell (2) to be inserted into a shaft (1), to which shell (2) a barrel (3) can be connected, and with a mounting rail (5) fixed to the barrel (3) for accommodating an aiming telescope (17) projecting backward beyond the barrel (3). To achieve favorable construction. features, it is suggested that the mounting rail (5) for accommodating the aiming telescope (17) engages into a shell guide (6).