Abstract: A modular two-piece bolt system for firearms with blowback actions provides a rear bolt piece which detachably couples to plural different front bolt pieces each of different mass. The front bolt pieces have a similar configuration and common coupling interface which forms an interlocked relationship with a complementary configured coupling interface on the rear bolt piece to prevent axial separation of the pieces when the action of the firearm is cycled. The system allows various front bolt pieces to be selected and used interchangeably with the rear bolt piece so that a front bolt piece of proper mass can be matched to the energy of ammunition to be fired. The front and rear bolt pieces when coupled define a continuous extended longitudinal passage which receives the rear breech end portion of the firearm barrel therethrough to reduce the projected length of the barrel.

Abstract: A folding stock coupling system for a firearm. An openable/closeable hinge mechanism comprising front and rear hinge elements pivotably mounts the rear stock to the main body of the firearm. The hinge mechanism is selectively movable between a locked condition when the stock is unfolded and inline with the main body for firing, and an unlocked condition when the stock is folded forward and offset from the main body for compact carrying or storage. A manually movable actuating button of the hinge mechanism selectively locks or unlocks the rear to the front hinge members in the locked and unlocked conditions, respectively. Embodiments include a detent mechanism for removably retaining the folded position. An elongated rear mounting extension coupled to the rear hinge member provides a common stock mounting interface compatible for interchanging a plurality of different stocks to the firearm each sharing a common mounting profile.

Abstract: A folding stock coupling system for a firearm. An openable/closeable hinge mechanism comprising front and rear hinge elements pivotably mounts the rear stock to the main body of the firearm. The hinge mechanism is selectively movable between a locked condition when the stock is unfolded and inline with the main body for firing, and an unlocked condition when the stock is folded forward and offset from the main body for compact carrying or storage. A manually movable actuating button of the hinge mechanism selectively locks or unlocks the rear to the front hinge members in the locked and unlocked conditions, respectively. Embodiments include a detent mechanism for removably retaining the folded position. An elongated rear mounting extension coupled to the rear hinge member provides a common stock mounting interface compatible for interchanging a plurality of different stocks to the firearm each sharing a common mounting profile.

Abstract: A firearm with barrel extension comprises a receiver, a barrel supported by the receiver that defines an ammunition shell chamber, and a rotatable locking bolt having radial bolt lugs. The bolt is carried by a slide disposed in the receiver for forward and rearward movement. A barrel extension is mounted on a rear end of the barrel which includes radial bolt locking lugs that rotatably engage the bolt lugs when the bolt is in a closed locked breech position in battery with the head of a chambered shell. The barrel extension includes a rear facing annular rim seating surface formed integrally on the barrel extension as a unitary structural part thereof. The rim seating surface extends radially inwards from an interior surface of the barrel extension to engage and support the rear rim of the chambered shell. The headspacing is defined entirely by the barrel extension independently of the barrel.

Abstract: A firearm with barrel extension comprises a receiver, a barrel supported by the receiver that defines an ammunition shell chamber, and a rotatable locking bolt having radial bolt lugs. The bolt is carried by a slide disposed in the receiver for forward and rearward movement. A barrel extension is mounted on a rear end of the barrel which includes radial bolt locking lugs that rotatably engage the bolt lugs when the bolt is in a closed locked breech position in battery with the head of a chambered shell. The barrel extension includes a rear facing annular rim seating surface formed integrally on the barrel extension as a unitary structural part thereof. The rim seating surface extends radially inwards from an interior surface of the barrel extension to engage and support the rear rim of the chambered shell. The headspacing is defined entirely by the barrel extension independently of the barrel.