A gun device allowing replacement of barrels with different sizes, having a gun body, one end of the gun body has an opening. The opening outer edge has a threading and a positioning slot. The gun body connects with a first size barrel by connecting the threading with a lock. The gun device further comprising: a guide adapter, a second size barrel and a barrel key. The guide adapter has a positioning body, a projecting part, and a first groove, the projecting part alignment connects with the positioning slot. The second size barrel has a second groove, the first groove corresponding with the second groove.

A secondary firearm with a rail mount attachable to a rail assembly of a primary firearm is disclosed. The secondary firearm comprises a body having at least one retaining pin hole and a bolt stop hole and a housing disposed about the body. The housing comprises at least one retaining pin aperture and/or a bolt stop aperture. The secondary firearm also includes at least one fastener disposed within at least one of the at least one retaining pin aperture and the at least one retaining pin hole and/or the bolt stop aperture and the bolt stop hole to fasten the housing to the body.

A firearm with a clamping device for attaching a barrel with a barrel extension, where the barrel extension on the one hand, and a seat on the other hand, possibly directly the upper receiver, are connected to one another by means of a clamp and the fixing of the barrel extension on the upper receiver by means of a tension lever that is rotatable about a common axis of rotation running normal to the weapon center plane between two end positions, the ready-to-fire position and the dismantling position, with at least one clamping section and a grip and a cam formed on the tension lever.

A system for securing a barrel to a receiver of a rifle includes a barrel extension and a locking wedge. The barrel extension receives threads on the barrel and has a protuberance. The locking wedge is secured in an aperture in the receiver by a fastener. The locking wedge has a side parallel to the aperture, and a cam side disposed at an angle. The locking wedge is movable in a direction perpendicular to the barrel axis. The cam side is disposed against the protuberance. Tightening the fastener causes the cam side of the locking wedge to urge the protuberance of the barrel extension along the barrel axis in a direction away from the muzzle end of the barrel into the receiver.

A system for securing a barrel to a receiver of a rifle includes a barrel extension and a locking wedge. The barrel extension receives threads on the barrel and has a protuberance. The locking wedge is secured in an aperture in the receiver by a fastener. The locking wedge has a side parallel to the aperture, and a cam side disposed at an angle. The locking wedge is movable in a direction perpendicular to the barrel axis. The cam side is disposed against the protuberance. Tightening the fastener causes the cam side of the locking wedge to urge the protuberance of the barrel extension along the barrel axis in a direction away from the muzzle end of the barrel into the receiver.

A barrel nut assembly for a firearm is disclosed. The barrel nut assembly may include a barrel nut comprising a plurality of expansion flanges. The barrel nut assembly also may include an expansion plug comprising an expansion surface. The expansion surface may be configured to abut and expand the plurality of expansion flanges when the expansion plug is attached to the barrel nut.

A slide assembly quick release pin and arm that secure a recoil assembly within a slide. The pin is inserted through a pair of apertures in a front portion of the slide and through a bore in the nose portion of the recoil assembly aligned between the apertures. As the pin secures the recoil assembly within the slide an arm attached to the end of the pin rests in a recess, flush to the body of the slide in a locked orientation. The pin arm is rotated from a locked orientation within the recess in the assembled configuration to an unlocked orientation out of the recess before the firearm is disassembled. Additionally, the arm acts as a handle for grasping and rotating to provide a mechanical advantage when a user is removing or inserting the pin into the apertures and bore.

A take-down rifle including modular components. A first and a second rifle section comprising first and second receiver portions, respectively, allow the rifle to be quickly assembled and disassembled. The first rifle section also includes a rifle barrel. Mounting points on the first rifle section allow a coupled optical sight to remain fixed in relation to the barrel after assembly or disassembly so that the optical sight remains zeroed.

Quick take-down firearms and methods of using quick-take down firearms. The quick-take down includes an upper receiver coupling and a barrel coupling. The quick take-down can be unlocked by sliding a sliding lock collar in a translational motion to an unlocked position to release locking elements from a locked configuration. In the unlocked position, a barrel and handguard may be installed onto and removed from the upper receiver of the firearm. Releasing the sliding lock collar returns it to a locked position, securing the barrel and handguard to the upper receiver.

A modular firearm system capable of easily attaching and detaching an upper receiver and a barrel is disclosed. The upper receiver is operably coupled to a bearing case. A biasing member is positioned on the bearing case. A plurality of bearings are positioned on the bearing case. A spring sleeve is engageable with the biasing member and circumscribes the bearing case, biasing member and bearings. A face plate is positioned adjacent to the bearing case and fixedly coupled thereto. The face plate engages the spring sleeve such that the biasing member and bearings are enclosed within the spring sleeve and the face plate. A barrel sleeve is operably coupled to the barrel. In an engaged state, the barrel sleeve is positioned within the bearing case and the bearings are positioned between the barrel sleeve and bearing case such that the upper receiver and barrel are substantially aligned.