A rifle comprises a quad lock multicaliber receiver, a barrel extension, a bolt, and a projection engageable with the receiver. The barrel extension includes a cartridge chamber and is securable in an end of the receiver. The bolt is slideable in the receiver and engages a cartridge in the cartridge chamber during the firing phase. The projection comprises locking bars extending through the receiver, and is moveable between locked and unlocked positions to allow for securing and removing of the barrel extension, respectively. Positioning bars are disposed on either side of the receiver split parallel to its longitudinal axis. The locking bars are disposed between these positioning bars and the barrel extension such that when the positioning bars are urged toward each other the receiver split is closed and the positioning bars urge the locking bars toward and into locking grooves to secure the barrel extension in the receiver.

A 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 plurality of bearings are positioned on the bearing case for engaging dimpled slots on the surface of the barrel. A spring sleeve is engageable with the biasing member and circumscribes the bearing case, biasing member and bearings. A dust cover is engageable with the spring sleeve. In an engaged state, the bearing case, the spring sleeve, and the dust cover are assembled such that the upper receiver and barrel are substantially aligned.

A rifle comprises a quad lock multicaliber receiver, a barrel extension, a bolt, and a projection engageable with the receiver. The barrel extension includes a cartridge chamber and is securable in an end of the receiver. The bolt is slideable in the receiver and engages a cartridge in the cartridge chamber during the firing phase. The projection comprises locking bars extending through the receiver, and is moveable between locked and unlocked positions to allow for securing and removing of the barrel extension, respectively. Positioning bars are disposed on either side of the receiver split parallel to its longitudinal axis. The locking bars are disposed between these positioning bars and the barrel extension such that when the positioning bars are urged toward each other the receiver split is closed and the positioning bars urge the locking bars toward and into locking grooves to secure the barrel extension in the receiver.

A rifle comprises a quad lock multicaliber receiver, a barrel extension, a bolt, and a projection engageable with the receiver. The barrel extension includes a cartridge chamber and is securable in an end of the receiver. The bolt is slideable in the receiver and engages a cartridge in the cartridge chamber during the firing phase. The projection comprises locking bars extending through the receiver, and is moveable between locked and unlocked positions to allow for securing and removing of the barrel extension, respectively. Positioning bars are disposed on either side of the receiver split parallel to its longitudinal axis. The locking bars are disposed between these positioning bars and the barrel extension such that when the positioning bars are urged toward each other the receiver split is closed and the positioning bars urge the locking bars toward and into locking grooves to secure the barrel extension in the receiver.

A handguard assembly for a firearm includes a handguard with an internal clamping area. A single-piece index block includes a securing portion for connecting to the handguard and an indexing extension for engaging an indexing feature on the upper receiver of the firearm. The handguard includes internal ribs that provide discrete clamping surfaces for engaging a barrel nut of the firearm. Connecting the index block to the handguard generates a continuous clamping action in the handguard which acts through the ribs to apply a radially-directed circumferentially-applied clamping force on a barrel nut through the discrete clamping surfaces. The indexing feature of the index block engages an indexing feature of the upper receiver to ensure proper alignment of the handguard and the upper receiver.

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 handguard assembly for a firearm includes a handguard with an internal clamping area. A single-piece index block includes a securing portion for connecting to the handguard and an indexing extension for engaging an indexing feature on the upper receiver of the firearm. The handguard includes internal ribs that provide discrete clamping surfaces for engaging a barrel nut of the firearm. Connecting the index block to the handguard generates a continuous clamping action in the handguard which acts through the ribs to apply a radially-directed circumferentially-applied clamping force on a barrel nut through the discrete clamping surfaces. The indexing feature of the index block engages an indexing feature of the upper receiver to ensure proper alignment of the handguard and the upper receiver.

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 practice weapon, having a conventional handle piece with a lock for a drop barrel, with a trigger mechanism which optionally has a rotary bearing for a rotatable trigger, with a spring base on which the return spring is supported; and with a practice breech with a fixed practice barrel. In order to permit a conversion without the use of a tool, an adapter is inserted into the handle piece, the adapter being supported firstly above the trigger mechanism, optionally above the rotary bearing, on a brace and secondly in the upper region of the spring base of the handle piece. Furthermore, the upper region of the adapter has guides for the practice barrel, and the lock interacts with a locking carriage, which is formed in a locking slot of the adapter, in such a manner that the locking carriage secures the practice barrel.

A system for connecting a barrel to an upper receiver of a modular rifle, the upper receiver having an upper receiver extension. The system comprises an upper receiver coupler having a first opening for receiving the upper receiver extension, which is removably secured in the first opening. The system includes a barrel coupler and a gas tube for attaching to a forward segment of the barrel, extending rearwardly along the barrel, passing through a second opening of the barrel coupler and coupled to a gas port that extends from the upper receiver and into the upper receiver coupler. The gas tube is shorter than the barrel. The barrel passes through and is removably secured within a third opening of the barrel coupler; passes through the first opening of the upper receiver coupler and into the upper receiver extension. The upper receiver coupler and the barrel coupler are removably connected.