A firearm includes a receiver, a forearm pivotally attached to a distal end of the receiver, and a barrel having a barrel extension. A proximal end of the barrel and the barrel extension are secured within the forearm such that the barrel and barrel extension are pivotable with the forearm relative to the receiver between a first assembled position and a second folded position. The firearm further includes a locking mechanism for securing the forearm, barrel, and barrel extension to the receiver in the first assembled position. The forearm, barrel, and barrel extension may be secured to the receiver in the first assembled position for use of the firearm, after which the firearm may be folded for storage and/or transportation.

An upper receiver is disclosed. The firearm contains a bolt carrier assembly positioned within the upper receiver, a recoil spring guide rod, wherein the bolt carrier assembly is configured to slide along the recoil spring guide rod between a locked position and an unlocked position, and a first recoil spring, wherein the recoil spring guide rod is positioned within the first recoil spring.

An upper receiver is disclosed. The firearm contains a bolt carrier assembly positioned within the upper receiver, a recoil spring guide rod, wherein the bolt carrier assembly is configured to slide along the recoil spring guide rod between a locked position and an unlocked position, and a first recoil spring, wherein the recoil spring guide rod is positioned within the first recoil spring.

A firearm is disclosed. The firearm contains a lower receiver containing a first opening, wherein the first opening is configured to accommodate a firing mechanism, an upper receiver removably coupled with the lower receiver, a barrel removably coupled with the upper receiver, a bolt carrier assembly positioned within the upper receiver, wherein the bolt carrier assembly is movable between a locked position and an unlocked position, wherein the bolt carrier assembly contains a rear surface, wherein the rear surface of the bolt carrier assembly is positioned between the barrel and the first opening when the bolt carrier assembly is in the locked position.

A firearm is disclosed. The firearm contains a lower receiver containing a first opening, wherein the first opening is configured to accommodate a firing mechanism, an upper receiver removably coupled with the lower receiver, a barrel removably coupled with the upper receiver, a bolt carrier assembly positioned within the upper receiver, wherein the bolt carrier assembly is movable between a locked position and an unlocked position, wherein the bolt carrier assembly contains a rear surface, wherein the rear surface of the bolt carrier assembly is positioned between the barrel and the first opening when the bolt carrier assembly is in the locked position.

The invention relates to a firearm comprising: a housing (1) having a receptacle (2) for several cartridges or for a magazine with cartridges; a barrel unit (3) which is located in the housing (1) and has a barrel (4) and a cartridge chamber (6); a breechblock (8), which can be moved relative to the housing (1) and is biased in the firing direction by means of a return spring (7), for conveying cartridges into the cartridge chamber (6) or cartridge cases to an ejection port; and a gas braking device which is located in the housing (1) and comprises a cylinder (9) which is positioned parallel to the barrel (4) and which is connected to the interior of the barrel (4) via a gas extraction opening (10); and a piston (11) which can be moved inside the cylinder (9) and which is coupled to the breechblock (8). The breechblock (8) is located in a breechblock carrier unit (12) which is located completely inside the housing (1) over the entire movement path while a shot is being fired and during a reloading operation, the breechblock carrier unit (12) comprising the breechblock (8) itself, two connecting sections (13) guided parallel to the barrel (8) in the housing (1), and a coupling section (14) to be coupled with the piston (11) of the gas braking device.