A piston for a gas-operated firearm has an elongated body having a head portion adapted to be closely received in the cylindrical bore for reciprocation within the bore, the head portion having a first side toward a forward direction and a second side toward the rearward direction, the body having an operational facility on the second side adapted to transmit an operating force to the action in response to gas pressure on the first side, and the head portion defining a bypass passage between the first side and the second side. The bypass passage may have an adjustment facility adapted to provide selectable resistance to gas flow through the bypass passage. The adjustment facility may be a movable occlusion element that selectably occludes the bypass passage. The occlusion element may be a threaded element. The occlusion element may be a collar that receives a portion of the body.

A conversion unit for converting an AR-15 style military assault rifle to a submachine gun includes a central assembly having a magazine well and rear barrel mount. The magazine well can be inserted downwardly into the lower receiver of the assault rifle and accommodates magazines for shorter cartridges. The conversion unit also includes a forearm and barrel assembly and an upper receiver with a stabilizing rail. A pressure equalizing gas operating system eliminates the need for a buttstock with recoil spring. An operating rod extends forward from the upper receiver and into the forearm enclosure. The operating rod is attached to the bolt of the submachine gun and engaged with a reciprocating gas cylinder that surrounds the barrel.

The invention relates to a firearm comprising a barrel comprising a gas opening, and a gas system, which gas system comprises a gas block, a gas piston, a force transmitter assembly, an indexing part and an indexing counterpart, gas openings. The gas block is fixedly attached to the barrel and the gas piston is positioned by the indexing part. In the gas system gas is configured to pass through the gas opening of the barrel via the gas openings of the gas system into the gas block and to set the gas piston to movement. In the gas system the gas piston during its movement backwards is configured to close the gas opening of the barrel for a defined time period and the gas piston is not transmitting power/energy from combustion gas to the force transmitter assembly unless the gas opening/-s is/are closed.

The invention relates to a firearm comprising a barrel comprising a gas opening, and a gas system, which gas system comprises a gas block, a gas piston, a force transmitter assembly, an indexing part and an indexing counterpart, gas openings. The gas block is fixedly attached to the barrel and the gas piston is positioned by the indexing part. In the gas system gas is configured to pass through the gas opening of the barrel via the gas openings of the gas system into the gas block and to set the gas piston to movement. In the gas system the gas piston during its movement backwards is configured to close the gas opening of the barrel for a defined time period and the gas piston is not transmitting power/energy from combustion gas to the force transmitter assembly unless the gas opening/-s is/are closed.

A magazine well for a firearm having an angled spine receiving portion. A charging handle for a firearm having latch that extends below a bottom surface of a crossbar. A bolt carrier for a firearm having a pair of vent holes disposed in the indented portion and at least one additional vent hole on indented portion adjacent to the pair of vent holes. A bolt catch for a firearm having a receiving portion curved to match the contours of a human thumb. A scope assembly for a firearm having markers on a scope and amount that correspond to the same radial positions. A bolt for a firearm having a plurality of ribs disposed on a main body and extending from a front end toward a tail portion of the bolt.

A magazine well for a firearm having an angled spine receiving portion. A charging handle for a firearm having latch that extends below a bottom surface of a crossbar. A bolt carrier for a firearm having a pair of vent holes disposed in the indented portion and at least one additional vent hole on indented portion adjacent to the pair of vent holes. A bolt catch for a firearm having a receiving portion curved to match the contours of a human thumb. A scope assembly for a firearm having markers on a scope and amount that correspond to the same radial positions. A bolt for a firearm having a plurality of ribs disposed on a main body and extending from a front end toward a tail portion of the bolt.

A propellant gas energized firearm has a gas supply passage conducting propellant gas from a gas port of a firearm barrel to an actuating chamber of a bolt carrier and bolt group having an actuating chamber. A gas key member is mounted to the bolt carrier and defines a part of the gas supply passage and has an opening intersecting the gas supply passage. A gas adjustment member is selectively moveable within the gas adjustment opening and has a gas interruption member projecting into the gas supply passage. The gas adjustment member is rotatable within the gas adjustment opening for selectively positioning the gas interruption member within the gas supply passage to selectively control the characteristics of the propellant gas delivery to the actuating chamber of the bolt carrier and bolt group.

A propellant gas energized firearm has a gas supply passage conducting propellant gas from a gas port of a firearm barrel to an actuating chamber of a bolt carrier and bolt group having an actuating chamber. A gas key member is mounted to the bolt carrier and defines a part of the gas supply passage and has an opening intersecting the gas supply passage. A gas adjustment member is selectively moveable within the gas adjustment opening and has a gas interruption member projecting into the gas supply passage. The gas adjustment member is rotatable within the gas adjustment opening for selectively positioning the gas interruption member within the gas supply passage to selectively control the characteristics of the propellant gas delivery to the actuating chamber of the bolt carrier and bolt group.

A fully automatic handgun has a barrel and a blowback, open bolt firing breech mechanism, which is mounted in a displaceable manner on a guide. The breech mechanism has a slide with a substantially U-shaped bracket, on which a breechblock is arranged. The slide is displaceably mounted on the guide and on the barrel.

A fully automatic handgun has a barrel and a blowback, open bolt firing breech mechanism, which is mounted in a displaceable manner on a guide. The breech mechanism has a slide with a substantially U-shaped bracket, on which a breechblock is arranged. The slide is displaceably mounted on the guide and on the barrel.