A semi-automatic or automatic rifle comprising a barrel attached to and upper receiver and including a compressible bolt carrier extension system. The compressible bolt carrier extension system includes a bolt carrier, an extension spring, two pins, and a reciprocation bolt carrier extension piece. As a whole, the compressible bolt carrier extension system makes possible the use of elongated upper and lower receivers to be used for chambering long-action or other center fire cartridges for use with AR rifles such as the M-16, and M4 etc., eliminating the need for any buffer or buffer tubes other than those commercially available. A further advantage of the compressible bolt carrier extension system is the reduction of felt recoil as the system fully loads during the recoil stroke as it pushes against the buffer absorbing additional recoil energy. The system can be incorporated into firearms using a variety of cartridges.

A firearm accessory mount is an apparatus that maximizes the mounting surfaces on a firearm while allowing the interchangeability of a barrel onto and off of the firearm. The apparatus includes a left tactical rail, a right tactical rail, a gas-cylinder clamp, an upper tactical rail, and an elongated fixture with a transversal arc-shaped cross section. The left tactical rail, the right tactical rail, and the upper tactical rail allows for a variety of firearm accessories to mount onto the apparatus. The gas-cylinder clamp attaches the apparatus onto the gas cylinder. The elongated fixture braces the barrel while attached to the firearm. The arc-shaped cross-section of the elongated fixture allows the barrel to be replaced or a new barrel to be attached without altering the position and orientation of the firearm. The apparatus further includes a lower tactical rail that allows the mounting of firearm accessories beneath the gas cylinder.

A firearm accessory mount is an apparatus that maximizes the mounting surfaces on a firearm while allowing the interchangeability of a barrel onto and off of the firearm. The apparatus includes a left tactical rail, a right tactical rail, a gas-cylinder clamp, an upper tactical rail, and an elongated fixture with a transversal arc-shaped cross section. The left tactical rail, the right tactical rail, and the upper tactical rail allows for a variety of firearm accessories to mount onto the apparatus. The gas-cylinder clamp attaches the apparatus onto the gas cylinder. The elongated fixture braces the barrel while attached to the firearm. The arc-shaped cross-section of the elongated fixture allows the barrel to be replaced or a new barrel to be attached without altering the position and orientation of the firearm. The apparatus further includes a lower tactical rail that allows the mounting of firearm accessories beneath the gas cylinder.

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.

An upper receiver and barrel assembly includes an upper receiver, a barrel assembly and a gas piston assembly. An upper receiver housing receives a shotgun shell cartridge and the bolt carrier group includes a bolt carrier, a bolt within the bolt carrier, a firing pin and an ejector pin to expel fired shells. The barrel assembly includes a barrel, a barrel extension and a barrel nut to secure the barrel and barrel extension to the upper receiver housing. The gas piston assembly includes a piston body, a piston end cap and a piston bonnet configured to slidably receive the piston end cap therein. A piston gap is defined between the piston end cap and the bonnet end wall. The barrel defines a gas port fluidly connecting the open bore of the barrel with the piston gap. A biasing member urges the piston toward the bonnet.

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 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 quick release gas block securing system is provided. The quick release gas block securing system quickly secures the gas block and a gas nozzle attached thereto to a rifle barrel, and conversely, quickly releases the gas block and gas nozzle attached thereto from the rifle barrel.

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.