Abstract: 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 laterally pivotable with the forearm relative to the receiver between a first assembled position and a second folded 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.

Abstract: 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 laterally pivotable with the forearm relative to the receiver between a first assembled position and a second folded 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.

Abstract: 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 laterally pivotable with the forearm relative to the receiver between a first assembled position and a second folded 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.

Abstract: 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 laterally pivotable with the forearm relative to the receiver between a first assembled position and a second folded 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.

Abstract: 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.

Abstract: 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.

Abstract: Methods and structures for tightening the fit between upper and lower receiver subassemblies in a firearm comprising the addition of a raised embossment (projecting upward from the surface) on the upper side of a lower receiver walls or the underside of an upper receiver walls near the pivot pin. When the upper and lower receivers are connected by engaging the rear take-down pin the embossment leverages the receivers on the pivot pin to provide a tight fit.

Abstract: A gas cycling firearm comprising a barrel having a breech end, a muzzle end, an inner surface defining a bore having a bore axis, and an outer surface, wherein the muzzle end is spaced a length L from the breech end, the barrel further having a port providing a fluid path between the bore and the outer surface, the port having an axis that intersects the bore axis at a position P from the muzzle end, where P is less than or equal to ? L; and a gas flowpath extending between the gas port and the piston system, the gas flowpath having a length G and a volume V, wherein G is greater than ? L.

Abstract: An adjustable gas valve having an annular body with an inner surface defining a gas chamber and first and second annular end surfaces defining first and second openings of said gas chamber, the gas valve further having outer surface and at least one gas channel extending between the inner surface and the outer surface providing a gas communication path from the outer surface to the gas chamber, wherein said at least one gas channel is orientated to direct fluid egressing from the channel into the chamber along the inner surface. The invention further includes a regulator occupying a portion of the chamber to define a chamber operating volume, the regulator having at least one outer diameter corresponding to an inner diameter of the passage to substantially inhibit gas flow from the pass through the second opening.

Abstract: The invention includes a gas valve having an annular body with an inner surface defining a gas chamber and first and second annular end surfaces defining first and second openings of said gas chamber, the gas valve further having outer surface and at least one gas channel extending between the inner surface and the outer surface providing a gas communication path from the outer surface to the gas chamber, wherein said at least one gas channel is orientated to direct fluid egressing from the channel into the chamber along the inner surface. The invention further includes a regulator occupying a portion of the chamber to define a chamber operating volume and flowrate, the regulator having a at least one outer diameter corresponding to an inner diameter of the passage to substantially inhibit gas flow from passing through the second opening.

Abstract: A gas cycling firearm comprising a barrel having a breech end, a muzzle end, an inner surface defining a bore having a bore axis, and an outer surface, wherein the muzzle end is spaced a length L from the breech end, the barrel further having a port providing a fluid path between the bore and the outer surface, the port having an axis that intersects the bore axis at a position P from the muzzle end, where P is less than or equal to ? L; and a gas flowpath extending between the gas port and the piston system, the gas flowpath having a length G and a volume V, wherein G is greater than ? L.

Abstract: The invention includes a gas valve having an annular body with an inner surface defining a gas chamber and first and second annular end surfaces defining first and second openings of said gas chamber, the gas valve further having outer surface and at least one gas channel extending between the inner surface and the outer surface providing a gas communication path from the outer surface to the gas chamber, wherein said at least one gas channel is orientated to direct fluid egressing from the channel into the chamber along the inner surface. The invention further includes a regulator occupying a portion of the chamber to define a chamber operating volume and flowrate, the regulator having a at least one outer diameter corresponding to an inner diameter of the passage to substantially inhibit gas flow from passing through the second opening.

Abstract: An adjustable gas valve having an annular body with an inner surface defining a gas chamber and first and second annular end surfaces defining first and second openings of said gas chamber, the gas valve further having outer surface and at least one gas channel extending between the inner surface and the outer surface providing a gas communication path from the outer surface to the gas chamber, wherein said at least one gas channel is orientated to direct fluid egressing from the channel into the chamber along the inner surface. The invention further includes a regulator occupying a portion of the chamber to define a chamber operating volume, the regulator having at least one outer diameter corresponding to an inner diameter of the passage to substantially inhibit gas flow from the pass through the second opening.