Provided is an external piston gas-operated firearm with an adjustable gas flow. A gas piston is operably connected to a bolt carrier. A gas block has an internal cylinder configured to receive a head portion of the gas piston and the cylinder is operably connected to a barrel bore to allow propellant gas pressure to bear against a face of the piston head portion. The gas piston includes at least one axially selectively positionable exhaust port such that in a first axial orientation no gas is vented through the exhaust port and in a second axial orientation a portion of the gas pressure is exhausted in conjunction with displacement of the piston to cycle the action.

Provided is an external piston gas-operated firearm with an adjustable gas flow. A gas piston is operably connected to a bolt carrier. A gas block has an internal cylinder configured to receive a head portion of the gas piston and the cylinder is operably connected to a barrel bore to allow propellant gas pressure to bear against a face of the piston head portion. The gas piston includes at least one axially selectively positionable exhaust port such that in a first axial orientation no gas is vented through the exhaust port and in a second axial orientation a portion of the gas pressure is exhausted in conjunction with displacement of the piston to cycle the action.

A gas block system including at least some of a firearm barrel having a barrel conical shoulder, wherein a threaded gas block attachment area is formed proximate a gas block attachment area of the barrel, and wherein a barrel gas port is formed within at least a portion of the gas block attachment area of the barrel; a gas block having a gas block barrel borehole with a tapered proximal shoulder and a tapered distal shoulder, the gas block having a gas block gas port; and a gas block nut having a threaded gas block nut aperture portion and a tapered extension portion extending from the gas block nut, wherein the gas block nut is configured to secure the gas block to the barrel such that the tapered proximal shoulder is abutted against the barrel conical shoulder and the tapered distal shoulder is abutted against the tapered extension portion.

A gas block system including at least some of a firearm barrel having a barrel conical shoulder, wherein a threaded gas block attachment area is formed proximate a gas block attachment area of the barrel, and wherein a barrel gas port is formed within at least a portion of the gas block attachment area of the barrel; a gas block having a gas block barrel borehole with a tapered proximal shoulder and a tapered distal shoulder, the gas block having a gas block gas port; and a gas block nut having a threaded gas block nut aperture portion and a tapered extension portion extending from the gas block nut, wherein the gas block nut is configured to secure the gas block to the barrel such that the tapered proximal shoulder is abutted against the barrel conical shoulder and the tapered distal shoulder is abutted against the tapered extension portion.

An adjustable gas block may include an ingress port to receive gas expelled from a gas port located on a firearm barrel, and a front end to receive a gas metering screw, wherein the gas metering screw is drivable into a threaded hole in the front end to at least partially cover the ingress port with an end of the gas metering screw to restrict a flow of the gas, according to various embodiments. In some embodiments, a columnar sidewall of the head of the gas metering screw may include a circumferential marking alignable with an alignment feature of the front end of the adjustable firearm gas block to set a predefined gas flow restriction. In some embodiments, the adjustable gas block may include a columnar projection with a section alignable with an individual one of the indentations or bumps to preserve a rotational position of the gas metering screw.

An adjustable gas block may include an ingress port to receive gas expelled from a gas port located on a firearm barrel, and a front end to receive a gas metering screw, wherein the gas metering screw is drivable into a threaded hole in the front end to at least partially cover the ingress port with an end of the gas metering screw to restrict a flow of the gas, according to various embodiments. In some embodiments, a columnar sidewall of the head of the gas metering screw may include a circumferential marking alignable with an alignment feature of the front end of the adjustable firearm gas block to set a predefined gas flow restriction. In some embodiments, the adjustable gas block may include a columnar projection with a section alignable with an individual one of the indentations or bumps to preserve a rotational position of the gas metering screw.

In some embodiments, a firearm action mechanism comprises a bolt assembly, a counterweight and a connector engaged with the bolt assembly and with the counterweight. The bolt assembly is arranged to move along a first axis. The counterweight is arranged to move along a second axis. A direction of movement of the bolt assembly is different from a direction of movement of the counterweight. In some embodiments, the movement of the counterweight is opposite the movement of the bolt assembly. In some embodiments, the connector comprises a roller.

In some embodiments, a firearm action mechanism comprises a bolt assembly, a counterweight and a connector engaged with the bolt assembly and with the counterweight. The bolt assembly is arranged to move along a first axis. The counterweight is arranged to move along a second axis. A direction of movement of the bolt assembly is different from a direction of movement of the counterweight. In some embodiments, the movement of the counterweight is opposite the movement of the bolt assembly. In some embodiments, the connector comprises a roller.

A semiautomatic shotgun comprising a receiver, a barrel, a forward gas block assembly attached to the barrel, a slider assembly rearward of the gas block assembly extending into the receiver. Upon firing a shotshell the explosive gases in the barrel are diverted through two ports into the gas block assembly, specifically into a pair of lateral pressure relief valves positioned on both sides of the barrel. The pressure relief valves further having a gas pathway to a piston chamber. A piston is forced rearwardly and engages a slider of the slider assembly that is linked to a breech block in the receiver. The breech block loads unfired shells and ejects the fired shells accomplishing the semiautomatic recycling. The dual pressure relief valves actuate to moderate and limit the gas pressure that enters the piston chamber when using shotshells of different power levels thereby providing consistency in the recycling operation.

A semiautomatic shotgun comprising a receiver, a barrel, a forward gas block assembly attached to the barrel, a slider assembly rearward of the gas block assembly extending into the receiver. Upon firing a shotshell the explosive gases in the barrel are diverted through two ports into the gas block assembly, specifically into a pair of lateral pressure relief valves positioned on both sides of the barrel. The pressure relief valves further having a gas pathway to a piston chamber. A piston is forced rearwardly and engages a slider of the slider assembly that is linked to a breech block in the receiver. The breech block loads unfired shells and ejects the fired shells accomplishing the semiautomatic recycling. The dual pressure relief valves actuate to moderate and limit the gas pressure that enters the piston chamber when using shotshells of different power levels thereby providing consistency in the recycling operation.