Provided is a retrofittable adjustable gas valve for an AK-pattern firearm having a standard gas block that receives a head portion of a gas piston. The gas valve includes a valve body configured to be at least partially received by a piston head-receiving portion of a standard AK-pattern gas block and has a gas passageway through it. A threaded adjustment valve member in the valve body has a stem portion configured to adjust gas flow through the gas passageway.

A bolt may be provided for a bolt carrier. The bolt carrier may comprise a gas inlet, a gas expansion chamber, a bolt bore, and the bolt. The gas expansion chamber that may receive a pressurized gas from the gas inlet. The bolt may be disposed in the bolt bore in the bolt carrier. The bolt may comprise a gas ring groove, a gas ring assembly disposed in the gas ring groove, and at least one gas port. The gas ring assembly may be adjacent to the bolt bore. The at least one gas port may provide a pathway for the pressurized gas from the gas expansion chamber to a volume underneath the gas ring assembly to increase a radial sealing force between the gas ring assembly and the bolt bore.

A bolt may be provided for a bolt carrier. The bolt carrier may comprise a gas inlet, a gas expansion chamber, a bolt bore, and the bolt. The gas expansion chamber that may receive a pressurized gas from the gas inlet. The bolt may be disposed in the bolt bore in the bolt carrier. The bolt may comprise a gas ring groove, a gas ring assembly disposed in the gas ring groove, and at least one gas port. The gas ring assembly may be adjacent to the bolt bore. The at least one gas port may provide a pathway for the pressurized gas from the gas expansion chamber to a volume underneath the gas ring assembly to increase a radial sealing force between the gas ring assembly and the bolt bore.

A firearm can have a bolt having a plurality of locking lugs that are configured to have a shear area that is larger than that of a standard M16/M4. A bolt carrier can have a bolt that has a double cut cam having an unlocking cam surface that has sufficient dwell increase to delay a start of unlocking when the bolt carrier is used in an M4 carbine. A stepped extractor pin may be provided that prevents disengagement of the extractor pin. A tube can be configured to provide gas from a barrel of the firearm to the piston via the carrier key. The tube can have a heat radiator formed from triangular shaped threads on at least a portion of the tube. A piston on the bolt and can have a plurality of rings including pairs of mating rings that are formed and maintained as a matched pair.

A firearm can have a bolt having a plurality of locking lugs that are configured to have a shear area that is larger than that of a standard M16/M4. A bolt carrier can have a bolt that has a double cut cam having an unlocking cam surface that has sufficient dwell increase to delay a start of unlocking when the bolt carrier is used in an M4 carbine. A stepped extractor pin may be provided that prevents disengagement of the extractor pin. A tube can be configured to provide gas from a barrel of the firearm to the piston via the carrier key. The tube can have a heat radiator formed from triangular shaped threads on at least a portion of the tube. A piston on the bolt and can have a plurality of rings including pairs of mating rings that are formed and maintained as a matched pair.

A rear sight block/barrel assembly for an AK-47 rifle may include a bull barrel and a rear sight block. The bull barrel may include a first portion, a second portion having an outer diameter less than the first portion, and a third portion having an outer diameter less than the second portion. The bull barrel may include a right handed outer diameter threaded portion that extends from the distal end of the bull barrel. The rear sight block may include a body portion including a lower bore configured so the body portion is press fittable onto the second portion of the bull barrel. The body portion may further include a mount portion having a picatinny rail portion and a dovetail portion. The body portion may include a hole for receiving a pin insertable into the hole for securing the gas tube in position relative to the rear sight block.

The present low pressure bolt carrier group is configured to maximize the axial force component, and minimize the radial force component, applied to both the bolt carrier and the bolt under low-pressure gas conditions, so that the two separate with greater acceleration and under greater force than a standard bolt carrier group when firing low-pressure ammunition. Thus, the present low-pressure bolt carrier group effectively and completely ejects the spent case and chambers the next round. These and other benefits are provided by the present low-pressure bolt carrier group comprising one or more of an increased piston bore diameter, an increased piston diameter, an increased flatness of the piston surface in the radial plane, and an increased stroke length of the piston by lengthening the cam pin slot. Therefore, the present low-pressure bolt carrier group solves long-persisting problems with standard bolt carrier groups when using low-pressure rounds.

The present low pressure bolt carrier group is configured to maximize the axial force component, and minimize the radial force component, applied to both the bolt carrier and the bolt under low-pressure gas conditions, so that the two separate with greater acceleration and under greater force than a standard bolt carrier group when firing low-pressure ammunition. Thus, the present low-pressure bolt carrier group effectively and completely ejects the spent case and chambers the next round. These and other benefits are provided by the present low-pressure bolt carrier group comprising one or more of an increased piston bore diameter, an increased piston diameter, an increased flatness of the piston surface in the radial plane, and an increased stroke length of the piston by lengthening the cam pin slot. Therefore, the present low-pressure bolt carrier group solves long-persisting problems with standard bolt carrier groups when using low-pressure rounds.

An improved bolt and bolt carrier with integral gas key having an extension nozzle threadedly secured and pinned to the gas key for use with a direct gas operated firearm is provided. The extension nozzle is designed to receive a portion of the host firearm's gas operating system. The firing pin retaining pin is oriented so as to expose its widest profile to the firing pin's annular flange, increasing its service life. The bolt has a plurality of lugs extending from its forward end. The extractor recess is constructed so that the face of the bolt is round and the adjacent lugs fully supported. The extractor engages approximately 17% more of a seated ammunition cartridge's rim as compared to the prior art AR15/M16 extractor. The result is an improved bolt and bolt carrier which provides for increased operational reliability.

An improved bolt and bolt carrier with integral gas key having an extension nozzle threadedly secured and pinned to the gas key for use with a direct gas operated firearm is provided. The extension nozzle is designed to receive a portion of the host firearm's gas operating system. The firing pin retaining pin is oriented so as to expose its widest profile to the firing pin's annular flange, increasing its service life. The bolt has a plurality of lugs extending from its forward end. The extractor recess is constructed so that the face of the bolt is round and the adjacent lugs fully supported. The extractor engages approximately 17% more of a seated ammunition cartridge's rim as compared to the prior art AR15/M16 extractor. The result is an improved bolt and bolt carrier which provides for increased operational reliability.