Abstract: A firearm sight assembly comprises a rear base. The firearm sight assembly comprises a rear sight element movable with respect to the rear base between a lowered condition and an elevated condition. The rear sight element has a first pair of upwardly projecting first rear posts defining a first notch therebetween when in the lowered condition. The rear sight element has a second pair of upwardly projecting second rear posts defining a second notch therebetween when in the elevated condition. The first rear posts extend to a first height above the rear base, and the second rear posts extend to a second height above the rear base. The second height is greater than the first height.

Abstract: Provided is a modular adapter for a firearm receiver that has a standardized threaded socket for mounting a tubular extension or stock support. The adapter includes a base plug configured to threadably engage the threaded socket of a receiver and a modular adaption element attached to the base plug and against a rear surface of the receiver. The adaption element presents an attachment means for attaching an accessory, such as a stock, to the adaption element.

Abstract: 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.

Abstract: A firearm sight assembly comprises a rear base. The firearm sight assembly comprises a rear sight element movable with respect to the rear base between a lowered condition and an elevated condition. The rear sight element has a first pair of upwardly projecting first rear posts defining a first notch therebetween when in the lowered condition. The rear sight element has a second pair of upwardly projecting second rear posts defining a second notch therebetween when in the elevated condition. The first rear posts extend to a first height above the rear base, and the second rear posts extend to a second height above the rear base. The second height is greater than the first height.

Abstract: 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.

Abstract: Firearm pin retainer plates and pins have a frame defining an internal space, a moving action part defining a bore and connected to the frame within the space, a pivot pin connected to the frame and to the action part such that the action part pivots with respect to the frame, the pivot pin having a cylindrical body portion closely received in the bore and defining a pin axis, the pivot pin having a first flat surface portion, a retention element connected to the frame within the space and having a first retention facility adapted to engage the first flat surface portion to prevent rotation of the pin with respect to the frame. The pin may have a second flat surface portion opposed to the first flat surface portion. The first retention facility may define a slot having opposed edges operable to engage the first and second flat surface portions.