An apparatus and method for modifying a handgun to accept an optical sight comprises a modified slide mechanism adapted to include a flat recessed rear section configured to receive an adapter plate for mounting an optical sight. Various embodiments of the adapter include modified internal components used to replace stock components what will no longer fit within the modified profile of the slide mechanism. Replacement of the slide mechanism and associated internal components will allow a user to add an optical sight to an existing handgun.

A system for firing reduced energy cartridges from a modern sporting rifle utilizes a bolt assembly weighing less than a conventional bolt assembly for such rifles and utilizes blow back for cycling the bolt assembly rather than gas operation. A bolt insert in a polymer bolt carrier of the bolt assembly has a projection that fits within a recess on the rear face of reduced energy cartridges. The reduced energy cartridges having a polymer casing, a rimfire power load for propellant, the power load recessed from the rear face of the casing. Tuning the bolt may comprise adjusting the weight of the bolt or the sliding resistance of the bolt assembly in the upper receiver. The bolt may be formed by metal injection molding with a polymer bolt carrier attached thereto.

A system for firing reduced energy cartridges from a modern sporting rifle utilizes a bolt assembly weighing less than a conventional bolt assembly for such rifles and utilizes blow back for cycling the bolt assembly rather than gas operation. A bolt insert in a polymer bolt carrier of the bolt assembly has a projection that fits within a recess on the rear face of reduced energy cartridges. The reduced energy cartridges having a polymer casing, a rimfire power load for propellant, the power load recessed from the rear face of the casing. Tuning the bolt may comprise adjusting the weight of the bolt or the sliding resistance of the bolt assembly in the upper receiver. The bolt may be formed by metal injection molding with a polymer bolt carrier attached thereto.

A gas-delayed blowback firearm includes a lower receiver and an upper receiver releasably coupled thereto. A barrel having a cartridge chamber, an axial bore, and a barrel gas port is secured to the upper receiver. A bolt assembly in the upper receiver reciprocates between a forward in-battery position and a rearward position. A timing block is secured to the bolt assembly. A cylinder housing with an internal gas chamber and a cylinder gas port is secured to the upper receiver. A gas passageway fluidly communicates the barrel gas port with the cylinder gas port. A plunger in the gas chamber is secured to the timing block. The plunger reciprocates with the bolt assembly. Discharge of a cartridge received in the cartridge chamber temporarily pressurizes the gas chamber, applying a forward force to the plunger which causes the plunger to delay rearward travel of the bolt assembly.

A gas-delayed blowback firearm includes a lower receiver and an upper receiver releasably coupled thereto. A barrel having a cartridge chamber, an axial bore, and a barrel gas port is secured to the upper receiver. A bolt assembly in the upper receiver reciprocates between a forward in-battery position and a rearward position. A timing block is secured to the bolt assembly. A cylinder housing with an internal gas chamber and a cylinder gas port is secured to the upper receiver. A gas passageway fluidly communicates the barrel gas port with the cylinder gas port. A plunger in the gas chamber is secured to the timing block. The plunger reciprocates with the bolt assembly. Discharge of a cartridge received in the cartridge chamber temporarily pressurizes the gas chamber, applying a forward force to the plunger which causes the plunger to delay rearward travel of the bolt assembly.

The present disclosure provides ammunition magazines and hold-open bolt carriers for using low-cost (e.g., 22LR) ammunition in a standard AR-15 or M16 upper receiver.

A gas-delayed blowback firearm includes a lower receiver and an upper receiver releasably coupled thereto. A barrel having a cartridge chamber, an axial bore, and a barrel gas port is secured to the upper receiver. A bolt assembly in the upper receiver reciprocates between a forward in-battery position and a rearward position. A timing block is secured to the bolt assembly. A cylinder housing with an internal gas chamber and a cylinder gas port is secured to the upper receiver. A gas passageway fluidly communicates the barrel gas port with the cylinder gas port. A plunger in the gas chamber is secured to the timing block. The plunger reciprocates with the bolt assembly. Discharge of a cartridge received in the cartridge chamber temporarily pressurizes the gas chamber, applying a forward force to the plunger which causes the plunger to delay rearward travel of the bolt assembly.

A gas-delayed blowback firearm includes a lower receiver and an upper receiver releasably coupled thereto. A barrel having a cartridge chamber, an axial bore, and a barrel gas port is secured to the upper receiver. A bolt assembly in the upper receiver reciprocates between a forward in-battery position and a rearward position. A timing block is secured to the bolt assembly. A cylinder housing with an internal gas chamber and a cylinder gas port is secured to the upper receiver. A gas passageway fluidly communicates the barrel gas port with the cylinder gas port. A plunger in the gas chamber is secured to the timing block. The plunger reciprocates with the bolt assembly. Discharge of a cartridge received in the cartridge chamber temporarily pressurizes the gas chamber, applying a forward force to the plunger which causes the plunger to delay rearward travel of the bolt assembly.

In the fixed frame it has a base, in which a barrel with the axis below the level of the upper edge of the shooter's hand, a trigger, a buffer and a long ejector are attached. A pistol grip with a cartridge magazine is obliquely slid into the frame and attached. A semi-embedded moving slide, containing especially a closed launch pad, a firing pin, an obliquely placed extractor and a rob of the trigger mechanism, is inserted into the frame from above. The slide is covered from above by upper body attached to the barrel and at two points to the frame, which carries sights at the top and has elements of the hammer system placed on the lower side.

In the fixed frame it has a base, in which a barrel with the axis below the level of the upper edge of the shooter's hand, a trigger, a buffer and a long ejector are attached. A pistol grip with a cartridge magazine is obliquely slid into the frame and attached. A semi-embedded moving slide, containing especially a closed launch pad, a firing pin, an obliquely placed extractor and a rob of the trigger mechanism, is inserted into the frame from above. The slide is covered from above by upper body attached to the barrel and at two points to the frame, which carries sights at the top and has elements of the hammer system placed on the lower side.