A firearm including a receiver, a barrel, a breech bolt assembly, and a trigger assembly. The bolt assembly has a bolt including a body portion, a lug portion, and a firing pin bore. The lug portion includes outward extending lugs, a cartridge recess, and an off-center hole. The bolt assembly also includes an extractor and an ejector pin. At least some of the lugs on the lug portion of the bolt have a tapering outer face so that a rearward face of the respective lug is taller than a forward face of the respective lug. In another aspect, at least some of the lugs on the lug portion of the bolt have tapering side faces so that a rearward face of the respective lug is wider than a forward face of the respective lug.

A firearm including a receiver, a barrel, a breech bolt assembly, and a trigger assembly. The bolt assembly has a bolt including a body portion, a lug portion, and a firing pin bore. The lug portion includes outward extending lugs, a cartridge recess, and an off-center hole. The bolt assembly also includes an extractor and an ejector pin. At least some of the lugs on the lug portion of the bolt have a tapering outer face so that a rearward face of the respective lug is taller than a forward face of the respective lug. In another aspect, at least some of the lugs on the lug portion of the bolt have tapering side faces so that a rearward face of the respective lug is wider than a forward face of the respective lug.

A firearm assembly including a receiver, a barrel, a locking block and a slide configured to provide rapid changing of a barrel of a handgun wherein the barrel may be for an alternate caliber round of ammunition. The locking block is configured to be secured within the receiver and includes an upper surface that has front rise member, a rear rise member and a valley intermediate thereto. The upper surface of the locking block is mateably shaped with the second portion of the barrel, in particular the lower portion thereof. The lower portion includes a front shoulder member, a rear shoulder member and a notch formed therebetween wherein the notch is configured to mateably engage the rear rise member of the locking block. The slide of the present invention includes a void intermediate the sidewall and the extractor housing. A shim is provided to be secured within the void.

Methods, devices and systems are provided for protecting a firearm. The device and system include a protective insert for a rectangular port in a firearm, the port having a length, a width and a vertical thickness. The protective insert comprises a rectangular plate having a top, an underside, two longitudinal sides, and two ends, each longitudinal side and each end having a length sized to allow the plate to freely ride vertically within the thickness of the port. The Protective insert also includes two parallel wing walls, each of the wing walls being perpendicularly attached to the underside of the plate and along a longitudinal side edge of the plate, wherein each wing wall extends beyond both of the plate ends and under the slide when installed. The protective insert fills the port in the slide and rides on, and is held in place, by the barrel when in operation.

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 pistol is provided, on the plastic housing of which a sliding carriage containing the barrel is guided in the longitudinal direction, which housing has a trigger guard at the transition to a grip stock, and in which housing a locking block is arranged; for an especially light embodiment that is simple to manufacture and nevertheless robust, the locking block forms a unit with the guiding elements of the sliding carriage, which unit is arranged in front of the magazine well and extends forward as far as the trigger guard, as a result of which the guide length is shortened. The locking block is fixed in the housing by a front cross pin and a rear cross pin and accommodates a locking bolt approximately over the second cross pin.

A pistol is provided, on the plastic housing of which a sliding carriage containing the barrel is guided in the longitudinal direction, which housing has a trigger guard at the transition to a grip stock, and in which housing a locking block is arranged; for an especially light embodiment that is simple to manufacture and nevertheless robust, the locking block forms a unit with the guiding elements of the sliding carriage, which unit is arranged in front of the magazine well and extends forward as far as the trigger guard, as a result of which the guide length is shortened. The locking block is fixed in the housing by a front cross pin and a rear cross pin and accommodates a locking bolt approximately over the second cross pin.

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.