Abstract: A delayed rotary blowback mechanism integrated into a firearm bolt and carrier subassembly. A plurality of radial locking lugs are configured at a rear end of the bolt and seat within a mating profile of a barrel extension of the firearm in a fully chambered position. A plurality of chamfered locations are configured between the lugs and a receiving profile in the barrel extension for influencing linear to rotational motion of the bolt. A cam pin extends upwardly from the bolt and seats through a circumferentially directed slot configured within the bolt carrier. Upon initiating of the discharge cycle, signaled by the round traveling through and out the end of the barrel, the chamfered configuration results in the bolt and cam pin rotating within the carrier and the lugs subsequently separating from the barrel extension, with the bolt and associated carrier retaining sufficient inertia to cycle through the discharge cycle to the set position concurrent with reloading a subsequent cartridge.

Abstract: An auto sear for a firearm having a lower receiver with a trigger, disconnector and hammer, and an upper receiver with a reciprocating bolt carrier group. The sear includes a body pivotally mounted within the lower receiver rearwardly of the trigger, disconnector and hammer. The body includes a forward-most planar shaped portion in which are configured each of lower and upper trip engagement location. Upon the hammer initially striking the firing pin, the bolt carrier subsequently displaces rearwardly following cartridge discharge in order to rotate the hammer downwardly into contact with the lower trip engaging location. Upon a return forward displacement of the bolt carrier, an underside ledge thereof contacts the upper trip engaging location in order to pivot the lower engaging location out of contact with the hammer, permitting the same to rotate back into striking contact with the firing pin.

Abstract: A delayed rotary blowback mechanism integrated into a firearm bolt and carrier subassembly. A plurality of lugs are configured at a rear of the bolt and seat within a mating profile of a barrel extension of the firearm in a fully chambered position. Chamfered locations are configured between the lugs and a receiving profile in the barrel extension for influencing linear to rotational motion of the bolt. A cam pin extends upwardly from the bolt and seats through a circumferentially directed slot configured within the bolt carrier. Upon initiating of the discharge cycle of a fired round traveling out the end of the barrel, the chamfered configuration results in the bolt and cam pin rotating within the carrier and the lugs subsequently separating from the barrel extension. The bolt and carrier retain sufficient inertia to cycle through the discharge cycle concurrent with reloading a subsequent cartridge.

Abstract: A bolt hold open linkage incorporated into a lower receiver of a firearm for elevating a bolt catch into contact with a forwardly displacing bolt associated with an upper receiver reciprocating action assembly. An elongated central stem has a forward end and an opposite rearward end, a shoulder being supported, via an extending portion, from the rearward end. A pair of axially aligning mounting pins are supported at spaced apart locations of the lower receiver above a magazine receiving well incorporated into the lower receiver, the pins mounting the opposite ends in pivoting fashion about a centerline extending between the axially aligning pins which is offset from the shoulder.

Abstract: A bolt hold open (BHOA) catch assembly configured for operating with rimfire ammunition for use with a firearm including a receiver with an exposed receiving chamber. A BHOA housing is supported upon the lower receiver in communication with a receiver chamber in communication with a bolt assembly. A catch is supported in elevatable fashion relative to an end of the actuator housing and an end most and downward extending structural portion of the elevatable catch is capable of being manipulated by an externally configured and toggled bolt catch so that an inner pivoting end portion thereof engages the structural portion to raise the BHOA supported catch into contact with a forwardly traveling bolt, such as upon release of a previously retracted charging handle. The BHOA catch can alternatively be actuated upwardly by a suitably configured follower associated with an attachable and cartridge holding magazine, this again following a last shot hold open protocol.

Abstract: A modularized upper receiver including any number of replaceable panels applied to either the left or right side of the receiver for establishing varying combinations of forward assist and spent shell/gas deflection. The modifiable upper receiver is particularly suited to ambidextrous use and, in the further instance of forward assist notches added to an opposite side of the carrier, prevents the shooter from removing such as the right hand from the pistol grip in order to force feed rounds into the firing chamber.

Abstract: The present invention teaches an insert locking mechanism incorporated into a sub caliber action device, installable within an upper receiver of an AR-15 type firearm, and which interfaces with an upper receiver mounted forward assist for use with such as .22 caliber ammunition and in order to eliminate movement or play of the chamber insert adaptor associated with the substituted sub caliber action. The mechanism includes a generally cylindrical shaped body supported upon the action and exhibiting a plurality of radially projecting and circumferentially extending lugs which are configured to mate and seat within a plurality of grooves circumferentially arrayed within a barrel defined in the upper receiver.

Abstract: A combination magazine and outer skin for a firearm including a magazine core adapted to releasably engage a firearm in communication with an action assembly associated with the firearm. Multiple cores are stackable end-to-end to define a continuous interior, with an end cap engaging an open bottom of a lowermost core. A design indicia exhibits an interior recess and is assembled around the stacked cores. A dual use follower is in use with an uppermost located magazine and maintains the assembly bolt in an open position and following the last cartridge being fired until such time as the magazine is removed. In the further variant, with a BHOA installed in place, the follower activates the BHOA and the bolt to remain in the retracted/open position, following magazine removal.

Abstract: A bolt hold open (BHOA) catch assembly configured for operating with rimfire ammunition for use with a firearm including a receiver with an exposed receiving chamber. A BHOA housing is supported upon the lower receiver in communication with a receiver chamber in communication with a bolt assembly. A catch is supported in elevatable fashion relative to an end of the actuator housing and an end most and downward extending structural portion of the elevatable catch is capable of being manipulated by an externally configured and toggled bolt catch so that an inner pivoting end portion thereof engages the structural portion to raise the BHOA supported catch into contact with a forwardly traveling bolt, such as upon release of a previously retracted charging handle. The BHOA catch can alternatively be actuated upwardly by a suitably configured follower associated with an attachable and cartridge holding magazine, this again following a last shot hold open protocol.

Abstract: A sub caliber action device installable within an upper receiver of an AR-15 type firearm which interfaces with an upper receiver mounted forward assist for use with such as .22 caliber ammunition. The device includes a generally elongated receiver plate exhibiting a generally lengthwise extending notched interior established between extending sides, with the notched interior seating a bolt and a forward assist adaptor in reciprocating fashion along the receiver plate between an end-most location and a forward secured chamber adaptor. The adaptor is reconfigurable to inertially and linearly displace a limited distance relative to the bolt support sleeve during full auto firing mode and which influences the bolt against the chamber adaptor during striking of the bolt supported firing pin by the hammer.

Abstract: A telescopic charging handle incorporated into an upper receiver of an AR-15 type firearm includes a first stem portion integrally formed with a handle shaped head. A second stem portion terminates at a distal end in a projecting beak and is further telescopically engaged at a proximal end to the first stem portion. In this fashion, the charging handle is extended upon being rearwardly displaced in order to accommodate a modified length sub caliber action.

Abstract: A bolt catch assembly configured for operating with rimfire ammunition for use with a firearm including a receiver with an exposed receiving chamber. The assembly includes a bolt catch actuator housing supported in seating fashion relative to the receiving chamber and communicating with an attachable magazine. A catch actuator is supported in elevatable fashion relative to an end of the actuator housing. A bolt catch component and integrally formed actuator catch engaging portion is slaved to the catch actuator in order to be displaced in response to elevating motion exerted upon the catch actuator, such as by a follower component biasingly disposed within the magazine. The follower, in its uppermost displaced position within the attached magazine, engages a tab associated with the catch actuator which extends over a communicating interior of the bolt catch actuator housing in communicating alignment with the exposed receiving chamber.

Abstract: A maintenance kit incorporated into operable components of a sub caliber action device installable within an upper receiver of an AR-15 type firearm for facilitating disassembly, maintenance and reassembly of a bolt and forward chamber adaptor with a receiver plate. The kit includes at least one gauge dimension defined in a barrel of the forward chamber adaptor for establishing a correct spacing between lengthwise extending and interior notch defining arms associated with the receiver plate. A modified guide rod facilitates at least one of disassembly of the bolt firing pin/extractor and cleaning of the chamber adaptor interior prior to reassembly of the bolt and chamber adaptor.

Abstract: A bolt catch assembly for use with a firearm including a receiver with an exposed receiving chamber and an underside engageable magazine. The assembly includes a bolt catch actuator housing supported in seating fashion relative to the receiving chamber and communicating with an attachable magazine. A catch actuator is supported in elevatable fashion relative to an end of the actuator housing. A follower component is upwardly and biasingly disposed within the magazine and which, upon contacting the catch actuator, displaces an associated bolt catch of the firearm in an upper and bolt restraining position.

Abstract: An anti-rotation feature incorporated between a cotter pin and a sub caliber action device installable within an upper receiver of a firearm. A receiver plate exhibits a notched interior for seating a bolt in reciprocating fashion. A chamfer formed in a side of the bolt intersects a length extending channel of the bolt for seating within the notched interior. The chamfer seating a head of the cotter pin to prevent rotation during bolt travel. A rearward support sleeve seats an opposing guide rod associated with the receiver plate and in order to maintain the bolt assembly. A firing pin exhibits a notch at a location along its shaft and, upon installation within an interior aperture of the bolt, is retained in position by the cotter pin. The firing pin is configured so as to exhibit a reduced diameter end projection upon which is supported a coil spring.