Abstract: An interface for coupling a bipod to a sling stud of a firearm forend. The interface can include two pawls that pivot to release or grasp the sling stud. The pawls can be biased upward via a detent that rides within a vertical aperture in a pivot holder. The pivot holder can move up and down within a vertical aperture in a mounting plate of the interface, and via this movement the pawls may be forced open or closed. A bottom surface of one or both pawls can include an irregular surface different portions of which interface with a top of the detent depending on a vertical position of the pivot holder within the aperture in the mounting plate.

Abstract: This disclosure describes a firearm stock or arm brace with an adjustable length of pull. The stock or arm brace can include a body and lower stock, where the body includes a buffer tube receiving aperture and the lower stock includes a hollow cavity with a plunger and two concentric springs therein. One or more buttons can be affixed to sides of the plunger in the hollow cavity that can be used to depress the plunger against the force of one or both of the springs. One of the two springs may be shorter than the other and have a greater spring constant than the longer spring. Depressing the plunger against the taller spring may allow a user to adjust the length of pull while greater pressure and engagement of the second spring allows the stock or arm brace to be removed from a buffer tube or receiver extension.

Abstract: The present disclosure describes a foldable firearm that collapses into a folded state under spring pressure. The foldable firearm may include a foldable grip assembly. The foldable grip assembly may include a foldable pistol grip, a foldable trigger assembly, a folding bar, and a foldable hand stop. The foldable grip assembly may fold into the top shell of the foldable firearm. The foldable firearm may also include an ambidextrous charging handle assembly that may include a bottom portion, a top portion, a guide bar, and two opposing charging handles. The charging handles may be pulled to unfold the foldable firearm, and/or butterflied such that pivoting one charging handle causes the other charging handle to pivot. The first-pivoted charging handle may then be pulled rearwards to unfold the firearm. The first-pivoted charging handle may then be pulled further rearwards to rack the slide of the foldable firearm.

Abstract: A takedown firearm stock and related methods are disclosed. The takedown firearm stock has a buttstock assembly comprising a magazine release; a first accessory mounting interface; a forend assembly comprising a recess for receiving a barrel having a barrel shank, and a release mechanism for removably coupling the forend assembly and the buttstock assembly, and one of: an attachment bracket or a barrel tray configured to support the barrel, the attachment bracket or the barrel tray comprising the first accessory mounting interface. When the forend assembly is coupled to the buttstock assembly in a deployed configuration, the forend assembly releasably couples to the buttstock assembly at a forend-to-stock interface, and when the forend assembly is coupled to the buttstock assembly in a stowed configuration, the forend assembly releasably couples to an underside of the buttstock assembly.

Abstract: A firearm magazine assembly and a related method are disclosed. The follower has a top platform, a proximal end, a distal end, and at least one slider rail on a first side of the follower. At least a portion of the at least one slider rail is at a position that is between and remote from both the proximal end of the follower and the distal end of the follower. The housing is shaped to receive the follower. The housing has a first wall having a first recess for receiving the at least one slider rail, the first recess defined by opposing surfaces. At least a portion of the at least one slider rail is shaped to engage the two opposing surfaces to limit tilt of the follower.

Abstract: This disclosure describes systems, methods, and apparatus for a follower assembly comprising one or more dummy cartridges, the first thereof comprising an angled follower platform that when pressed between the follower spring and a final live cartridge in the magazine, rotates to a first side of the magazine and enhances follower interaction with a slide lock mechanism. The follower platform may also be angled back to front to further enhance this interaction. The follower platform may include a protruding heel extending laterally from a front portion of the first side of the follower platform configured to interface with the slide lock mechanism. A rear stop may extend from a rear portion of the first side and interface with a downward-facing surface of the magazine near the feed end, wherein contact between these two surfaces causes a front end of the first dummy cartridge to rotate upward.

Abstract: This disclosure describes systems, methods, and apparatus for a firearm grip module having a selector track arcing concentrically around a selector lever aperture in one of two walls of the firearm grip module. The selector track can include multiple levels or heights, corresponding to different operating mode positions of the selector lever, where these different heights cause differing resistance to movement of the selector lever, where greater height equals greater resistance. The selector track may also include a safety indentation, a semi-auto indentation, and a full-auto indentation. The track may also include a removable, molded-in stop, between the semi-auto and full-auto indentations, which blocks the selector lever from overtraveling a standard fire position.

Abstract: A magazine assembly for a firearm and a related method are disclosed. The assembly has a magazine housing defining a track, and a follower assembly. The magazine housing is configured to constrain a cartridge as the cartridge is moved within the magazine assembly such that majority of a proximal surface area of the cartridge does not contact the magazine housing, and a distal tip of the cartridge does not contact the magazine housing.

Abstract: This disclosure describes systems, methods, and apparatus for a locking folding knife having a handle lock and a safety switch arranged around and rotatable around a pivot axis of the knife. In an engaged position the switch overlaps at least a portion of the handle lock and prevents it from moving into an unlocked position. A spring, such as a wire form spring, can be arranged within a pocket of the switch, and when the switch is moved between engaged and disengaged positions the spring can be compressed generating a rotational bias on the switch urging the switch toward either the engaged or disengaged position.

Abstract: This disclosure describes systems, methods, and apparatus for detecting and displaying a number of rounds in a firearm magazine comprising a maximum number of N rounds. The magazine may comprise a follower, magnets on the follower, and <N magnetic-field-sensing sensors arranged along a path of the magnets when the follower moves along a length of the magazine, the sensors generating round count data based on a position of the one or more magnets relative to the <N magnetic-field-sensing sensors, and a first substantially flat antenna arranged on an inside of the magazine and configured to wirelessly transmit a round count indication to a second substantially flat antenna on the firearm, the round count indication based on the round count data, the second substantially flat antenna affixed to an inside of a magazine well of the firearm and mostly overlapping with the first substantially flat antenna.

Abstract: An accessory mounting interface for a firearm, and a related method, are disclosed. The interface has a firearm accessory, a first elongated fastener, and a second fastener rotationally mated to the first elongated fastener. The first elongated fastener has right-handed threading and is arranged through a through hole in the firearm accessory with a first end extending below first and second halves of a first slot protrusion of the firearm accessory. The second fastener has a length greater than a width, the length measured along a longitudinal axis of the second fastener, the second fastener having a plurality of straight edges. At least one of the plurality of straight edges prevents the second fastener from rotating further than a closed position when the at least one of the straight edges abuts a sidewall of an elongated slot in the firearm.

Abstract: A firearm accessory attachment system and method are disclosed. The system has a first body having a longitudinal length, a first protrusion coupled to and extending from the first body in a first direction, and a second protrusion coupled to and extending from the first body in the first direction as the first protrusion, the second protrusion is a first longitudinal distance from the first protrusion. The system also has a second body having a third protrusion coupled thereto, the third protrusion extending in the first direction. The second body is slidable relative to the first body. The system is movable between a locked configuration having a first width and an unlocked configuration having a second width, the second width less than the first width, the first and second widths defined by a direction transverse relative to the longitudinal length.

Abstract: The present invention is an ammunition magazine, preferably made of a reinforced polymer, utilizing a structurally enhancing ridge, angular guide rails and a follower made to interface with said guide rails to reduce wobble. The preferred embodiment also features a protective cover that distributes forces from the spring to more structurally sound areas of the magazine, thus reducing feed end splay, and an ammunition indication system comprised of at least one window and a noticeable marker on the follower spring. The follower and magazine casing are also designed to interface to prevent the follower from popping out of the feed end and the floor plate of the magazine utilizes a locking plate and sliding relationship between the floor plate, locking plate and magazine to secure the floor plate onto the magazine casing. The cover features built in tools for, among other things, unloading and disassembling the magazine.