Abstract: A sighting system for a firearm and related methods are disclosed. The sighting system has front and rear flip-up sights, wherein the front sight comprises a flip-up portion having an aperture through which a sight post can partially extend; a knob comprising one or more notches on a first side and the sight post extending from a second side; at least one detent arranged to face and interact with the one or more notches. The knob is configured to rotate about a first axis, where the rotation causes the sight post to move in a first direction along the first axis; tilting of the knob in a second direction based on the detent interfacing with the notches; and tilting of the sight post in the second direction, thereby forcing at least a portion of the sight post to press against the aperture, or a combination thereof.

Abstract: This disclosure describes systems, methods, and apparatus for a bipod having pivot and cant functionality built into a unified cant/pivot assembly, housing, and pivot block. Rotation of a locking knob under the housing can gradually increase or decrease friction of the cant and pivoting degrees of freedom. Sufficient loosening of the locking knob can allow a pivot block to be lifted from the housing and rotated 180°, and then retightened to lock in a given pivot position. Before this 180 rotation of the pivot block, the pivot block and hence the firearm is free to pivot up to 10°, or up to 20°, or up to 30°.

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 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: A device may include an elongated body comprising an opening configured to receive a receiver extension tube of a firearm. A device may include a brace body affixed distally to the elongated body and comprising a window configured to receive a clamp mount, wherein the clamp mount is configured to retain the arm brace in a fixed position on the receiver extension tube and comprises: one or more clamps comprising at least one through-hole and one or more pads, wherein the one or more pads are configured to engage with the receiver extension tube via adjustment of one or more fasteners interfacing with the at least one though-hole.

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: 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: 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: 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: Systems, methods, and apparatus are described 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: 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: 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: This disclosure describes systems, methods, and apparatus for a bipod having pivot and cant functionality built into a unified cant/pivot assembly, housing, and pivot block. Rotation of a locking knob under the housing can gradually increase or decrease friction of the cant and pivoting degrees of freedom. Sufficient loosening of the locking knob can allow a pivot block to be lifted from the housing and rotated 180°, and then retightened to lock in a given pivot position. Before this 180 rotation of the pivot block, the pivot block and hence the firearm is free to pivot up to 10°, or up to 20°, or up to 30°.

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: 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.