A firearm includes a quick-change barrel including: (a) at least two barrel-mounting features, each configured to selectively interact with a barrel-receipt feature of the firearm during mounting of the quick-change barrel to a mounting structure of the firearm, or (b) at least one barrel-mounting feature configured to selectively interact with at least two barrel-receipt features of the firearm during mounting of the quick-change barrel to a mounting structure of the firearm. The barrel is selectively mountable to the firearm in at least two orientations depending, per (a), upon which of the at least two barrel-mounting features interact with the barrel-receipt feature or, per (b), upon which of the at least two barrel-receipt fixtures interact with the barrel-mounting fixture.

There is a multi-caliber weapon system. The multi-caliber weapon system comprises: a frame body, with a front body portion, a middle body portion, and a rear body portion, and including: a plurality of frame flanges, each frame flange being coupled to an interior of the frame body and extending upwardly therefrom; a barrel, removably coupled to the front body portion of the frame body, including: a plurality of barrel rings, each barrel ring being disposed around a circumference of the barrel and spaced along a length of the barrel, wherein the barrel rings are disposed on the frame flanges; a chamber, removably coupled to the middle body portion of the frame body, and removably coupled to the barrel; and a bolt, removably coupled to rear body portion of the frame body, removably coupled to the chamber, and including: a bolt face, removably coupled to a front bolt portion.

A firearm includes a quick-change barrel including: (a) at least two barrel-mounting features, each configured to selectively interact with a barrel-receipt feature of the firearm during mounting of the quick-change barrel to a mounting structure of the firearm, or (b) at least one barrel-mounting feature configured to selectively interact with at least two barrel-receipt features of the firearm during mounting of the quick-change barrel to a mounting structure of the firearm. The barrel is selectively mountable to the firearm in at least two orientations depending, per (a), upon which of the at least two barrel-mounting features interact with the barrel-receipt feature or, per (b), upon which of the at least two barrel-receipt fixtures interact with the barrel-mounting fixture.

A lightweight machine gun receiver has a frame having opposed left and right shell portions configured to separably connect to each other in a connected condition, when in the connected condition, the frame defining an internal space configured to receive a reciprocating bolt, have a barrel connection facility, and have a trigger connection facility, when in the connected condition, the frame being an elongated body having a left side panel having upper and lower edges and an opposed right side panel having upper and lower edges, each of the left and right shell portions having top and bottom spans extending laterally from the associated side panel toward corresponding opposed top and bottom spans, the top and bottom spans having respective free ends having respective top and bottom span mating facilities configured to mate with each other, and the top and bottom span mating facilities each having a sliding interface.

Firearms, particularly rifles, including an upper housing having a barrel, where the barrel and the upper housing are interconnected by means of a guide. In order to improve the connection, the guide includes corresponding prismatic guide surfaces that extend in parallel with the barrel shaft when the firearm is mounted and ready to fire, and the barrel is secured to the upper housing by a tensioning element that can rotate in the upper housing about an axis of rotation that extends normally with respect to the firearm center plane, and the tensioning element includes a tensioning portion and an actuating portion.

A link feed assembly. There is: a bolt carrier near a chamber of a modular weapon system; an infeed ramp, coupled to a first side of a weapon frame near the chamber; an outfeed ramp, coupled to a second side of the capon frame near the chamber and opposite the infeed ramp, positioned to form a space between the infeed ramp and the outfeed ramp; and a feed arm assembly coupled to the weapon frame and extending over the space between the infeed ramp and the outfeed ramp, the feed arm assembly functionally coupled to the bolt carrier such that cycling of the bolt carrier forward and backwards causes cycling of the feed arm assembly in a circuitous motion, the feed arm including a grabbing protrusion that is shaped to grab a top portion of a link during cycling of the feed arm assembly.

A handguard for mounting on a firearm with a housing axis, including: a housing with a slit and with a clamping device including a lever with a center element which lies in a normal plane to the housing axis in a through-opening. It has a recess in its central region, a thread at one end, a lever arm at the other end, and a nut with an internal thread. According to the invention, the center element has a conical nut section. In the assembled state, a nut is screwed onto the thread and thus the center element is arranged in an annular groove of the travelling nut so as to make contact with the center element.

A barrel unit for a firearm, including a barrel with a barrel axis, muzzle and a barrel end opposite the muzzle, on which at least two barrel lugs are formed, and a barrel extension with a barrel receptacle and a first end and a second end, wherein inwardly extending locking lugs are formed on the first end, to work together with a bolt, and inwardly extending barrel locking lugs are formed closer to the second end than the locking lugs. A barrel cam on the outer surface cooperates with a cam lug arranged on the barrel extension to fix the barrel in a predefined end position.

A firearm with a clamping device for attaching a barrel with a barrel extension, where the barrel extension on the one hand, and a seat on the other hand, possibly directly the upper receiver, are connected to one another by means of a clamp and the fixing of the barrel extension on the upper receiver by means of a tension lever that is rotatable about a common axis of rotation running normal to the weapon center plane between two end positions, the ready-to-fire position and the dismantling position, with at least one excentre and a grip and a cam formed on the tension lever.

Adapters for mounting an accessory on a firearm, firearm accessories configured to mount to those adapters, and sheath or handguard assemblies of firearms are disclosed. The recited accessory adapter is substantially annular or tubular in shape, and includes at least two portions that are arranged adjacently along the barrel axis of the firearm. A rear portion is formed on the weapon side of the adapter, so that the rear portion is geometrically complementary to the front end of a firearm sheath, at least in part, and a front portion of the adapter includes a cylindrical coupling surface on the outside for coupling of the accessory, where the coupling surface includes at least one bayonet extension that projects radially outwards.