An advanced gas piston operating system for Armalite Rifle (AR) and Armalite Rifle variants. The advanced gas piston system may include a barrel having a gas port formed through the barrel wall, a gas block assembly, a gas piston assembly, and upper receiver assembly, a sending block, rack and gear assembly, and a bolt carrier assembly with an attached rack. In such a system, a portion of the combustion gases from a fired projectile travel through a gas port in the barrel into a gas block assembly which drives a piston forward which compresses a main spring on an attached rod. The opposite end of the rod is attached to a sending block rack and gear assembly with the gear rotatably engaged with the teeth of another rack that is attached to the bolt carrier assembly. As the gas piston assembly moves forward, the bolt carrier assembly moves rearward until the main spring is fully compressed. Decompression of the main spring returns bolt carrier assembly forward loading the next round into the chamber.

A bolt assembly for a rimmed-cartridge firearm has a bolt head on a forward end. An extractor is located on the bolt head and engages at least a portion of a rim of a rimmed cartridge without engaging a front surface of the rim. A biased tensioner is also located on the bolt head and angularly spaced about the bolt head from the extractor, the tensioner applying force to the rim without engaging a front surface of the rim. The extractor and tensioner cooperate for retaining the rim adjacent the bolt head.

A bolt assembly for a rimmed-cartridge firearm has a bolt head on a forward end. An extractor is located on the bolt head and engages at least a portion of a rim of a rimmed cartridge without engaging a front surface of the rim. A biased tensioner is also located on the bolt head and angularly spaced about the bolt head from the extractor, the tensioner applying force to the rim without engaging a front surface of the rim. The extractor and tensioner cooperate for retaining the rim adjacent the bolt head.

Firearms and bolt mechanisms are disclosed herein. The firearm can include a bolt assembly configured to provide leverage for extracting a cartridge. The bolt body can include a main cylindrical body, handle, and a pivot pin extending through a portion of the handle within the cylindrical body. The handle can be rotated relative to the main cylindrical body to push the bolt assembly along an internal passageway of the receiver.

A firearm with a cartridge has a barrel with an inside surface, a barrel length that is measured starting from a chamber to a barrel muzzle, and a barrel shaft, wherein the cartridge has a single, sabot-free projectile with a peripheral surface. A gap that is open end-to-end in the direction of the barrel shaft is present along at least 90% of the barrel length and over at least 90% of the circumference of the projectile between the peripheral surface of the projectile and the inside surface of the barrel.

A firearm with a cartridge has a barrel with an inside surface, a barrel length that is measured starting from a chamber to a barrel muzzle, and a barrel shaft, wherein the cartridge has a single, sabot-free projectile with a peripheral surface. A gap that is open end-to-end in the direction of the barrel shaft is present along at least 90% of the barrel length and over at least 90% of the circumference of the projectile between the peripheral surface of the projectile and the inside surface of the barrel.

A break open rifle and bolt action rifle having a barrel extension with a breech end for receiving a propellant charge, a muzzle end with an extended attachment structure for receiving a complementary attachment structure of a barrel, and a chamber disposed within and through the barrel extension having a first diameter at a first end and a narrowing portion adjacent a second end opposite the first end, the narrowing portion having a second diameter smaller than the first diameter, wherein the first diameter of the chamber is sized to receive the propellant charge therein, and the second diameter of the narrowing portion is sized to prevent the propellant charge from being further inserted past the narrowing portion, and to prevent a projectile from being inserted through the chamber from the barrel muzzle end. A bolt action configuration having dual diameter non-rotating bolt with an extractor and ejector mechanism for removing a propellant charge.

An improved bolt and bolt carrier with integral gas key having an extension nozzle threadedly secured and pinned to the gas key for use with a direct gas operated firearm is provided. The extension nozzle is designed to receive a portion of the host firearms gas operating system. The firing pin retaining pin is oriented so as to expose its widest profile to the firing pins annular flange, increasing its service life. The bolt has a plurality of lugs extending from its forward end and an extractor recess. The extractor recess is constructed to accommodate an enlarged extractor claw while not undercutting the bolt lugs adjacent thereto. The extractor engages approximately 57% more of a seated ammunition cartridges rim as compared to some prior art AR15/M16 type extractors used with automatic firearms chambered in 6.8 SPC. The result is an improved bolt and bolt carrier which provides for increased operational reliability.

An improved bolt and bolt carrier with integral gas key having an extension nozzle threadedly secured and pinned to the gas key for use with a direct gas operated firearm is provided. The extension nozzle is designed to receive a portion of the host firearms gas operating system. The firing pin retaining pin is oriented so as to expose its widest profile to the firing pins annular flange, increasing its service life. The bolt has a plurality of lugs extending from its forward end and an extractor recess. The extractor recess is constructed to accommodate an enlarged extractor claw while not undercutting the bolt lugs adjacent thereto. The extractor engages approximately 57% more of a seated ammunition cartridges rim as compared to some prior art AR15/M16 type extractors used with automatic firearms chambered in 6.8 SPC. The result is an improved bolt and bolt carrier which provides for increased operational reliability.

A configurable blowback bolt system is provided. Embodiments include a two-part configurable bolt assembly having a bolt carrier and a configurable bolt that allows for use with various calibers of ammunition, both rifle and pistol. The configurable bolt may also eject cartridges to the right or left side of the rifle by moving the extractor to one or the other side of the bolt. A buffer may be included as part of the configurable blowback bolt to shorten the stroke based on the caliber of ammunition being fired with the configurable blowback bolt system.