Abstract: A multi-caliber ambidextrously controlled firearm that includes an adjustable ejection system to facilitate the ejection of spent cartridge casings from a firearm. The adjustable ejection system includes an ejection port defined by an aperture in the firearm and a deflector. The deflector is attached to the firearm to adjust the size of the ejection port and may be attached at one of at least two attachment positions of the firearm. The adjustable ejector system includes an ejector selectively attached to the firearm at one of at least two ejector attachment positions. The improved firearm also includes an ambidextrous magazine catch system for selectively retaining a magazine within a firearm. The magazine catch system includes a first button opposite a second button such that either button may be actuated by a user to release the magazine retained with the firearm.

Abstract: A firearm including a barrel having a chamber and an integrally formed upper receiver having a passageway, an accessory rail extending the complete length of the upper receiver, and a guidance feature extending along the passageway. The firearm also includes an operating rod having an anti-bounce mechanism, a bolt that is rotated counter-clockwise to lock against the chamber, a bolt carrier having a safety extension disposed below the bolt that prevents a hammer from striking a firing pin until the bolt is locked against the chamber, a lower receiver, a recoil spring assembly, and a fire control group. The bolt includes a polymer spring that biases a sliding extractor against the base of a cartridge. The sliding extractor is disposed at an angle ranging from thirty degrees to fifteen degrees on the bolt face to provide a low ejection angle from the firearm.