How a Steyr GB works

The Steyr GB is a double-action 9×19mm Parabellum caliber, large-framed semi-automatic pistol employing a gas-delayed blowback action. As such the GB abbreviation stand for Gasbremse (gas brake). The weapon went into general civilian production in 1982, and in 1988 production ceased. It features a unique gas-delayed blowback system based on the Barnitzke system, first used in the Volkssturmgewehr 1-5, and subsequently in the Swiss Pistole 47 W F (Waffenfabrik Bern) prototype pistol. The Barnitzke system uses gas pressure from the ignited cartridge and feeds it through a small port in the barrel in front of the chamber to retard the rearward motion of the slide. This is accomplished by using the fixed piston formed by the outside of the barrel inside a moving cylinder formed by the inside of the slide and gas pressure in the space between them opposing the rearward motion of the slide until the gas pressure has declined (at which point the bullet has left the muzzle) thereby allowing the slide to c