The M9 handgun, formally Pistol, Semiautomatic, 9mm, M9, is a 9x19mm Parabellum pistol of the U.S. military adopted in the 1980s. It is essentially a mil-spec Beretta 92F, later the 92FS. A locked breech, semi-automatic, single-action / double-action recoil-operated pistol, the M9 uses a 15-round staggered magazine with a reversible magazine release button that can be positioned for either right- or left-handed shooters.