The Smith & Wesson Sigma is a polymer-framed, short recoil operated, semi-automatic pistol introduced in 1993 by the American company Smith & Wesson. It was created in 1994, incorporating either a self-cocking or double-action only firing mechanism, doing so allows the shooter to fire without delay and/or preparation. In 1999, Smith & Wesson improved the Sigma series by shortening the barrel and slide, made the grip more ergonomic and comfortable, and slightly enlarging the ejection port.