Smith & Wesson "N" to the largest .44 Magnum type frame. In 2003, the even larger "X" frame was introduced for the .500 S&W Magnum. Most Smith & Wesson revolvers have been equipped with an internal locking mechanism since the acquisition by Saf-T-Hammer. The mechanism is relatively unobtrusive, is activated with a special key, and renders the firearm inoperable. While the lock can simply be left disengaged, most gun enthusiasts prefer "pre-lock" guns. In 1953 the U.S. Army was looking for a pistol to replace the Colt 1911A1. To obtain a bid from the U.S. Government, Smith & Wesson began working on a
Smith & Wesson SD series and the Smith & Wesson M&P design. Smith & Wesson SD The Smith & Wesson SD, formerly known as the Sigma, was Smith & Wesson's first venture into using synthetic materials in pistol construction, using high-strength polymer material for the frame. The pistol is similar to a Glock safe-action pistol in both its design and operation, leading to some controversy and speculation as to the legality of the pistol's patents. Created in 1994, the Sigma incorporates pre-set striker firing mechanism. It is available in both .40 S&W cartridge and 9×19mm Parabellum being one of the first pistols purpose-designed to