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 Model 645 shooting. Smith & Wesson (S&W) began experiments with .45 ACP-firing pistols in 1984, and produced their first one, the Model 645, in 1985. Public demand led to the development of this series. The series is a .45 ACP version of their 9mm Parabellum weapons. They are normally double-action weapons, or what Smith & Wesson refers to as a traditional double action. They generally have a barrel bushing press fitted into the muzzle end of the slide instead of a separate barrel bushing like a 1911 pistol. Like many Smith & Wesson models, each variant was generally in production for only