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 Triple Lock Ejector 3rd Model, but the "Triple Lock" feature was never used again. To cover manufacturing shortages of the Webley Mk VI, early in the war the Ministry of Munitions contracted Colt and Smith & Wesson to manufacture revolvers chambered in .455 Webley. Smith & Wesson were given an initial contract to manufacture 5,000 triple lock pistols, known as the Pistol Smith & Wesson .455 with 61⁄2 inch barrel Mark I, it was introduced into British service as a "substitute standard" sidearm on 5 July 1915 alongside the Colt New Service. Subsequent orders, lacking the third locking lug and ejector shroud,