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 4506 Smith & Wesson Model 4516: Compact version with a 3 " barrel on a smaller frame accepting 7 round single column magazines. Smith & Wesson Model 4546: Double-action-only version of the 4506 with a rounded, stubby hammer. Only produced in 1992. Smith & Wesson Model 4563: Midsize version with a 4" barrel on a full-size alloy frame. Smith & Wesson Model 4566: Midsize version with a 4" barrel on a full-size steel frame, the 4566 was formerly the issued sidearm of the New Hampshire State Police. Current issue (June 2015) with West Virginia State Police, in DAO (Double-Action-Only; TSW version),