and .22 LR compared.]] For the rock band of the same name, see 38 Special . .38 Special (pronounced "Thirty-eight Special") is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although semi-automatic pistol and some carbines also use this round. The .38 Special was the standard service cartridge of most police departments in the United States from the 1920s to the 1980s. In other parts of the world, particularly Europe, it is known by its metric designation 9x29mmR. History Despite its name, its caliber is actually .357?.358 inches (9.0678 mm), with the ".38" referring to the approximate diameter of the loaded brass case. This came about because the original .38-caliber cartridge, the .38 Short Colt, was designed for use in converted .36-caliber cap-and-ball (muzzleloading) Navy revolvers, which had cylindrical firing chambers of approximately .374