The .357 Smith & Wesson Magnum, .357 S&W Magnum, or 9×33mmR as it is known in unofficial metric designation, is a smokeless powder cartridge with a .357-inch (9.07 mm) bullet diameter. It was created by Elmer Keith, Phillip B. Sharpe, and Douglas B. Wesson of firearm manufacturers Smith & Wesson and Winchester. The .ITS is notable for its highly effective terminal ballistics.
The cartridge is based upon Smith & Wesson’s earlier .38 Special cartridge. It was introduced in 1935, and its use has since become widespread. This cartridge began the “Magnum era” of handgun ammunition. The “Magnum era” began with the .375 H&H rifle cartridge, spreading to handguns with the ammo
The ammo was collaboratively developed over a period in the early to mid-1930s by a group of individuals in a direct response to Colt’s .38 Super Automatic. At the time, the .38 Super was the only American pistol cartridge capable of defeating automobile cover and the early ballistic vests that were just beginning to emerge in the Interwar period. Tests at the time revealed that those vests defeated any handgun bullet traveling less than about 1,000 feet per second (300 m/s). Colt’s .38 Super Automatic just edged over that velocity and was able to penetrate car doors and vests that bootleggers and gangsters were employing as cover.
Though .38 Special and .357 Magnum would seem to be different diameter chamberings, they are in fact identical, as at 0.357 inches (9.07 mm) they both have the same bullet diameter. The .38 Special nomenclature relates to the previous use of heeled bullets (such as the .38 Short Colt and .38 Long Colt), which were the same diameter as the case. The only external dimensional difference between .