.357 Magnum Brass

The .357 Smith & Wesson Magnum, .357 S&W Magnum, .357 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,^[2] and Douglas B. Wesson^[2]^[3] of firearm manufacturers Smith & Wesson and Winchester.^[4]^[5] The .357 Magnum cartridge is notable for its highly effective terminal ballistics.

The .357 Magnum 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.^[6] The "Magnum era" began with the .375 H&H rifle cartridge, spreading to handguns with the .357 Magnum.

Source: https://en.wikipedia.org/wiki/.357_Magnum