Calibers .357 Magnum .357 Magnum ammunition Type Handgun Place of origin United States Production history Designer Elmer Keith and Phillip B. Sharpe Designed 1934 Specifications Parent  case .38 Special Case type Rimmed , straight Bullet  diameter .357 in (9.1 mm) Neck diameter .379 in (9.6 mm) Base diameter .379 in (9.6 mm) Rim diameter .440 in (11.2 mm) Rim thickness .060 in (1.5 mm) Case length 1.29 in (33 mm) Overall length 1.59 in