The .357 Sig is based upon the .40 S&W case simply necked down with a short neck and a sharp shoulder. The design purpose was to achieve 357 Magnum revolvers Ballistics from typical semi-automatic pistols. The combination of high pressure, reasonable case capacity and no barrel venting allows this petite cartridge to generate significant ballistics – fully the equal of the 40 S&W in terms of muzzle energy.
This text is based on information from “Cartridges of the
World”, Hodgdon reloading manual, the cartridge designer and/or