.500 S&W Magnum

The .500 S&W Magnum is a fifty-caliber semi-rimmed handgun cartridge developed by Cor-Bon in partnership with the Smith & Wesson "X-Gun" engineering team for use in the Smith & Wesson Model 500 X-frame revolver and introduced in February 2003 at the SHOT show. Wikipedia
 
Case length0′ 2″
Rifling twist1:18.75 in (476.25 mm)
Maximum pressure60,000 psi (410 MPa)
Overall length2.300 in (58.4 mm)
Rim diameter.556 in (14.1 mm)
Neck diameter.526 in (13.4 mm)