.357 SIG - Cartridge Dimensions

Cartridge Dimensions

The .357 SIG has 1.27 ml (19.5 grains) H₂O cartridge case capacity.

.357 SIG maximum C.I.P. cartridge dimensions. All sizes in millimeters (mm).

Americans would define the shoulder angle at alpha/2=18 degrees. The common rifling twist rate for this cartridge is 406 mm (1 in 16 in), 6 grooves, Ø lands=8.71 mm, Ø grooves=9.02 mm, land width=2.69 mm and the primer type is small pistol.

Several sources have published contradicting information regarding .357 SIG headspacing. This is due to originally designed as .357 (9.02mm)round but has been rapidly adapted to .355 (9mm) bullet. According to the official C.I.P. (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portatives) 2007 guidelines the .357 SIG headspaces on the shoulder (P2-H1). Some US sources concur this C.I.P. ruling. US reloading supplier Lyman once published the .357 SIG headspaces on the case mouth (H2).

According to the official C.I.P. (Commission Internationale Permanente Pour L'Epreuve Des Armes A Feu Portatives) guidelines the .357 SIG case can handle up to 305 MPa (44,236 psi) piezo pressure. In C.I.P. regulated countries every pistol cartridge combo has to be proofed at 130% of this maximum C.I.P. pressure to certify for sale to consumers.
The SAAMI pressure limit for the .357 SIG is set at 275.80 MPa (40,000 psi), piezo pressure.