.357 Sig was developed by necking down the .40 S&W cartridge to .357 diameter. It is a semi-automatic pistol bullet unsuitable for the Ruger (or any other .357/38 special) revolver. Stick with 38 special or .357 magnum ammunition for your revolver. Happy New Year & safe shooting.
Vigilantibus et non dormientibus jura subveniunt. Molon Labe!