The .357 Sig - in most loadings save the hotter ones from Double Tap et al - runs at similar velocities to what a .357 snub produces (somewhere in the 1200 range). Most commonly encountered with a 125 grain bullet, the .357 Sig seems to enjoy a good reputation in terms of bullet expansion and such. If properly designed .357 Sig bullets will expand at 1200ish fps, there's no reason that .357 magnum bullets won't.