I'm starting this thread as a catch-all for the basics on this cartridge.
I learned everything I needed here at the forum, but there is a shortage of info.
The primary challenge in reloading for .357 SIG is getting through the neck tension issues and finding good boolits. The bottleneck only has about 3/16" that grip on the boolit, so a boolit with enough of a top driving band, and a short enough nose for the mags is a necessity. Examples of boolits that I have used thus far: Lee 356-120 TC (standard groove), Lee 358-158 RF, Accurate 35-147S. Many folks rely on a full case of slow powder to act as a stop for the boolit, and to ensure that set-back doesn't happen. I prefer to also give each round a good crimp.
Boolits that have been known to work are:
Lee 358-125 RF
Lee TL356-95RF
Lee 358-105 SWC
NOE 357-135RF (Ranch Dog)
Accurate 35-125S (357 SIG nose length)
Accurate 35-147S (" ")
Jax:
Hornady XTP HP 124 and 147
Traditional long-nose 9mm boolits such as NOE's 358-135 RF/128 HP) will likely not function well.
too little upper driving band, too long a nose.
Lets hear from ya 357sig shooters!