I have loaded 357 Sig in the past, but abandoned it because it is a pain. I did have alot of fun with 90 grain bullets going very very fast

I used both RCBS and hornady dies and found that the cartrige headspaced on the shoulder, and not the case mouth, with once-fired brass anyway. I also learned that 9mm bullets vary in diameter. Noslers, for example, measure .354" and Speers .356". This is important as far as bullet setback is concerned because the expander plug is fixed in diameter. Noslers suffered alot of setback. Speers suffered no setback. I also found that nickle-plated cases held-on to the bullets much better than plain brass. I used .40 S&W brass to make 357 Sig cases, but abandoned that practice because I found the longer 357 neck more desirable in terms of neck tension.
90gr. Gold Dots at 1800 FPS from a 6" KKM Glock 24 barrel were a blast. What a useless load, though.