I'm loading 357 Sig on my Dillon 550B. Using Redding die set + their taper crimp die. You have to lightly lube the brass before resizing - I'm using Dillon lube - put 75-100 pieces of brass in shoe box, spray very lightly, shake box & repeat. To de-lube finished ammo tumble in corncob for ~10 minutes.
You have to be selective about the bullets you choose to load. I've had best results with Hornady 115 & 124gr XTP's. Crimping is very important as is brass length. I'm using Starline brass & have not had any problems.
I've used AA#7, #9 & V-V 3N37 powders w/ good results. Just recently purchased some Vectan SP2 - not tried it yet but it should work good.
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...... bk40