I have a Dillon 550 and reload most flat sided pistol ammunition. I am having problems finding 357 Sig ammo to buy at reasonable price. What are the best dies, and should I go with carbide? I see dillion dies for around $125. do the cases need to be lubed prior to sizing in Dillion dies? What is a good powder for this cartridge, I current uses Accurate #2, #5 and Win 231, etc.
thanks for any recommendations

I don't load that one but the carbide dies I do not own,never saw the need.Hornady 's are the best dies I own and I have Lee,forester and rcbs.

I do load the 357 Sig and I do use the Dillon carbide dies - I think it is worth the money and saves a lot of potential problems as well as doing a perfect job without lube. That said I do very very lightly spray the cases with Dillon case lube and it make resizing the case much easier. I load on the Dillon 650.

I also use Dillon's 357 Sig carbide sizer in my RCBS Progressive. I lightly hit with Hornady One-shot as well. My powders of choice for 125g at 1300+ fps are VN350 and VN105.

IMO, the Dillon diees are well worth the money. I occasionally only lube nickle cases, brass ones, never.