I did the same thing with Sig P226 and a SigP239. Both originally came as 40SW, good guns in a good caliber. The Sig 357 Sig barrels dropped right in without any fitting on both guns and shot to POA. Great! Two multi caliber guns. Mags and springs all worked fine. No issues. I reload now for both the 40SW &the 357Sig. Reloading is the best way to go for the 357Sig, otherwise it’s too expensive to shoot on a regular basis. I really like the ability to swap out barrels at the range. Shoot one, change barrels and I’ve got a whole new gun.
