I have a 226 that was .357 Sig.
My department changed policy and decided to not support .357 Sig. (Department issue ammo was required for all duty and off duty ammo, and they didn't want to carry as many calibers as they had been) I got a Bar-Sto conversion barrel, about $220, 9mm magazines, and changed the recoil spring. Carried it that way for about four years before I retired. Never had a malfunction or any trouble of any kind. It is a soft shooter and I gained a couple rounds of capacity, 15 vs 12 round magazines. The gun is still set up as a 9mm, Although I could switch it back any time, just by changing barrel and recoil spring, and mags.
I also switched a P239 to 9mm, worked the same, but I was able to use the .357 Sig mags. Both guns were absolutely reliable.
It can be done.