I bought a used P226 about 10-12 years ago in .357Sig and bought a .40S&W barrel for it. I shot less than 50 rounds of .357Sig and then changed out the barrel to the .40 and never looked back.
As you probably already have seen the mags will say .357 and .40.
Most people go the other way.
At the time when I was buying there were a buttload of used P226 in .357 Sig configurations due to a lot of law enforcement turnovers. Simple decision and I never got excited about the .357Sig. I can get my .40 reloads to equal and exceed the .357Sig performance. Again simple.
