Glock interchanging calibres for a model 22, 23, & 27
It is true that you can purchess a new barrel and get the choice of firing both the 40 S&W and 357 Sig in the same pistol. The cartridge base is the same and the recoil pulse is close enough the the standard spring works fine. The mags are interchangable as most of the 357 Sig dimentions are again the same as the 40. I have fired both, it seemed that the 357 cycled faster with less muzzle flip. That was probibly due to the fact that I was shooting a lighter weight bullet in the 357 sig which would be operating at a higher velocity. I have been through the Glock armorer course and as a non gunsmith the pistol is very well thought out. Having said that I still prefer the trigger on my Custom 1911 Springfield 45 to the less crisp springy trigger in my 40 cal Glock 35.