Certain dimensions may be similar, or even exactly the same.

However, PRESSURE, which is a major factor in function, wear and safety, is different enough that S&W no longer offers a specific .357 SIG product in the M&P line and recommends not adapting a lower pressure-designed gun to run a higher pressure cartridge--or do it at your own risk.

IMO, the risks and liabilities associated with such a caliber change just aren't worth it. Fans of the .357 Sig caliber will disagree, believing it has certain positive characteristics. I have been there and done that with another manufacturer's pistol with their own manufactured barrel, and it busted up the weapon. I gained so little in performance and so much in cost and aggravation that I won't do it again.