I just bought a factory M&P .357 barrel for my M&P40 and was wondering if it is the right thing to do. I could see going from a .357 to a .40 (.357 @40,000psi and .40 @35,000psi) but will this cause added wear on the frame, or is the M&P built the same between the two calibers - with the exception of the barrel? Also wondering if this would void the warranty. I usually never change things on a gun, especially a perfect gun like my 40, but I couldn't resist having two calibers in the same gun for $100.00. Thanks for all thoughts and info.
The part numbers for both the 40 and 357 recoil spring assy are the same. The frame is the same for both the 40 and the 357. The only difference between the slides are the caliber stamp on the M&P logo. The mags are stamped for both the 40 and 357.
Change the barrel, shoot it, and don't worry about it. I have been for about 150 rounds now. Slide says 40 barrel hood says 357. Shoots just a bit low with 125 grain Gold Dots out to 25meters. Other than that all is well.
