Have seen a couple of S&W barrels that benefited from a recrown but frankly have no urge to replace the barrels on my Pros.
Like texas48 said, KKM makes excellent aftermarket barrels, but why do you think you need it on your M&P?
With 1" ammo and a 2" gun in the hands of a 5" shooter, you still get a 5" group.

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