S&W M&P full size 357 Sig Barrel in a Compact 40

[additionalmc]

I have an M&P40C, and recently aqcuired a 357 sig barrel, but it is for a full size, so it sticks out an inch or so.
Anybody have experience with a set up like this?
Is there anything I should be concerned with, especially the recoil spring?

 

[KMM696]

You should check if the diameter of the long barrel where it's contacting the slide is the same diameter as the end of the barrel. I can't remember offhand whether the M&P barrel muzzle is a larger diameter than the rest of the barrel. If the fit there is loose I would expect accuracy issues, and the slight possibility of function issues. I wouldn't expect the recoil spring to be an issue, going between 40 and 357.

There are aftermarket barrel companies that sell barrels set up like this, so the basic concept isn't in question. The question is how did the factory contour barrels.

 

[KMM696]

I wouldn't expect any real difference there,since 357 is based on the 40 S&W. 357 does have a ~10k psi higher pressure limit, but the bullet is usually lighter than the 40 so I don't think the recoil spring needs beefing up. If I were replacing the recoil spring anyway, It'd be the next weight up from stock, but I wouldn't say it needs it before firing.