Caliber conversion
 

Is it possible to convert an S&W M&P compact from 9mm to .40 S&W with just a barrel and mag swap?

Thanks

In short no it is not but in the other case it is from 40 cal to 9mm.

You can buy a 40 and convert either to a 9mm or a 357SIG which is what I have done with my S&W M&P40C using a Storm Lake 357SIG barrel which I just tested this afternoon at the range and was very impressed. I also have a post about why you should buy a compact M&P and most of all a M&P40C for this versatility!

Thanks, I thought the barrels were the same diameter. Appreciate the info.

Barrels are the same but the breech face is different. That's why you can go down but not up.

Gotcha. Thanks. I have downconverted a couple of Glocksj and a Browning Hi Power, and that's the way you have to do it. Appreciate the help.

As with most weapons especially the M&Ps you can buy a compact and use a full sized magazine but not the other way around.

Had I known what I just said above a few years ago I would have said buy a M&P compact and be happy with your purchase, but no I bought a full size 9 which I love a bunch but had I done it differently then yes that would have been my choice!