Convert M&P 9mm to 40 or 357 Sig?

[razorback2003]

Can you convert a smith and wesson M&P 5 inch Pro 9mm to 40 or 357 Sig by just swapping the barrel and magazine? I have read that the M&P was built on a 40 caliber frame.

 

[wally]

Nope, the slide cut where the cartridge fits under the extractor is too narrow. You can convert the .40 to 9mm because the smaller 9mm cartridge will fit -- its a little sloppy which leads to erratic ejection and the occasional stovepipe, but its a viable alternative for shooting cheaper practice ammo.

I've got a 9mm barrel (from S&W via Midway) for my M&P 40C and a threaded 9mm Storm Lake 9mm conversion for my M&P 40. Both work well with the above caveats.

 

[exdxgxe4life]

It's my understanding that you need a 40 to shoot a 9. Pretty lame I know.