Is it possible to convert a 40c to 9 millimeter by removing the barrel and magazine from a 9c and putting them in the 40 C? Is life that easy?

There's a lot of talk on here about it, so I would search for more detail. Most use the Storm Lake barrels, but from what I understand, yes, that's all there is to it.

I'm guessing you haven't done a simple Forum search on this? There are literally dozens of threads about it (almost a weekly thing). There's one discussing the 40/9 FS still on the 1st page of topics.
(Same theory, different model.)

Yes... If you want to go the cheap route, it can be done that way. The Lock-Up isn't as perfect as buying an aftermarket 9c conversion barrel specifically made to be used in a 40c, but Many have done it and have had no problems.

If I were to do it, I'd spend a few extra bucks and get a barrel designed for the job.

I use an OEM 9mm barrel and magazine successfully in my FS M&P 40. However neither are compact models. Perhaps someone with exactly that experience can tell you more?

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M&PC FS BG Shield+ 642 686+

Yep, life is that easy. I've done it and it works.
However, as Rob said, a better way to go about it is with a conversion barrel designed specifically for that purpose.
I have a KKM 40 to 9mm conversion barrel and it has been flawless.

I use the 9c barrel in my 40c quite often. I was lucky enough to grab an OEM one before they disappeared and it has been flawless. I use 9c magazines mostly or sometimes a fullsized 9 with the x-grip.

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MP9 40c MP22 15Spt 9Shld 15-22

All the M&P 40 models can swap out the same model 9mm barrel, and turn the gun into a 9mm. In many cases the 40 mag will feed the 9mm rounds fine. Should work good for use in practice, for less recoil/flip and cheaper ammo. The swap has been done by hundreds of members of this Forum. Works with 40 FS, Compact, and Shield.

The current issue is you can't find the 9mm barrels.

Bob

Nevermind, I found a FS conversion easily, forgot this was for compact.