Last year I picked up a Keltec CP33 and when I was watching some videos I stumbled onto some videos about using it as a "cheek pistol". And it's been awesome. It's one of the funnest guns I own now. Now I'm wanting to take the concept to the AR platform and I'm trying to figure out what the best option would be...

I'm debating about whether to get something like an FM15 11" or getting like a regular 7.5" AR upper and finding the shortest buffer tube I can? Has anyone built one out or have other recommendations?

5.56?  Have you ever shot a 5.56 that was that short?

No, but I know it'll be loud and have a nice fireball

I'm thinking about adding a suppressor to it, but we'll see how I feel after I shoot it

I have an Olympic OA93 which is a 7.5" barrel.

I don't want that motherfucker anywhere near my face when I shoot it. In fact I haven't shot it in many years purely due to the fact it is obnoxious.

Makes a 2.5" .357 seem tame

You aren't going to want your face, nor ears, anywhere near that receiver.

If your serious, I’d recommend a 8” BRT barrel and get a Ti can with a recessed direct thread mount. It isn’t going to be quiet, but it won’t detach your retinas.

The pistol I posted previously in another thread has a 7.5 bbl with a Noveske KX3 on the muzzle.

With a KX3 I don’t really notice much of a difference from that vs. any of my other rifle length uppers. It pushes all the blast and a lot of the sound forward and works very well.