I liked my BIL's Marlin Camp 9mm. He is reloading subsonic 147 bullets and with a 16" barrel it is quiet. Like my brother's AR9 pistol with a Gemtech can.

So, on a whim and no research, I purchased this PSA Glock mag 9mm stripped lower.

I know I want a Matrix side charging upper.
Eventually I would like a Law Tactical side folding adapter , but I'm not sure how that woud with with a 9mm build.

Everything else I'm open to suggestions. What else should I be looking at and considering? Thanks,

SS

Recently saw one on thread here with barrel removal option and LAW folder.
If you had a bottom feed Colt style block adapter you could make it 9mm 22lr interchangeable.

Hey I was wanting to do pretty much the same build. I noticed PSA claims their lowers have to be used with their hybrid upper and bolt to work properly. If that's the case then I'd imagine the matrix might have some issues sitting on the PSA lower. Let me know how it works for you

From what I understand that's a CYA thing on their part and as long as you use a Glock cut and ramped BCG any upper will work. 

Correct. Just need the proper bolt just like for any other Glock build

I went with the Spinta bolt, it can use spare parts from the CMMG MK9 bolts ( extractor, firing pin, etc)