CMMG makes a good 9mm upper, and they sell a stock PMAG 9mm adapter insert for a stock AR lower - no mag well insert required.

https://cmmg.com/adapter-magazine-9-ar-conversion-10-30rd-2-pack

You-Tube shows the conversion running, I haven't tried it - but I do have a CMMG pistol upper that runs great on a dedicated 9mm lower for Glock mags.

I like the radial blowback design, seems to be reliable so far, and an easy way to dump money at the range...

Last edited by AH64guy; 12/14/21.