Originally Posted By Suburban:
So. what is the compatibility situation with the 9mm Resolute uppers, other than CMMG dedicated lowers, and the CMMG/Endomag magazine guts?  My fantastic Hahn block for Colt mags doesn't work.  Recover Tactical specifically says their pistol mag adapters do not work with CMMG radial-delay uppers.

Originally Posted By amphibian:
TMK, other than what you already mentioned, they only offer parts to convert their blowback lower to run Colt mags.
For Colt mags to run in their blowback lower: https://cmmg.com/parts-kit-mk9-9mm-radial-delayed-blowback-colt-metalform-mags
For CPD mags to run in their blowback lower: https://cmmg.com/parts-kit-mk9-9mm-radial-delayed-blowback-asc-cpd-mags

Before they came out with those kits.  Several people including myself modified lowers / mag blocks to run un-modified Colt Mags.
I have this documented on my site here: https://c3junkie.com/?page_id=374
I'm using a Hahn block as well.

I have friends that have also did the Stern mag block to run Glock mags.
Several people have done other variants.  
Here is a thread using Scorpion mags: https://www.ar15.com/forums/AR-15/New-NFA-S-9-Lower-Scorpion-mags-Pics-and-build-in-progress-with-CMMG-RDB-UPDATE-8-25-IT-LIVES-/15-754694/

Originally Posted By Suburban:


So you modified the mag catch to hold the magazine lower?  But that also allows the magazine to "float" that amount in the magwell, and pressure on the bottom of the magazine will stop the bolt again?
I don't think I want to do that.

I can try lowering the mag catch of a 3D printed Hoffman Tactical lower by .060   .080"