I am considering a pistol cartridge AR type.
The CMMG, 9mm, DRB2 has my interest.
Does anyone have any experience with this?

I've built a PCC with CMMG Guard parts (lower, upper, barrel, BCG). It's very soft shooting. With soft 9mm loads it's like shooting a .22LR. I made Grand Master in Steel Challenge with mine this summer.

I had a lot of problems with it initially (failure to eject that would induce a double feed). CMMG was pretty helpful and after I tried a few fixes on my own they sent me a replacement ejector spring. They said the "upgraded" that part, I suspect they just had a bad batch. Either way, I'm at 500 trouble free rounds now with both 124 and 147 grain factory loads.

Mine has an 8" barrel and pinned 8.5" aluminum shroud to keep down on weight. BCM rail and Geissele trigger. The recoil seems the smoothest with no carrier weights, a standard carbine buffer, and a Sprinco red spring.

Thank you for the information. I am seriously considering one of these. I have yet to see one in person.