CMMG RESOLUTE 9MM Mk4 the model with conversion mags. Not the COLT or Glock mags.
The radical delayed blowback makes it one of the best AR 9mm out there. Hard the beat in a PCC unless you spend a ton.
CMMG is a decent company, and their radial delayed blowback is an excellent design. For an AR patterend pistol carbine, I wouldn't go with anything else. Quieter when suppressed (due to delayed blowback), and far cleaner operation too. But I'd have to have mine in 10mm!