Most pistol calibre AR pattern barrels are direct blowback and do not have gas ports or an interface for an AR pattern bolt as used by Troy.The PAR or SAR sounds like all it would need is for the face of the bolt to be altered, and the gas port of an off the shelf AR 9mm barrel plugged.
Add an off the shelf STANAG to 9mm mag well adapter and some glock magazines..... am I missing anything?
I'd be pretty happy with a single shot break action 9mm option for casual plinking.