Alright guys, I've been a long time lurker here in the semi forum but I havnt posted. A guy I work with heard I was in the market for an AR and said he has one for sale. I know next to nothing about the platform as I am a bolt guy, so I am turning to you guys for help. He said its a cmmg upper on a roggio machined roggio (sp?) lower gas piston gun with an RRA barrel. I forget the manufacturer of the trigger, but I looked those up to be reputable. My main concern is the upper/lower setup, any input?