Well... unless something is really out of whack, I don't think the receiver or hand guard and for that matter the bolt carrier play that big a roll in this. Let me try to explain.
The barrel extension screwed into the barrel and the bolt lugs locking into the extension hold all the pressure and are the only sold lockup in the system. The bolt relies on gas rings to keep it lined up in the carrier, the upper receiver has enough slop in it to allow the carrier to run back and forth. Even a tight "bedded" barrel/receiver only keeps your sight plane straight.
Think of it as a bolt gun, you square the receiver to the barrel. In an AR this is the barrel extension into the barrel. The aluminum receiver will conform to the barrel extension, unless it's way off, it ain't gonna matter how square the receiver is.
Next you have a bolt guns bolt lugs lapped to get even support to line the case up. With an AR, the lugs lock into the extension to do the same thing. The pressure on the gas rings, the slop of the carrier inside the aluminum receiver play little to nothing on the way the bolt locks into the extension unless something is way out of whack.
So as long as the bolt settles squarely into the extension supporting the case squarely into the chamber, it's gonna shoot. At least that's my understanding of the system.
Please don't think I said it doesn't matter if anything else is square or not or read anything into this but if the bolt doesn't lock into the extension squarely and the chamber square to the extension, it'll never be right. I'm sure I explained it clear as mud.
