Originally Posted by kullwarrior
Umm mac, if you don't know a WA, G&P, KA, AGM, CA, JG receiver is off dimension than the firearms one, if I recall correct it is shorter in lengh, thats why there's a misalingment of the grooves on external looks.
I don't understand what your are saying? Will a real carrier fit in any GBBR, will any of them accept real lower parts in the trigger-hammer chain, or will the hammer strike the firing pin of a real carrier? Will a real barrel fit any GBBR uppers?
I have an AR, so I have parts. I have no GBBR, so I can't say for certain. But from what I have heard, WE ran into some trouble with this in the US, and so did G&P. From a design standpoint, it would be orders of magnitude easier to do this with a GBBR than to modify an AEG, which was my point.