I was not aware RR had a "large" front pin as with the old Colts but bushmaster makes an adapter none the less. You may have issue with the notoriously tight fit between the upper and lower that many RR's have. I could not use one of my 416 uppers on a Noveske for this reason.Alright guys--- I need your assistance on a Z-Apocolypse build!!! :wink:
I have a pre-1994 Rock River Arms lower (presume small hole upper- front pivot pin lug/rear takedown lug).
My question is this--- will an MR556 complete upper attach perfectly to the RRA lower? :biggrin: