RRA uses wilson blanks....their barrels HAVE RRA markings.... someplace. All of mine are marked about an inch in from to the chamber on the top of the barrel. The Free float tubes are not marked RRA, as most of theirs equipped on complete uppers are either houge or surefire (unless its the operator series, which it will be obvious that it is a RRA forearm by it's design).
The BCG and other small parts will not be marked on RRA on the parts as most (if not all) small and internal parts for most AR15 "Manufacturers" are manufactured in the billions by four or five major places and purchased by different vendors. You RRA may very well have the same manufacture FA assembly as a Delton, BCM, double star or colt.