Originally Posted by
Mr Wolverine
Piston diameters are different, we also use a nylon bushing where the steel gas piston enters the Aluminium upper. With out a NDS to compair I can not give you a definite answer at this time, it is possible it could be made to work. If RWA followed the original upper faithfully (which I believe they did) then there are also differances in the bolt carrier and other measurements. I think it fair to say that if people start rebuilding our rifles they run the risk of voiding our warranty.