I'm building a cqb upper receiver for my hpa rifle. It you already have one built, feel free to send pics and we can discuss. Otherwise I'll need the following: Metal m4 upper receiver (AEG) 4 inch metal free float rail 7 inch metal outer barrel Afg NC star red/green/blue rgb 35mm tube reflex sight Echo 1 combat flip up ironsights (or any other cool ironsights)