I have an old Colt AR-15 that works just fine but the barrel is 20" overall. I am looking for a 16" 5.56 upper for it I would prefer a piston gun but am really just looking for input on who has good uppers that aren't super expensive. I only have the one true AR-15 so I am fairly familiar but haven't ever really shopped around so I am not sure who is just over priced crap.