Hmm
So I take it real steel stocks are usable. How about front ends and rails? I saw in a review that someone had to modify their real-steal font set to fit it on, which suggests that AEG RIS sets and hand guards or usable. Or that WA got their dimensions wrong.
I might check that Pro Arms 5 piece barrel set Hitman was talking about. I saw it on WGC (or a clone of it) and it calls the m16a2 barrel an m16a2 commando, which if I remember correctly is 16". Never heard of an 18" barrel though.