It's a sportline that i got when they first came to Canada back in 2008 or 2009 before i knew any better and before I was av'ed, the lower is tinted plastic and i am not sure what the upper is the thread is metal though. the slip ring that came with my rail fit perfectly onto the threading, i had to remove the entire delta ring and attach the slip ring where the delta ring was.
I figured out how the rail should sit on the gun in any case but i still can't put the rail on because of some blocks sticking out of the side of the bottom of the barrel assembly:
http://mach1airsoft.com/product/a3-f...er-barrel-set/(click on the pic to see what I mean) they were used for the standard delta ring.
if those weren't there the rail would fit perfectly and the top rail would even perfectly line up with the carry handle rail.
I don't like the idea of grinding anything down or chopping anything so i think i might just sell the Gun and get something that's more TM compatible.