How do you change the metal outer barrel extension to a M15A4 Tactical Carbine Sportline airsoft gun?

Question

this is the website for the gun and it includes an outer black barrel extension, but don't know how to put it on

http://www.airsoftgi.com/product_info.php?cPath=139_24_204&products_id=3733

Answer 1

Just unscrew it.  It should have reverse threads on it though.  I'm not positive about that, but if you have been trying to unscrew it that might be the problem.