I did the RF20 mod on Den of Foam, The Black Knights' nerf site, but when I tried to fire the gun when I put it back together, it just made this horrible hissing noise. The barrels didn't rotate, and the piston didn't move.
HELP!! PLEASE!!
Did you put the rubber black thing over where the air comes out with the two holes in it back in the right way? It has to be put in with the holes in it vertical, they CAN NOT BE HORIZONTAL. I did that on mine and it took me a day to figure out what was wrong with it.