KWA M4/M16:
http://www.kwausa.com/forums/index.php?showtopic=1711
What does Part #2 do? Mine does not have that part, instead being wrapped in teflon tape.
I'm assuming the last gunsmith to have it apart (a reputable one on this forum) did this? When I got it back from him, it worked fine...for 2 days. Now the old problem is back--velocity has dropped to about 250 fps (from 380).