I installed the low pressure springs frank suggested, seemed to dampen the sound a bit but not much. I thought the sound might be coming through the CO2 tank, so I had to change the trigger frame in order to change the ASA, and still had the clanging vibration. After a few minutes, I rested my chin on the hopper lid while the trigger in frustration, the noise was gone.
A few more minutes experimentation touching the hopper (GXG 50 round) with various body parts, I thought the hopper might not be seating properly, changed hoppers (JT 200 round) but I couldn't tighten the clamping feedneck enough. I had an epiphany, I switched back to the stock feedneck (the Outkast is blue and I had a 'close enough' blue feedneck lying around) and... NO CLANG! I tried another clamping feedneck and NO CLANG! Switched back to the blue feed neck and the clang was back.
PROBLEM SOLVED: improperly balance springs caused the vibration and a crappy clamping feedneck allowed it to ring like a bell. Thanks for the suggestions guys.
Last edited by cox_sp; 05-25-2013 at 08:16 AM.