Re-crown and loosen up the barrel clamp. We used to have the same problems with the M73 machine gun on the M60 Tanks. The tighter we screwed down the barrel jacket the less accurate the gun was. When we loosened it up the better it shot. You gotta let the barrel do its thing. It's gonna vibrate and the more you snug it down the less its able to vibrate and do its thing. The more you tie it up the worse its gonna shoot. JMOOMV.
