the one i have now(broken) i made a long time ago and there is only about 2 threads on it so its pretty hard to check threads. also its on a spyder style gun that i modded so its not a standard part. but thanks a bunch for the link it got me the answer 3/8-24 which i believe will fit.
fatty full body spyder with benchmark frame, the new anti chop bolt and all billet parts by brmachine.
BR Machine rebel-250psi opperation pressure, antichop
Brass Eagle low pressure avenger with esp frame...