.0750 or number 31 drill bit I think? I left out one zero. Although some refer to a .750 gas block = barrel size in low or medium. I quess I should have mad that more clear. Have heard of guys going to .1060 on some 300blks. But i fell that might be to far??? Whats your opinoin own adjustable gas block Vs Lighter bolt and buffer tube = for the intent of shooting ONLY subsonic ammo and have it cycle?
