What Jim states is good. Sometime back had one of Smith guys tell me even up to .010 ok as long as it was even all way around. Going to loose some velocity and might spit a little. .004 is usually what you want for competition gun. Too close and u will get build(lead) up and cyl might start binding on you. .005-.006 on an average desirable. We have machine rested some revolvers with up to .008 with no "real" loss of accuracy. Depends on gun and other factors including ammo that interact with each other.