I recall all the old literature about following at biting distances than 000 or SG buck shot ie: .36 cal balls. Brass shells were used - these writings were taking place in the 50's I assume. Nowadays the 000 shot sold for reloading by Hornady is .35 cal, which probably makes no difference. 00 and SSG is .32 cal., again, at 5 feet, probably makes no difference. I do know at 5 feet, they'll penetrate a black bear's skull quite well, but not at 20 yards.