The Hornady 000 is .350, not .360" as nominal for triple ought buck.
Yes, it and their other buckshot down to at least 00 buck are hardened. That stuff was .320" and hard loading in my .32, too hard. .320" pure lead balls I cast in my Lee DC mould were easy loading. Yes, the Lee mould cast oversize, but perfectly round except across the tangential spruce to the bottom of the ball.
Mere hand pressure against the patch ball would form the .320" ball and .021 to .0235" patch into the muzzle. Then, a choked up rod would get the ball and patch.moving down the bore. Small balls are easier to load tightly, than larger balls.