Hal, what is the rate of twist? I'm thinking that a rifle of that vintage might have been meant for round ball use, so if the twist is slower than about 1:48 I'd try a patched RB first. A .58 RB will blow right through a whitetail at 50m, as you know - and a 1:72 twist won't stabilize a conical too well.

Let us know how you do!

I love the smell of sulfur in the morning - it smells like . . . well, like rotten eggs actually. :-)