Tonto,
I don't know if it would fit into a RB #1 action. I'm quite sure that it would not fit into any of the others. But there aren't a lot of .58 centerfire cartridges out there (the .577 BPE being one of the few that is in the ballpark).

I would also wonder if the twist is right for anything but roundballs. Sorta depends on the details of what you actually have and where you want to go. Who made the barrels, what's the twist, and how wide and long are they?

Brent

Tonto: Seems I have heard of shotguns as large as 16 gauge being built on rolling block actions. Some of the fellows shooting .577 Sniders are using Magtech/CBC 24-gauge brass shotshells to make their cases. Be advised though that a proper .577 Snider bullet is actually .590. Sniders with the original 1:72 twist are on the edge of stabilizing most conicals, especially the heavier ones, but the Sniders in 1:48 are about perfect.

I was looking at some of my parts last night I have 2 very heavy octagon 58 calb barrels. was thinking maybe they could be used for a 58 calb blackpowder round? what were some old ones? Would a rolling block action handle any of them?
Dean