Here is picture of current 58cal slug options that
you can get molds for from Lyman,
Just make sure they are .574" to .577" diameter.

A barrel of 585HE cases..Ed

Made by Bertram and I tested them to max loads and cases hardly expanded,
650gr over 3000 fps. The same draws used by him to make high pressure
Cheytac cases, and to finish mine just uses belted header and cases left
straight and trimmed longer.He makes tens of thousands Cheytac steady all
the time now and can make ours steady also when needed.....Ed