What Lou said.
If your bullets in pure lead actually drop at .580 (and just because the mold says it does doesn't mean it will), then you might get away shooting them in the original Springfields unsized.
I typically move up in sizers in .001" increments until the bullet doesn't fit, then back down one sizer. But since your bullet is (supposedly) .580 you can't go up any bigger than that. (Well, you can, with swaging, but I won't go into that).
Like Lou said, I typically go 40 to 60 grains in 5 grain increments, 5 shots in each group size.
Most of my muskets shoot 45-50 grains 3F, though I don't use full-size minie balls very much. I've bot a Pedersoli P58 (1:48 twist) that so far only likes a big heavy bullet with 60 grains 2F powder. I don't shoot it much because I have other guns that shoot less lead and powder and so are cheaper to shoot.
Steve
Steve Sheldon
Commander
4th Louisiana Delta Rifles
NRA Certified Muzzleloading Instructor
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