I got pure lead from a reloader supply nearby--it wasn't dirt cheap, but it wasn't terribly unreasonable. I do need to check out a plumbing supply shop as I get more into the casting. This was done with a friend's Lee pot and mould. All I brought was the lead. It was my first lead casting experience. Now a pot is on my Christmas list--along with some moulds... especially round ball moulds.
Anyway, as mentioned above, the Lee R.E.A.L. bullets must be cast from pure lead, same as round ball. I think the same would apply to conicals. At the velocities we get with black powder, there wouldn't be a reason to use an alloyed lead anyway. At least not without getting into unreasonable or unsafe loads for a TRADITIONAL muzzleloader. I think if there are any exceptions, they would be more applicable to the inline guys--especially that new Savage. Not for the traditionals. Correct me if I'm wrong, guys, of course.
Keith