I have no experience with those firearms. From what I'm reading, wheel weights were in the range of ~10-1 antimony. "The Book" (Wolfe https://the4570book.com) specifically says to run away from anything with antimony in it for trapdoors, and to stick with the 20-1 tin, or less tin, for best accuracy. I have high hopes for these, but I'll be happy so long as I don't have to aim at the floor to get on paper like the others
Been thinking about casting for myself over the last year...but the highly prized saeco 1881 mould has not presented itself.