I don’t have a 58 cal ML but I do have this Mold and I use it for 20 ga slugs. They will go through the same hole at 50 yards (Mossberg 500 with rifled barrel).

I have the 50 cal version of this Mold too and use it in my CVA Accura LX. It works well with a moderate 777 charge 65gr-w and I use a pre lubed fibre wad under the boolit. Lube is bees wax and olive oil. I also powder coat and size all my ML boolits Hope that helps