Anybody know what they're made of ? I need to cast some balls for a ball mill , and have a choice of pure lead or tire weight material . I seesellers on ebay that have 10% antimony/90 lead for this use , others have pure lead . Still others have ceramic balls , but I'm not sure those have enough weight for a small ball mill . The one thing all have in common is that they're around a half inch diameter . I figger the .490 ball mold for my muzzleloader will work just fine .