The Mexicans were short on lead and often used copper balls. Not easy to cast at home and expensive. However effective. Copper is lighter then lead so the ball couldn't keep velocity as well but in smooth bore rage was just as deadly. If you patch a ball in pure lead in a rifle you leave an imprint of the patch on the ball. It grabs the ball well and holds the rifling. A hard ball will resist that. I don’t reckon a smoothie cares.