Musket balls

For our hoplological friends: what effects, if any, would be observed by making musket balls out of cast iron? I know cannon balls were made this way, but that musket balls were almost always lead for convenience, so I'd assume some increase in cost (?how much), but would there be other effects?

I'm also assuming that, practically, this would be a silly thing to do ... unless, for example, you happened to have a fae problem...

Musket balls