I used to play around with a multible ball load, where I would take usually three fifty cal balls and drill a hole through them, and tie them together with heavy fishing line. I would tie them about 6 inches apart.
I shot these in a 12ga muzzleloading shotgun, using newspaper for wadding, top and bottom. And I also used it in a 54 cal double rifle. In the rifle I would load one barrel with a plain old 54 cal patched roundball. The other barrel I first pushed down a plastic roundball patch, ( I don't know if they even make these anymore, as they wern't much good for anything anyway), then loaded my three ball load, along with a little bore butter to keep everthing nice and slick, then I pushed another plastic patch down on top.
I never killed anything with it, as it's not legal in my state, but it made some pretty deadly looking, but sometimes sorta odd patterns on the targets.