Splitting the ball off a real double bit axe sunk into a chunk is what we used to do at Chilliwack Buffalo shoot. It was called the "Buffalo Shoot" as the prizes were various cuts of buffalo meat.
When I was dating my current wife (just celebrated our 40th anniversary) I won 40 pounds of meat at one of them. 10# for a first, 6# second IIRC and 2 or 3# for a third. I was shooting a Bauska Barrel, a .50 with 38" twist .008" rifling and 80gr. 2F with .022" 'brushed denim patch and a .495" pure lead ball. WOW - all coming back to me. I used the same 80gr. charge with 350 to 450gr. slugs for bench shooting and turkey shoots at the Burnaby range.
Taylor was shooting his .62 Hawken, a lovely rifle, with 10 lines to the inch fiddle-back Eastern Maple. The hole the screw-head (welded to the axe head-not a Double Bit axe) got loose in the chunk and they had Taylor bore them a new hole with his rifle for the 5/8" bolt! I think he was using about 180gr. 2F then. Good shooting load. He also won the 250yard buffalo match on a steel gong target. 42 years ago. Don't ask me what I had for lunch yesterday, though.
Splitting a ball to break 2 clay birds, is easier than splitting cards as any part of the ball will split off and can break the other bird, however, if not almost perfectly centered on the card, the ball's edge will bend the card and only cut a snip, or part way through. Only completely cut cards count.