Around Vicksburg 12 pounder and some six pounder case was the most common spherical shell. Some of you might be interested in how case shot was made. It usually had the borman fuse, lead balls being poured into the cavity. The shell was then filled with tar which served as a matrix which held the balls in place. A drill was inserted into the fuse hole and then bored out the tar and lead through the middle. Then the bursting charge was poured into the cavity of the shell and then the boreman fuse was screwed in. This is the typical way a 12 pound case shot was made.
Strangely at Champion Hill several case shells have been found that didn’t contain the regular round case shot but instead had a oblong/bullet shaped projectiles that contained powder. I assume these were firing at batteries in hopes of exploding the limbers. Mistakenly these mini projectiles were thought to be incendiary bullets but they are not. They are incendiary from case shot