Keith,

No I didn't contradict myself, and that should be apparent if you read what I actually wrote. I was pointing out the difference in CSA and USA 6 pounder explosive rounds. If you go back and read what I wrote I said "U.S. 6 pounder gun" and then contrasted with the CSA 6 pounder polygonal cavity shell. Were some 6 pounder polygonal cavity shells actually filled with shrapnel? Quite possibly, but I can only go by what authors, photos, etc. have published. In those they are referred to as "shell." Shell does not contain shrapnel. Shell that contains shrapnel is known as "case" or for smoothbores "spherical case." (And in After Action Reports the term "spherical case" is sometimes substituted for "case" or "shrapnel" when referring to rifled rounds.)

At any rate your intial "corrections" were mostly in error:
1. "Smoothbores shot 3 kinds of ammo, solid shot, case shot, and cannister. Period." Patently false.
2. "Shell is a cylindrical round with a sabot of many variations." Again, wrong.
3. "Only rifled guns fired shell." Wrong.
4. "Shell for a smoothbore was a hollow roundball filled with a charge and shrapnel." Wrong.
5. "The same for case shot. The difference being the cavity shape."

No, the difference is not the shape of the cavity per se but the presence of balls or other shrapnel in case. The burst charge was smaller in case, and the wall thickness was also thinner for case.