"There were probably more round ball explosive shells used than all the rifled shells combined."
I'm not sure I'd take that bet.
By the end of the war the Parrot, Rodman, and U.S. Ordnance rifles were in heavy use, and pretty much all they used were shells.
In addition, for Naval use, the shell guns had largely replaced the roundball guns by the middle of the war for new construction.
"The gift which I am sending you is called a dog, and is in fact the most precious and valuable possession of mankind" -Theodorus Gaza
Baby Jesus cries when the fat redneck doesn't have military-grade firepower.