In the late 1960s, a civil war ironclad was located in Mobile Bay. Divers brought up the cannon ammo, set it on the dock, and left it. Our EOD unit was sent down. The rounds were placed in revettments, a minature shaped charge placed on each one, and fired. A significant percentage of them had secondary detonations, indicating the powder was still good. That was after soaking in water for over 100 years. Like old men, old ordnance can still be dangerous.
The muzzleloaders used several different rounds, Most commonly shot, shell, and cannister. Cannister is God's own shotgun- lead balls in a thin container. Shot is a solid ball. Shell is a hollow munition, with a bursting charge. Some were quite large- friend found a 13" mortar shell on his property near Petersburg VA (left there by the damnyankees
) That is an explosive round the size of a basketball.
The White House of the Confederacy had used a 4 inch Parrot gun shell (rifled cannon) as a doorstop for years- until someone noted the black dust on the floor behind it. Yep- live shell.