Non veni pacem mittere, sed gladium.
Looks more like a round from a Hotchkiss 1.65-inch (42 mm) light mountain gun. It replaced the 12 pound mountain howitzer.
http://www.cannonsuperstore.com/hotchkiss165.htmlOne for sale...Steve
That skull was hit by a single one inch round ball from a civil war canister round. It was a mostly "spent" round that was "skipping" along the ground (something they'd do for more than a mile) and hit him from behind moving at an "up" angle. A 12 pounder was a 3 inch gun that would have taken his skull and upper body apart at a mile or more.---Ray
AKA grapeshot. Lived 10mi from Gettysburg...those steel balls were everwhere.
Doubt he felt anything. One second he was, the next he was not.