I once saw a book, published during the second world war, with descriptions large guns (canons) used my the U.S. army and other forces.
The two fascinating things about the book:
1) Wartime censors had cut rectangular pieces out of some pages of the civilian-distributed book to preserve military secrets.
2) Canons listed in the book were rated in terms of how many horses and men the projectile could penetrate.
If I recall correctly, Verne's "From Earth to the Moon" also makes reference to canons having an estimated rating in terms of horses and men, and even makes a joke about a lack of volunteers for actual testing.
I assume that the horses and men rating must have been based on actual tests on actual retired cavalry horses, but I also can't believe that such crude testing was still being done at the dawn of the first world war. There must have been a way to measure or calculate the force of a projectile and convert that abstract mass and momentum data into the traditional horses-and-men rating. I would like to know how this was done.
Google searches aren't showing me anything. Any suggestions?