Back in the 80s and early 90s, you could still order a cannon from Dixie Gun Works. A friend was in a Civil War re-enactment group and had a Dixie Gun Works cannon they used at all the events. I often dreamed of getting one as the ultimate ridiculous range toy.
Back then, you could order it with a custom bore, so he ordered his with the diameter of a common Campbell's soup can. He would save empty cans, then cast concrete in them to make projectiles.
It always tickled my redneck bone when I would get to go out with his re-enactment crew and they fired it on a live range.