One of my father's neighbors has both a cannon and a mortar. Both are blackpowder. I've been there when said neighbor has touched them off--both at the local rod & gun club's ranges, and down the street in the housing development they live in (it's a close-knit neighborhood, and they've taken steps to ensure that nothing gets damaged, and so far, nothing has). This guy's had these artillery pieces for about 20-25 years. The "projectiles" are cement-filled dog food cans. Kinda easy to find, too, once they've been shot.
