The potato was sent flying through the air in two parts, and then disintegrated at the apex of its flight. A massive fireball exploded out of the potato end of the cannon, with two smoke colors and a rapid popping noise. The black powder end of the cannon set the grass around it aflame and blasted a small hole in the concrete behind it.
So today we're planning to put in 30,000 matchheads and three fireworks-worth of black powder and explode it soon. I'll see if I can get a video out.