It's okay if you dont. It was way back when I had my very first Oldhammer battle with my boy Bloo, Battle Report.
Well I give you Battle Masters...Fire the Mighty Cannon
* taken from a review on board game geek
"THE MIGHTY CANNON has its own special rules, and like the archers and crossbowmen, can only move or attack. If it attacks a unit right in front of it then a tile is flipped and the enemy unit is destroyed automatically. But the cannon may be as well if a Misfire was drawn.
Firing at range though employs the cannon tiles in a very fun way. The target must be within 8 hexes of the cannon and then a line of cannonball tiles are laid out towards the target in the shortest number of spaces possible, but in a path determined by the attacker. The Target marker is placed on the unit you are firing at. The other 9 cards are shuffled and laid out one at a time.
If the very first cannonball tile drawn is the explosion, or you are firing point blank. Then you destroy any unit in the tile where it exploded and then must shuffle the remaining tiles and see if the cannon misfired. A result of a bounce inflicts a Skull damage on the cannon. And a result of an explosion destroys the cannon!"
So with that in mind and using the new Donnybrook rules If the cannon bounces it will cause one wound, and if it hits it's target it will cause a roll of a d8 that roll will then determine how many d8's to roll for damage. Hit on a 6+. A fun rule but not over powering I think.
Here a shot of him in action!