Any model struck by a cannonball takes a Strength 10 hit. Roll to wound as normal. No armour saving throw is permitted for wounds caused by cannons. If a cannonball hits you, no amount of armour is going to do you any good. Ward saves can be taken as normal. Unsaved wounds cause not 1 wound but D3 or D6 wounds, depending on the size of the cannon. As most models have only 1 Wound anyway, it will not be necessary to roll this extra dice, but it is important when it comes to rolling for Heroes, big monsters and other models that can take several wounds.