A couple of years ago on the Spelljammer Mailing List I brought up the question of whether or not the cannonballs from a bombard exploded or not. Well, it turns out that some cannonballs did explode, and a friend of mine in a history class managed to get a few tidbits on them from his professor. So I made up some rules to reflect them.
It is possible to create bombard shot that is filled with smokepowder that can be lit and then fired, exploding on impact. This increases the damage done, and can ignite the target ship on fire. The drawbacks are prices and reliability. Any bombard can use exploding shot.
Lighting the Fuse: An exploding cannonball has a fuse that sticks out, and this must be lit for the cannonball to explode. There are two ways to do this. The first is to light it by hand before dropping it down. This is risky, as it will be ignite the smokepowder firing charge and fire the bombard. Only very experienced crews fire this way. It adds a round to the rate of fire (i.e. 1/3 becomes 1/4), but guarantees that the fuse will be lit.
The second method is to roll the ball so that the fuse is facing the firing charge, so that it is lit when the bombard is fired. The chance of it lighting depends on the rating of the crewman rolling it.
Rating Chance Complete Novice 3 in 10 Green 5 in 10 Average 6 in 10 Experienced 7 in 10
If the roll to hit with a exploding bombard shot is a 1, the ball will explode in the cannon. If the leader of the firing team can make a successful skill check against the appropriate Large Weapon skill, the explosion is contained in the bombard, and must be scraped out before it can be used again (requiring at least an hour). If the roll is failed, or no one has the skill, the explosion rips the bombard apart, doing 3d8 points of damage to all within ten feet (save for half), and 2d4 points of damage to the ship, 1d4-1 of which is considered fire damage.
Damage: An exploding cannonball that strikes a ship is not guaranteed to go off; the fuse may go out. In these cases the shot shatters and spreads its smokepowder around the impact area, which may ignite later. The chances of the shot going off is 8 in 10. All other stats are as for regular bombard shot.
An exploding cannonball does 2d6 points of damage. Half of this is fire damage, as per the rules in the Concordance of Arcane Space, pg. 61. If the cannonball does not explode it still does 1d4 points. Anyone within ten feet of this takes 4d10 damage as well, and anyone with twenty feet takes 2d10, unless they have some sort of protection. A save for half damage is allowed.
If the shot misses, it may still explode. If not, it may be recoverable, but will need a new fuse.
Cost: An exploding cannonball has ten charges of smokepowder in it and requires a very skilled person to create. They are hard to find, and cost 300 gold pieces each. Replacing a fuse costs 5 gold.
