I doubt it, firing every other turn it is still going to take a while to bring one down. Most stone walls will be saving on a 3 against the cannon, so only half the shots will get through. At the end of the game you might have shot through one wall, maybe. The best use I have found for artillery is shooting the wall so I can achieve quarter hits against the tree spirits and feral elves lurking on top of them....

You're probably right.

Where do you get the quarter hits rule from? I don't see that anywhere in the seige rules? Is it a house rule?

Probably. We figure the units on the wall are "engaged" with the wall and suffer half hits as if you shot into the melee. Since all units on walls are skirmished the half hits turns to quarter hits. If never made any sense shooting at the wall to try and break it down since it would take too long, and shooting at the models on the wall is very difficult (since they get that free heavy cover) and even if you hit them they only suffer half hits as they are skirmished. Really it was the only way to make artillery useful.

I can see how that would make sense ... but I don't think the rules support that as written. In the one game I played, a single light cannon almost knocked a castle gate section down. I suspect playing with artillary using reduced costs due to single shot will be enough to make them competitive.

I personally think that the opposite rule might be more appropriate ... any area effect missile hits that targets the defenders on the wall and hits also counts as hitting the wall section. After all, a rock fired from a catapult is going to pass right through an infantrymen on the wall and continue to smash into the wall. However, a cannon shot fired at the base of a wall probably wouldn't affect the defenders on top of it.

It works both ways. A hit on the defenders does count as half hits against the wall as well. A gate hit is different, the defenders are not riding the gate, they are riding the wall around the gate, I wouldn't expect men on the wall to take damage from a gate hit. IN thanes example the gate is an extra portion of the wall it is set into, so even if the gate comes off its hinges the wall around it is just fine.

As for breaching a wall....trying to breach it from the bottom is extremely difficult. The stones on the bottom are not only larger they have the pressure of the stones above them, they are much more difficult to move. A breach in the wall was much more likely to occur well above the base where the stone was thinner and the pressure less, and well above the base means hits are likely to shower the defenders with debris from the wall and the stone. The only times that I know of walls being breached at the base involved two things: smaller walls (such as those at Drogheda when Cromwell breached them) and rifled cannon who transferred energy in a much more efficient way. Older cannon, mortar, ballista, catapults, due to their arc are more likely to hit the top of the structure rather than the base anyway, especially those with the greatest arc such as trubechet.

That makes sense .... I'll try it out in one of my future games.

What are your thoughts on what should happen if a castle section loses all wounds? Should the whole section be removed and replaced with an area of difficult, rocky ground ... presumably damaging those on top of it and those perhaps climbing up / assaulting at the time? Perhaps it should represent a breach and simply remove the defender benefits of climbing and defending from a parrapet?

Considering the amoung of effort required to bring a large castle section to zerio wounds, I'd think it would result in something more castastrophic and damaging to the defenders.

Another option could be that once the section is reduced to half wounds, it stops giving the defensive parapet benefit ... once to zero wounds, it collapses entirely?

For seige games, it might be useful to keep the canon at strength 4. Castle walls can be very hard to knock down otherwise.