Help with canons/ironblaster

So I'm a noob using canons and the ironblaster, I've only used it for 2 games and haven't used it to shoot anything besides monsters so far so I'm wondering how it works a little bit. Here is my question:

- I shoot a unit of 1 wound models.
- Canon hit
- Roll to wound
- It's a wound

Now, I roll the d6 for the multiple wounds rule if it's possible for the enemy to save one, but do excess wounds carry over to the rest of the unit or do I only inflict one wound and proceed with the next rank? I guess the multiple wound rule just isn't clear for me. Thanks in advance!

Well let's say you shoot at a unit with 5 ranks, you manage to hit a  model in each rank, basically you would just throw 5 dice to wound, any 1's wouldn't wound.
you don't do multiple wounds against the unit, if all the models are single wound infantry for instance, then you have allready hit every single one of them, and even if you don't wound the first one, they won't stop the cannon ball, they've all been hit.

But let's say the first guy hit was a character, normal infantry, you would roll to wound then roll a d6 for multiple wounds against that guy, still the same thing happens to the rest of the unit, they are all hit, even if you don't wound or kill the multiple wound character up front.

The above is pretty much bang on the money, don't forget though that in the event the first model hit is a multiple wound model such as a hero or lord they are eligible for their Look out Sir. In which case it's just roll to wound the models that are hit and incldue an extra wound for the LoS roll instead of the character.

The multi-wound rule is always applied regardless but seeing as single wound models have 1 wound and the lowest result is 1 anyway you don't need to roll. The excess wounds are lost and don't spill over onto the rest of the unit as they weren't hit by the cannonball. Remember in the case of War Machine type weapons (in fact pretty much everything in the game), you can't wound something if you've not hit it first.

A handy little trick for the cannon though is to aim roughly 8 inches from the furthest away point on the target's base. This often gives you a very good chance at landing a hit, especially on larger based models like monsters and chariots. Enemy units of infantry are vary depending on size etc but it's a good rule of thumb to go by.

How it should go is that if the cannonball hits a model with multiple wounds it will continue through the unit as long as it kills that model. This is the case of monstrous infantry. Usually most infantry is one wound so that isn't a problem, its assumed that any ones rolled is that model diving out of the way as the cannonball passes through the unit. I don't think anyone has ever intentionally blocked a cannonball with a character. As the rank and file are just not worth the loss.

Normal infantry dont stop a cannomball, a cannon ball will hit all the models even if it fails to kill a lord( highelf prince for example) first, only momsers, monsterous cav and monstrous infantry will stop a cannonball piercing ranks if you fail to kill it, . Note that against dwarves, if youre lucky you can sometimes get 2 or more warmachines since they do NOT stop cannon balls!

That would be a rare occurrence as anybody with an ounce of skill knows you deploy your cannons on either flank for flanking shots and to avoid them getting taken out sequentially by the same unit or model.

I have played plenty of dwarfs that try to deploy all their warmachines around the 5+ ward banner vs warmachines, making it easier for my to shoot through a character and warmachine.. failed look out sir happens!

Now, I roll the d6 for the multiple wounds rule if it's possible for the enemy to save one...

Also note that the Multiple Wounds special rule is applied AFTER saves, not before. So if you hit a Terrorgheist (which has a 6+ Regen save), you roll to Wound, then it rolls for Regen, then you roll to see how many wounds you inflict only if it fails the save.

A model cannot suffer more wounds than it has on its profile.

So while you do technically roll for multiple wounds for each of the hits on single wound models the result rolled is meaningless. The excess wounds are lost.

Think about it like this, when you cause a single hit you cannot kill more than 1 model with that hit.