Okay, so my mind is probably over-complicating this but I'm curious about what exactly the attack roll is on a cannon. Is it based solely on the crew leader's ranged attack roll? The whole crew's attack roll? Does full AC factor in or is it a touch attack like firearms... (I realize this would be ridiculous but full plate in my mind does not stop a cannon ball from killing a character...)
Here's my reasoning... (I'm using a pirate crew from leadership)
A crew of 5 mans a large cannon, the crew leader has ranks in knowledge (Engineering) so the -2 for size category doesn't factor in (also, extra crew). The crew leader has a ranged attack of +4, basically giving the cannon an average of 14 to attack. Direct-fire siege weapons attack objects, creatures etc.
Also, indirect-fire weapons use the BAB, the knowledge engineering, and modifiers for proficiency and a table based on whether or not a hit was made. So with that same character a roll to attack a square using say a catapult. the DC to hit is a 20, the character is proficient so no penalty, he has a BAB of 2, +5 for having ranks in know. engineering, also he GAINS accuracy as he fires successive shots. Effectively he has a +7 on the first attack and it only goes up from there (assuming the same square target).
I can understand siege engines being wildly inaccurate so I'm really just curious to know. In reality, there are similar principles to aiming cannons and catapults, adjustments are made on misses to make shots more accurate, which is what the in-direct fire adjustment table represents...
Also, cannons are tied for the most expensive siege weapon in their size category (with bombards, which are essentially a type of cannon), and don't do a hell of a lot more damage on average than in-direct fire counterparts.
TLDR: What makes up a cannon's ranged "to hit?" and Is it a touch-based attack as other firearms? (The rules call them firearm siege weapons, but don't state anything specific about what a firearm siege weapon does other than have a misfire rate and a chance to explode.)
Normal attack roll means... normal ranged attack roll: BAB + Dex mod + any modifiers.
And no siege engine attacks "touch" AC. You can rule otherwise for a cannon within a certain range (first range increment?) but thems not the rules.
Yeah, I get that, the reason why I got confused was that the text says that direct-fire siege engines are "more" accurate when in practice that's not really true... particularly when indirect fire siege engines get more accurate with consecutive shots.
Anyone else? Facts? Opinions? I discussed further with another player and the DM and we're all sort of suggesting changes to make Direct-fire siege weapons more accurate as per the implied text, but we have a rules lawyer in the group and I'd rather find some sort of standing on this.
After further discussion we sort of came to the conclusion that it doesn't really make sense for any siege weapons to be MORE accurate per se but the low accuracy of direct fire siege weapons and the fact that you're supposed to aim at the desired target makes them ineffective in battles. One of the ideas tossed around was that they should have a similar table to indirect-fire siege weapons as the same real world mechanics of shooting and recalculating aim apply to both (and really cannons don't fire in a straight line, but an elongated arc).
With the current rules, cannons are highly effective at hitting ships and buildings but crappy at hitting anything else, which makes some sense. However, why not allow them to aim at a square like indirect siege weapons?
It's not like this is the most important rule in the book, it's really only come up because we've recently had a sea to land battle and it was an interesting combat but the way we used the cannons was flat out ineffective and a huge waste of gp... if they work exactly as we assumed they do.
I believe that just hitting a square is AC5 - if the siege ammo is large enough, that could be all you need - though that would be too powerfull for character combat, but might be accurate against e.g. a ship.