Pathfinder 1E Firing cannons

[Pax_Valentine]

I have a character with an airship that has cannons on it. what do i add to my attack rolls for firing a cannon? do i add my dex + base attack or knowledge engineering? and what to i roll against on creatures their normal AC or touch? my character is a lvl 12 siege mage.

 

[Hitcher]

Within my campaign I have ruled the following:
You need Weapon Proficiency Exotic (Cannons) to fire a cannon. You also need a Crew to operate your cannon(s). As firing a cannon does not neccessarily involve much dexterity I let my player choos if he adds his dex or int towards this (as the calculations for firng a cannon may be somewhat complex), but regarding rules as written they would need dexterity.
Keep in mind that you operate a cannon not alone - so you have some minions nearby that help with aligning, reloading and such - who can take the aid action to help with your attack roll.

The Attack Roll itself is against the normal AC. These weapons are designed to work against other ships wich tend to have a quite low AC.

In my campaign I have given the "Profession: Gunner" the ability to increase the damage of the cannons he commands. Once per Target he can designate it as a target, and roll his Profession Skill against the AC of the target. For each multiple of 5 above the AC the Cannon(s) under his command get +1 Damage Die. This counts as a full round action, with the exception that the "Gunner" himself can fire one cannon by himself within this action. This buff can effect up to 5 cannon crews, which have to be in hearing range of the Gunner. But - this is a house rule

 

[Starfox]

In general, cannot are used just like any other weapon. That is, the attack roll is BAB + Dex. Because it is a firearm, attacks in the first range increment are resolved as touch attacks.

Additionally, there is a penalty for firing canon based on the relative size of the cannot and the gunner, and there is usually a long reload time. Extra crew can help mitigate this.

Check out the rules

http://www.d20pfsrd.com/equipment---final/weapons/firearms

http://www.d20pfsrd.com/gamemastering/other-rules/siege-engines

 

[Celebrim]

I have a character with an airship that has cannons on it. what do i add to my attack rolls for firing a cannon? do i add my dex + base attack or knowledge engineering? and what to i roll against on creatures their normal AC or touch? my character is a lvl 12 siege mage.

This really depends on the rules set. My take:

In general, I think firearms are best modeled by giving them an accuracy and penetration statistic. The accuracy on a breech loading smoothbore cannon would generally be a negative number, they aren't designed to engage man-sized targets. The other number for a firearm is penetration. Penetration is the number deducted from the target's armor bonus to AC. For a cannon, the penetration is quite high - armor is relatively ineffective against them.

So for a typical say 6lb or 8lb non-rifled light cannon, I might have Accuracy: -3 and Penetration +10, with a range increment of 200 ft. and a maximum effective range of say 20 increments. Rate of fire would be 3 with a crew of 5, adding one to rate of fire for each missing crew member. I'd probably also assess an additional penalty to accuracy against a moving target with less than the ideal crew. Reload Damage would be on the order of 3d6+9, critical range 19-20/x3. For a 12lber or other medium weight cannon, Accuracy: -4, Penetration: +12, range increment 300 ft (maximum 20 increments), rate of fire 4 with crew of 6, Damage: 5d4+12, 19-20/x3.

Cannons can also be used as Area of Effect weapons by loading mini-balls or canister shot. I'd model this as a targeted burst attack in the case of mini-balls or a narrow cone attack out to 1 range increment in the case of canister. All in the area of effect are attacked, but penetration is halved, and accuracy reduced by -2 beyond say 30'. Damage from either attack is just 3d6.

The other question is whether your character is actually proficient in using a cannon. Cannons can be added as an exotic weapon proficiency, but I also assume proficiency with siege weapons if the character has at least 5 ranks in Knowledge (Engineering) or equivalent and cannons are common to the societies technology level. I presume a siege mage has at least some ranks in whatever skill involves knowledge of laying a siege and siege engines. Without a proficiency, assess the usual -4 penalty.

Note that at standard engagement ranges - say 800 yards - the typical target of a cannon shot isn't a character, but an entire unit of troops, building, or ship. Anything other than a immobile colossal object is a very difficult target at such a range.

 

[MarkB]

If the airship has cannons in fixed emplacements, like a traditional sailing ship, then they won't be built for independent aim or individual fire. Instead, their intended usage will be in volley fire, and the captain will judge when the ship is correctly positioned to attack its target before giving the order to fire.

In that usage, an accurate barrage depends upon the actions of the officers and the gunnery crews all working in concert, to bring the ship's guns to bear quickly, then order the attack at the opportune moment, then carry out that order in timely fashion to unleash a concentrated bombardment.

There may be smaller deck guns that can be individually targeted, but they'll tend to be smaller and less powerful than the main guns.

 

[Starfox]

While fixed guns have only a narrow angle in which they can aim, they can still be aimed in the vertical, and the firing can be timed more or less well. So it is still a matter of the gunner's skill to fire these weapons.

This is completely different from the fixed-forward guns of aircraft, where you literally aim the weapon by turning the entire plane.