Confused with siege weapons


Rules Questions


Hello All!

I've got a question and I hope that there is an official clarification to it.

Let's assume we have Heavy Ballista. It's located on the top of castle tower and enemy ogres attack castle.
Crew: 3
Aim: 2
Load: 3

So, what does it mean?

1. Each time target moves we need to use 'Aim Actions' or we need to use them only when we switch targets?
2. Round figures (2 to aim, 3 to load) mean
a) that all crew members must spend full-round actions (so if we aim and reload we can fire only once per 5 rounds)
b) or it means that we just need to spend these full-round actions in total (so it would mean that we can fire every 2 rounds?)

"b" seems tempting... but looking to heavy trebuchet or heavy cannon... it would basically mean that those weapons could be fired again every 2 rounds? Seems really too fast. TOO FAST.


Anyone? :)

Scarab Sages

Ultimate Combat, page 159.

Try a more specific example if you want a more specific answer. I have no idea how many crew you have or what training they have. The size of your target matters too.

Scarab Sages

Okay, a more specific one:

You've got 3 humans manning your heavy ballista. The Crew Leader has the Exotic Weapon Proficiency, but no other feats.

1. For aiming, you target a creature. Each time you change your target, you have to start aiming again. There are also penalties on the attack roll if your target is smaller than the ballista (see direct fire siege weapon rules).

2. As I read it, the load action is performed by the crew, so with 3 medium crew working together, they can load in one round if they all perform full round load actions.

Regarding aiming, as it is written, the aiming is entirely done by the "Crew Leader". So, it would take 2 full rounds to aim. As mentioned in the description, the Master Siege Engineer feat reduces these to move actions, so with a double move, you could do this in one round.

As for attacking, again, this is done by only the "Crew Leader" and requires a further Standard action. Given that Ogres are Large Creatures, you'd be at -2 to hit with a Heavy Ballista (because it is one size category larger than the Ogre).

So, your looking at a Shot every 4 rounds, with a normal medium crew and no additional feats. As I read it, Only the Crew Leader is required for 3 of these rounds, so you should be able to have the PCs doing other things during the aiming and attacking phases of the operation.

I will note, that my interpretation of the crew not being required for aiming assumes that the ballista doesn't require any actual movement beyond slight adjustments easily done by one person. If actually rotating the ballista, you'd probably be doing that with movement rules for siege engines, not the aim action. Aiming for a siege weapon is mostly a matter of adjusting for distance you intend to fire - it should already be facing the target when deployed.

If targeting a moving target, I highly recommend using readied actions for the actual attack roll and picking a stationary spot when aiming. A ballista isn't designed to be moved much when firing, so the act of aiming is more in timing when the target will line up with your sights, rather than moving the ballista to target the enemy.


Using a siege engine is really hard without a proper siege engineer (someone with the Master Siege Engineer feat). With it, however, things are much easier.

With Master Siege Engineer and 2 other mooks,
Move Action x3 = Reload
(Standard) Move Action x2 = Aim
Standard Action x1 = Fire

This is one shot per round.

With just 3 mooks (no Master Siege Engineer):
(Round 1) Full Round x 3 = Reload
(Round 2) Full Round x 2 = Aim; Standard x 1 = Fire

This is one shot every other round.

Scarab Sages

How are the "mooks" aiming?


Murdock Mudeater wrote:
How are the "mooks" aiming?

Poorly? Really, though, anyone can be a member of the crew, it doesn't define any stat or skill requirements to just crew the machine. It is the Crew Leader who is the one actually controlling the crew, and their aiming, reloading, etc.

Shadow Lodge

I thought this was going to be about crew leaders who had Confusion cast on them, then told to "attack nearest"


Taking information from here.

Your heavy ballista takes a minimum of 3 crew. One of those crew is the crew leader, who makes the attack roll. It takes two full-round actions by crew members to aim (double that if you have less than 3 crew). I infer that if the target moves from the square, then you have to re-aim (it would make no sense to cost an action to aim at your target's friend beside him, but no action to stay aimed at a target moving 30 feet a round). I am assuming it is a standard action to fire since I can't find that specified anywhere. Next, it takes 3 full-round actions contributed by the crew to reload. Thus, you probably want a crew of 4 so you can start reloading as soon as the leader fires.

The attack roll is dexterity plus BAB. Medium creatures aiming a Huge ballista would take a -4; each extra crew member above minimum reduces the penalty by 2. Alternately, if your crew leader has at least one rank in knowledge(engineering), then you don't take this penalty at all.

Scarab Sages

For the record, the PRD link is here

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