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D&D 3E
New weapon design 
4th-Sep-2006 07:27 am
I'm about to start as a player in a 9th level campaign, where all the PCs are mercenaries. The setting seems to inlcude early gunpowder weapons, and I thought it'd be cool to have an artillery piece. I'd like some input on the design: Is it reasonable/balanced/etc?

+1 Gnomish Mortar
Masterwork artillery piece (exotic weapon)

120mm (4.7") smooth bore muzzle-loader

This weapon has firepower almost on par with a light catapult, with far better portability - at greater, but not (quite) ruinous cost of operation. It consists of a 1m (39") barrel, a wide base-plate (intended to diffuse recoil into the ground), and an adjustable targeting apparatus, all of which are made of iron or bronze. The precision requirements of a firearm require all artillery to be of masterwork quality.
Any creature holding a mortar as it fires (rather than bracing it firmly against something) must make a DC14 strength check or be thrown backwards.
There's a 5% chance that a shell will explode as it exits the barrel, causing damage effects centred on the square immediately in front of the weapon. Unless they employ a torch on a pole, or other such device, the operator is considered to occupy the same square as the weapon at the time of firing.

Range: 150', no minimum (though at least 30' is recommended, there's no mechanical reason why you can't fire straight up)
Crew: 1 person
Load: 1 full-round action, uses 1 shell & 2 pints of gunpowder
Aim: 1 standard action
Fire: 1 move action

Ammunition & damage:
Ammunition consists of 120mm(x150mm) shells, which have a metal base & wooden cartridge. Inside, the cartridge is divided in two: One half holds a glass container of alchemists' fire, and the other holds 1pt of flour. The cartridge is crushed on impact, releasing a cloud of flour into the air, which is promptly lit by the alchemists' fire.

Each shell does 2d6 fire damage in the square it lands in, and 1d6 in all adjacent squares. Flammable items within this range catch fire. The explosion does an additional 1d3 bludgeoning damage to small or smaller creatures which are flying within the area of effect. Beings in squares adjacent to the explosion, but not in its centre, may make a DC15 reflex save for half damage on all rolls.

Under moderately windy conditions, the fire effects may be moved from one side of the impact site to the other, but the square of impact still takes 2d6 damage. Severe winds (30+mph) will blow away the dust cloud before it can ignite; handle as though only the alchemists' fire were launched.

Due to the relatively 'slow' explosion, catapults with boulders are still preferable for demolishing nonflammnble fortifications. However, it makes an effective antipersonnel weapon, even under those circumstances. Since a unit of ammunition is at the heart of an explosion, it's obviously not recoverable.

Unit cost: 800gp
Unit weight: 30lbs
Ammunition cost: 10gp/shell
Ammunition weight: 3lbs each, 15lbs/5
A batch of 5 shells can be made in a week. This requires a DC15 craft(ammunition) check. Components, such as gunpowder & alchemists' fire, require their own checks & creation time.

Special attack modifiers: (same as catapult attack modifiers, included for speed of reference)
No line of sight to target square: -6 atk
Successive shots (can see location of most recent misses): Cumulative +2/prev. miss, max +10
Successive shots (can't see location of most recent misses, but observer providing feedback): Cumulative +1/prev. miss, max +5

Historical notes: The earliest known use of mortars was by the Chinese, recorded in 1132. They consisted of a bamboo tube, gunpowder propellant, and a projectile. Mortars with a metal barrel appeared around 1270. In and around this time, the average soldier still used a sword.

Anyone who doubts that flour is explosive should look up 'flour explosion' - the wikipedia article is particularly enlightening.
4th-Sep-2006 05:58 pm (UTC)
In the real world, shells invariably have metal casings designed to fragment upon explosion, creating shrapnel. For the +1 Mortar, I'd model this with metal casings and piercing damage from the shrapnel (and give it a wider area of effect), dropping the bludgeoning damage.

I'd leave the fire damage as-is.
4th-Sep-2006 10:21 pm (UTC)
I thought about that. The problem is, that sort of explosion would require the cartridge to be on fire inside, when it was fired, or have a lit fuse (which, under the circumstances, would go out in midair). I don't want 'held the grenade too long' type issues. ;)
4th-Sep-2006 06:06 pm (UTC)
I'm not so sure about this.

Personally, I wouldn't be the one opperating the thing, and if any of my party members had one I'd be likely to stand extremely clear of him, and whatever he decides to aim at, at all times.

One thing I think you should add, however, is a Reflex save (DC 15 or thereabouts) for those in the squares adjacent to the one that gets hit. Otherwise it looks like a nice little boomstick, to me.
4th-Sep-2006 10:25 pm (UTC)
That's a large part of the point, yes. It's a man-portable siege weapon, and you can't call it a proper gnomish weapon if there isn't some chance that it will blow up in your face. ;)

I did list a reflex save, but perhaps wasn't specific enough. Fixed.
5th-Sep-2006 01:42 am (UTC)
I would require longer to load, 6 seconds seems awfully quick. 1 shot/2 rounds for a seige weapon is pretty mean. Since it is a seige weapon I would shift some damage to seige style damage since the impact should do the damage. A vial of Alchemist Fire would shatter upon firing a shell that large, no need for something that clever... A 3lb hunk of metal that large would destroy anything foolish enough to be in its way assuming a decent muzzle velocity.
6th-Sep-2006 06:07 pm (UTC)
Good points. I've increased the reload time to two rounds, which would put firing at three in the best case.

I probably will drop the explosive shells. Elsewhere, someone pointed out that the weapon itself could explode if hit with a fire attack while loaded. A critical failure in that case would probably kill me. c..c
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