Hiyas:

Quick questions:

Can an Astartes bolt weapon be used underwater (fired, of course )?

How about a chain weapon?

Thanks!
L

I would say everything can. Even flamers. The only things that should really lose effectiveness are SP weapons.

Hiyas!

Is there some actual precedent for this (like in novels, etc.)? I've searched the Holy Books but found nothing of the sort.

Thanks!

L

Bullets will fire underwater. Yes they will. They'll even fire in the vacuum of space.

This is because bullets do NOT need air (or oxygen) to work. Gunpowder is an explosive, which means it contains its own oxidizer (oxygen).

Rockets also do not need air to function. Rocket fuel contains its own oxygen (if liquid) or oxidizer (if solid, like a bolt round).

Flamers DO need air to function. Their ammo is fuel and does not contain its own oxidizer, in the absence of oxygen it would not light. (The water would put out the pilot light anyways if under water.)

The problem with firing bullets (and bolt rounds) underwater is the pressure and friction of liquid water is much greater than gaseous air. Fired into or in water a bullet would transfer all of its energy into the water before it travels more than 3 feet. It would be just as if it had hit a solid wall. A rocket would go farther than a bullet, even thoughit transfers its energy into the water like a bullet, since it generates additional momentum from its propellant. Even so, the friction of the water would drop the acceleration of the rocket to a tiny fraction of normal but the burn time of the motor would not change. Your rocket that travels mach 2 and up to 5 miles would only go 10mph and go 20-30 ft. in water (exagerated for emphasis, I don't want to do that kind of math), that is if it didn't smash itself apart when it hit the water (which it would).

Now, nuclear submarines can launch their rockets from underwater and they do attain decent speeds. But their launchers are specifically designed to work underwater, using steam and air pressure to propel the missile to the surface of the ocean where its rocket motor then lifts it up. Torpedoes, likewise, are specifically designed for underwater movement, with high powered proppellers moving water to accelerate and a different design and shape than aerodynamic projectiles since hydrodynamics function differently than aerodynamics.

Hand to hand weapons would function, but slashing or chopping weapons would be at a disadvantage as the water's friction would make it very hard to move them as fast as you need to for them to work. Thrusting weapons don't deal with as much friction and would work pretty well underwater, at least better than slashing weapons.
As for chainsords, as long as the motor won't short out it should still function. Swinging it would be even more difficult than a normal sword since they are fatter (more friction) and the movement of the teeth would likely give you some problem. But if you just slapped it up against something and then turned it on the teeth should bite and saw nearly, if not better (water is a lubricant and coolant), as well as it does out of water.

Hiyas!

I thought that there was some "technomagick" explanation to bend the laws of physics regarding this subject (that Astartes' weapons were able to do this), per the canon.

Laws of physics still trump, then!

L

Older fluff had bolt weapons firing perfectly underwater. The closest I can get to new fluff indicating it's possible (off the top of my head) is a reference to Space Wolves botching a drop pod assault against a Tau facility on an oceanic world and then fighing modified crisis suits underwater (Planetstrike reference).

Personally, I'd rule that astartes Bolt weapons would fire without penalty, melee weapons work as normal, other weapons on a case by case basis.

Imagine there's a family on a nearby forge world. This family, for a hundred generations, has had one task. Their hands are replaced with holy scriveners at the age of twenty five, that being one of the sacred squares of the Omnissiah, and they are put to work. Their task is to inscribe Bolt shells with the blessed pattern of the Omnissiah's Injunction against the Depths. That family, their overseers, the menials that deliver theose bolt shells to the Astartes, and the Astartes themselves are all completely oblivious to the fact that 28,000 years ago a savant mathematically developed a near-microscopic pattern that, when etched onto a Bolt Shell, allows it to create a small bubble of vapourising water ahead of it that allows it to fire underwater without penalty.

tl:dr - if it seems unreasonable, you can always pull out the STC trump card

There are bolt rounds that are designed to operate underwater. These are essentially miniature torpedoes. I'm pretty sure any Astartes force being deployed to a world where underwater combat is likely or possible would be issued these bolt rounds.

Although, Astartes (read: your players) would have to remember to switch their normal ammunition for them or be suprised when their rounds run out of steam inches from their barrels.

herichimo said:

That's a little too simulationist for me, and that's saying a lot.

Well thats how the Astartes do it. "Simulationist" aside they do use torpedo bolts for underwater fighting. You'll have to look back a few years before guys like Andy Chambers and the original ilk left, but thats how they did it.

Yep knowing the current DW trend anything that can be specialised is. However, Astartes weapons have already been discussed at length and it certainly seems that part of there character is an amount of redundancy. Bolters specifically are designed to work almost anywhere. Bearing in mind the limits already set out there nothing to say that a rocket motor couldn't couldn't also work underwater (if it's designed to do so).

I'd go with a mixture, any weapons fired under water (that can be at all) would do so reduced range and at maximum depths. This especially includes Astartes Bolt weapons, specialist bolt ammo can be requisitioned that work at full ranges and at greater depths.

Energy weapons in general can't. Meltas and Plasma's basically explode as fired, Flamers, although I believe the prometheum does burn in oxygen free environments will not ignite underwater. Special flamer fuel might be available but I would think that the range would be heavy reduced. Las Weapons probably have a heavily reduced range.

SP weapons may fire with a reduced range (some may not fire at all), although you'd probably find that the weapons mechanism does not function reliably. Automatic mechanisms would not normally be configured to expel cases or blowback with enough force to fire rapidly. Probably can get ammo that removes the penaltys but does less damage.

Launchers probably can't fire without special ammo.

I doubt powerfields work underwater. If they do the crackling energies probably don't make it easy to use and use power at a phenomenal rate.

herichimo said:

That's how they do it in the novels, sure. I'm not really surprised that FFG opted not to carry over "special underwater-only ammo" to an RPG. Waste of wordcount, adds relatively nothing to the game except another rule to remember.