As the group's devastator I am fully aware of how gear dependent people can be for damage.  When the GM rolls out a boss villain with a huge weapon, my first thought is "I shoot the weapon."  No more demon sword for you Mr. prince.  No more venom cannon for you hive tyrant.  Since one krak missile isn't going to to take them down I find it is a great way to increase the party's survivability.   However, we haven't been able to find any rules on toughness or structural integrity of weapons. Do any of you know where I can find rules or guidelines for this?  Or am I looking at it having to be completely house-ruled?

From memory the only time weapons can be destroy is when a SM is actively parrying with a energetic weapon.

Now using a call shot, you might be able as GM, to know if a certain amount of damage can release a weapon from the grip of it's bearer.

With the same action you have to determeine by yourself if the amount of damage is high enough to destroy a weapon.

This is entirely up to the GM, but I applaud any GM who would try to make this happen (and do it fairly). Keep in mind it shouldn't be an easy thing to do…

First off its a called shot (its as difficult to pick out as an arm or leg) - thats -20, then you are specifically targeting a small object (You can't simply shoot at the part of the siluete where an arm is, you actually have to focus on the small weapon) - so it should be another -10 or -20 to hit. Then there is range and conditions to consider. Next the target weapon holder gets reactions if aware, and finally the GM decides if the damage done is sufficient to hurt the weapon in question.

The only guideline for weapon toughness I can think of is that a Daemon weapon in Black Crusade has 20 AP and 5(?) wounds, if you want to measure it out mechanically. Personally, I'd fudge it for drama's sake (and I have, I've had Heavy Bolter Mounts get their ammo cooked and had hormagaunts rip the storm bolter off a Rhino with some rough numbers and a bit of "eh. seems about right"), but that's just me. :P

 Actually did this - Raven Guard Techmarine with a Stalker Bolter wanted to disable main gun on a Hammerhead by shooting into its barrel.  I said, ok, that's going to be -40 to hit, and it worked really well.  Added a real sense of tactics.  Of course, sometimes things like that can take all the fun out of an encounter (you shoot the daemon prince's sword, the sword shatters, the daemon prince says shit and dies), so I'm only going to allow it when players specifically ask to rather than coming up with a general rule.  But it's a great idea and should be explored.  

AlphariusOmegon7 said:

If you break a daemon weapon doesn't a daemon come out of anymore? That used to be the case, so disarming a daemon prince in order to fight a daemon prince and a greater daemon is not a good strategy.

That's how it works in Black Crusade and the fluff, so I'd say that yes, a Daemon comes out of a Daemon weapon.

Seems to be a house rule thing.

I'm not very familiar with the Deathwatch system, but I've been a GM for a while, and I can tell you right now that "short-circuiting" a major fight in this manner is not conductive to good fun. Sure, it's going to score you some "Whoa, dude!" and high-fives as what was supposed to be a boss-fight turns into a fight against a cripple: Your friends get to pull all your fancy moves and lay the beat-down on a guy that can't seriously harm you. While that can be fun in a school-yard-bully sort of way, it doesn't really convey an atmosphere of epic triumph in the face of overwhelming odds, now does it?

And the next time when your GM needs to provide a challenge, suddenly all your weapons don't work either: Using the same house rules the bad guys evil minions can crack your precious toys and you're left to carve your way through a Hive Tyrant using only your Bletcher's gland and combat knife. And even if that's fun, the GM can pull those tricks as long as you can, except his guys never miss…

That being said, there is a Talent called Disarm that deals with the issue of, well, disarming the enemy.

-K

Nothing quite like taking out a venom cannon only to find out just how good the monster is in melee.  Oops.