Forgive the rudimentary nature of this question. I've always taken it for granted that I understood the rules for Penetration as they apply to Cover, but having recently reviewed the core, I feel like there is the possibility of interpreting these rules in two different ways. As usual I used the forum search engine in an attempt to find posts already dealing with this topic, and came up empty.

"If the shot would hit a body location that is concealed behind cover, work out the Damage against the Armour Points of the cover instead, with any excess being applied to the target as normal" - Rogue Trader, pg 246

It is the 'as normal' part that provides for the possibility of ambiguity. This results in two possible interpretations for how Penetration interacts with Cover:

1: The Penetration is reduced by the value of the cover prior to any damage being applied to the target's Armour. Example: A Rogue Trader fires a Plasma Pistol with Penetration 6 at a target wearing 5 Armour and taking cover behind thin metal with a cover value of 4. The Plasma blast tears straight through the Cover, leaving 2 points of Penetration that reduce the target's final armour value to 3.

2: Cover and Armour are handled completely separately. In the above example, the Plasma cuts first through the Cover, then effects the Armour 'as normal', completely cutting through it as well.

I'm pretty sure the right answer is #1, but if you want a definitive ruling you should send your question to the Rules Question adress at the very bottom of this page.

fulcan said:

Your cover has 4 armor
+You have 6 armor

Your cover + your body is hit for 8 damage with 0 penetration

Your cover absorbs 4 of the 8 damage. The excess is 4, which is applied to your armor of 6, nullifying the hit.

Your numbers are all wrong, so you're just confusing the issue.

The attack has 6 Penetration, completely bypassing the Cover of 4 AP, and also bypassing 2 pts of the armour (originally 5), reducing it to an effetive 3.

I believe option #1 is correct.

Didn't White Lycan just give a random practical example for option #1?

Which, I agree as well, would likely be the way it is supposed to work. "Excess" means that cover must be able to reduce the power of the attack, whereas "as normal" refers to the remaining damage being applied to the target as if it were a standard attack, which means it has to overcome armour + TB.

In essence, cover would thus merely work like a third layer of damage negation.
It is also the most logical application of how it would work realistically … although I admit that this must not mean much.

Because the question is "does Penetration apply twice when shooting through cover?", an example attack with 0 Penetration doesn't exactly help us much. I originally thought #1 was probably correct, but thinking about it, I'm leaning toward the Penetration applying separately and fully to each thing in the way… that would make Penetration better than Damage against hard targets, which using option 1 it isn't. The only difference between custom ammo adding +2 Damage and +2 Penetration is that if your target is unarmored, the Penetration ammo (manstoppers, I think) is no better than standard…

I'll reread that section of the book and see what feels right to me, anyway. Thanks for bringing this up, fulcan, it's interesting to say the least

Hmm, I see where you're coming from. The wording as quoted by fulcan also leaves room for interpretation, given that it specifically only mentions "Damage" but not Penetration … I guess I just automatically took the latter to be included in the former, yet on second thought that need not be correct.

Yeah, I'm really liking that interpretation, as it creates a situation where Penetration can be better than Damage (where otherwise, Damage is ALWAYS the equal or better option). It creates three distinct attack scenarios…

A) Your target is unarmored and not behind cover, where Damage is the only thing that applies and Penetration is completely useless.

B) EITHER your target is unarmored and behind cover, OR your target is armored but not behind cover, where Penetration and Damage are equally useful, up to a Penetration maximum of the AV of your target (or his cover), with no max on Damage.

C) Your target is armored and behind cover, where Penetration is twice as effective as Damage up to the lesser of the two AVs, then equally useful up to the higher of the two AVs, again with no maximum usefulness to Damage (at least, short of 11+ Critical Damage).

I just haven't had a chance to actually open the book and make sure it's solid by RAW, but the quote in the OP certainly seems that way. Note that I'm pretty sure you should still reduce the Damage for the cover (and the armour) if the Penetration isn't enough to fully negate it - like if you have an AV of 6 and hiding behind cover with AV 5, and you're fired upon by a weapon with Pen 4 - the damage of the weapon should be reduced by 3 before it gets to your Toughness Bonus.

For the sake of simplicity I figure it works as follows:

(A+B) -C = final armor value to be added to toughness bonus to generate figure for mitigating damage

A being the character's armor, B being the value of the cover to the hit location and C being the penetration value of the weapon he is struck or shot with.

Now an equally nubby question I'm not 100% sure about, does penetration negate the protection of the character/NPC's toughness bonus if it already fully exceeds the character/NPC's armor value? Personally I don't think so but I don't remember reading anything that said one way or the other.

Pen does not affect TB at all. Only damage.

Amazing Larry said:

Yeah, this is basically the nuts and bolts of option 1, and is how I have always assumed it worked, and consider it to be the intention.

I think the tricky part is that the book assumes that cover means chest high wall because it explicitly says that cover applies to legs and torso, obviously I just go with that when the cover is a chest high wall or a crate or fruit stand etc but if it's not like say if it's the corner of a building or a column or something like that I try to get it established before the attack roll exactly how the player or NPC is positioned in that cover and from there decide on three body parts to be exposed.