Peek-a-boo! (Advanced Tactica: Vehicle Shooting and LoS)

So sturgard wrote me with another interesting question. It seems an IG player in his area has picked up several Hydras. These are then hidden behind other tanks/cover such that the guns poke out and nothing else. The player then traces LOS from the end of the barrel, often removing cover saves from his targets. In return, he claims that the Hydras can't be shot back at unless you can draw LOS to the hull... and even then he's claiming Obscured saves. I've heard a similar complaint leveled at Marines using Land Speeder poking over Rhinos and Dreadnaughts firing around the corner of a wall.

It's a "I can shoot you, but you can't shoot me." thing. The question is, is this a clever abuse of the rules or is someone getting cheated?

First let's look at "I can shoot you..". When drawing LOS from the vehicle, you need to be aware of the nuances of BRB, page 58, "Vehicles Weapons & Line of Sight". The key thing here is that the weapon must be pointed at the target and then LoS is determined "from the weapon mount and along the barrel." This is NOT the same as drawing LoS from a single point like the eyes of an Infantry model. The weapon's MOUNT must be able to draw LoS and you resolve it's ability to ignore cover from there. So sticking just the barrel around cover does not allow you to draw LoS.
There's also a fun side effect of this... a common RL counter to tanks or emplacements is to "get under their guns". Simply, it is keeping yourself safe from fire by getting out of the traversal arc of the gun. 40K allows for a 45° vertical traversal of mounted weaponry. Additionally, a model cannot shoot backwards, curving around an edge, nor point a gun through it's own hull. Give this a little thought and maybe throw down some models to try it out. Tall models (Skimmers on flying stems, Valkyrie, Titans), long barrels (Hydras, Vanquishers, Hammerheads) or turret placement on long/large models (Razorbacks, Land Raiders, Chimera, Baneblades)... you'll find they all have this type of issue against Infantry in close quarters. If the tank doesn't back away, the Infantry will often gain cover saves or even be untargetable due to being "under their guns".

Now let's look at the other half, "...you can't shoot me." BRB, page 60, "Shooting at Vehicles has a similar caveat in targeting to allow extra bling, decorations and other modeling to be done to a vehicle without in-game penalty. The rule is that you trace LoS to the vehicle's "hull or turret" but ignore "the vehicle’s gun barrels, antennas, decorative banner poles, etc.". The key thing here is that you ignore the gun's BARRELS, not the casing, weapon mount, sponson, targeters, or any other such items. Just as an extra touch, what is a sponson but a side-mounted turret? So you're doubly covered here. As long as your opponent is obeying the rules above for shooting at you, then you can shoot back at them.
But what about being Obscured? For determining Obscurement of a vehicle, we go to BRB, page 62, "Vehicles and Cover - Obscured Targets". To gain a cover save, they need to cover "at least 50% of the facing of the vehicle..." The common mistake here is that people often apply the LoS rules and ignore the weapons, sometimes even ignoring the weapon mount too. This can make a HUGE difference when looking at a tank like the Basilisk or Hydra. Obscurement is based off how much of the total model you can see, not just how much of the main hull is visible.

A couple other common mistakes in this section:
1. When shooting a vehicle, weapons that cannot hurt the tank are ignored for purposes of determining cover. This can cut both ways, so be careful with where your anti-tank is positioned.
2. When a vehicle is firing, the target's cover saves are determined:
a. ignoring weapons that do not have LoS and/or do not fire.
b. with each gun on the vehicle counting as a separate model in a unit; needing a majority with clear LoS to ignore cover.

Hopefully this has given you all some fun ideas. If anything doesn't make sense, please let me know and I'll try to expand or provide illustrations. (Actually, illustrations may be forthcoming anyways...)

Image is a Funtrak paintball tank, acquired from 800hightech.com.

Addendum: A couple of people have asked me what I got as my Ard Boyz prize. I picked up a Land Raider Crusader/Redeemer. There wasn't a whole lot of Eldar stuff I wanted in that price range and my Wolves certainly appreciate the support.