Is it possible to mount two heavy bolters on a forearm and use them simultaneously (with two weapon fighting). Also, the RoB supplement allows you to add one weapon upgrade to a weapon. So theoretically, one could use two heavy storm bolters. My questions: 1) is this possible or did I make a critical mistake? 2) Is there any reason, if it's possible, why a devastator wouldn't use it?

As per the rules you can only forearm mount pistol-sized weapons or the aux. grenade launcher. So this would not be possible, no.

fleshbearer said:

Let me guess, you don't nor have ever played 40K, right? As stated, "pistol sized weapons".

Actually, even though what you said makes perfect sense, the wording of the forearm mounting is ambiguous. It might seem 'obvious' to read it as pistols, but logically, it could also be interpreted as 'bolt, solid ammo (?) and plasma pistols', implying bolt GUNS etc and plasma pistols.

Oops....hit post too early. I don't have the book on me at the moment, so if it clearly says 'pistol sized weapons only', then it's a non question.

Wirst mounted Bolter/Storm bolter = OK. Wirst mounted Heavy Bolters = Wake up

Vendettar said:

But...that means I can't use my twin arm-mounted Heavy Bolter and Assault Cannon combo.

Seriously, though, I could probably see allowing a basic bolter (not sure about the storm bolter) even though the book says it's restricted to the pistol type and auxiliary grenade launcher. Personally, I recommend going in Predator-style: put a plasma pistol on each shoulder and burn down anything that gets close.

Yeah, I wasn't seriously suggesting arm mounted HBs...it was actually a friend of mine who suggested it without reading it properly. Oh well, now I'll just have to use the arcane option from ROB to requisition a HEAVY STORM BOLTER. *bwahaha*

fleshbearer said:

So you know, a devastator making 2 hits per degree of success would be... an army-killer. However... I think a storm bolter of any kind (pistol, basic, or heavy) generates the same number of hits than a regular one, just each of those has two bullets instead of one. Following this line of reasoning, it would have no effect whatsoever against hordes, because they don't care if you are firing at them with a lasrifle or a lascannon...

And a Heavy Storm Bolter would require two deathwatch suspensors. I think it's cheaper to don Terminator armor with an assault cannon, compared to all you have to get for that one XDDD