I understand that for heavy bolters they pay an extra 5 rec points for special ammo (I assume due to the volume and not the caliber as it is the same for all bolt weapons),and that it provies 60 rounds (the magazine of the heavy bolter). I also understand that all heavy weapons come with a backpack ammo supply. One of my players is wondering how much it would cost for a full loaded backpack ammo supply for kraken bolts for example. Would it just be 4 times normal cost (240 rounds is pretty close to 250). Or would it be 5+5 x 4 for a total cost of 40. What would be considered a fair ruling?

Check the FAQ/Errata stickied thread in the main Deathwatch forum, Ross Watson answered this very question as follows:

1) It states on page 159, in the 1st paragraph titled Special Issue Ammunition: “Special Issue Ammunition for Heavy Bolters adds +5 to the requisition total.” This is due to the increased clip size. Which clip size does this refer to? The clip size of 60 of the Heavy Bolter or the clip size of 250 for the Backpack Ammo Supply?
Page 159, second paragraph simply states that Special Issue Ammunition for Heavy Bolters adds +5 to the requisition total.
The +5 applies to all special issue ammunition for Heavy Bolters, regardless of whether it is in the backpack or the weapon clip/magazine.

First off, thank you for pointing me to the FAQ, much appreciated. I didn't know they had one up and running. Second, I just want to make sure I understand, that f or 10 points they get a full backpack ammo supply of 250 rounds of (in this case) kraken bolter rounds. Excellent, I know a few players who will be pretty happy.

That's correct, and this is meant to represent the abstract nature of Requisition. Personally I think the most worthwhile backpack ammo for a Devastator is Metal Storm rounds, and then purchasing a 60 round clip of Kraken or other kind of special ammo, but that's just me.

I would normally agree that metal storm seems to be a wonderful bolt. But it seems the party wants to keep engaging at longer range, or making sure they are in short range to get the extra bonus to BS, and kraken effective gives any bolter +2 to damage vs anything in heavier armor.

devastators can be pretty devastating (pun intended) with regular rounds let alone the specialty ones. only allowing special rounds in clip form and the fact that they have to load the clip (2 rounds IIRC) are both natural balances to the power of the rounds.

I have to disagree with the answer from the FAQ. Special rounds are requisitioned by clip size and the size of a heavy bolter's clip is 60, not 250. As such, I would have the Devastator pay 10pts per 60 rounds. Therefore, a backpack with Kraken rounds would cost 40 requisition.

Dan.