Hi there.

Here's a question. How much is the ammo consumption for the storm bolter? If I succeed on all the shots using semi-auto burst does it take 4 or 8 ammo?

8.

Corebook, p.144: "This Quality doubles the number of hits inflicted on the target and the amount of ammunition expended. For example, when firing a weapon with the Storm Quality in fully automatic mode, each degree of success yields two additional hits (to a maximum of twice the weapon’s Full Automatic rate of fire)."

Errata, p.8: "Question: Does a weapon with Storm generate a maximum number of hits equal to the ROF of the weapon, or double the ROF?
Answer: Double the ROF."