So my group has some questions about the Storm quality. Does it allow you to do a total of 8 hits, or just 4?

It doubles the number of hits the weapon inflicts 'up to the weapon's firing rate' which is the key bit. If the weapon in question has a RoF 4 then it won't inflict more than 4 hits, it just makes it considerably easier to reach the maximum rate of fire.

I don't think the rules are very clear at all.

Firing with a hail of shots, these weapons strike so rapidly that enemies are filled with metal in an instant. This quality doubles the number of hits the weapon inflicts 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 (up to the weapon’s firing rate, as normal).

The bolded part and the text right after seem to contradict one another. A storm bolter (the only weapon in the core rulebook with this quality) has a full-auto RoF of 4. The bolded text says that this quality doubles the ammunition expended, but says nothing about its effect on the weapon's rate of fire (the key limit in the example).

So RAW, it would seem that for the cost of 8 bullets you can inflict a maximum of 4 hits. Which sort of seems contrary to what's intended.

This quality needs to be clarified in the FAQ.

The way this quality is written is unnecessarily complicated. A simpler version would simply read that the weapons score 2 hits for every hit, up to the rate of fire.

I don't think the rules are very clear at all.

Firing with a hail of shots, these weapons strike so rapidly that enemies are filled with metal in an instant. This quality doubles the number of hits the weapon inflicts 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 (up to the weapon’s firing rate, as normal).

The bolded part and the text right after seem to contradict one another. A storm bolter (the only weapon in the core rulebook with this quality) has a full-auto RoF of 4. The bolded text says that this quality doubles the ammunition expended, but says nothing about its effect on the weapon's rate of fire (the key limit in the example).

So RAW, it would seem that for the cost of 8 bullets you can inflict a maximum of 4 hits. Which sort of seems contrary to what's intended.

This quality needs to be clarified in the FAQ.

The way this quality is written is unnecessarily complicated. A simpler version would simply read that the weapons score 2 hits for every hit, up to the rate of fire.

How is it confusing? It has an RoF of 4. WIthout the Storm quality, it can inflict a max of 4 hits, and expends 4 shots. With the Storm quality, it can achieve a max of 8 hits, while expending 8 shots. Essentially each DoS with the weapon counts as 2 hits, up to a max DoS of the weapons RoF.

How is it confusing? It has an RoF of 4. WIthout the Storm quality, it can inflict a max of 4 hits, and expends 4 shots. With the Storm quality, it can achieve a max of 8 hits, while expending 8 shots. Essentially each DoS with the weapon counts as 2 hits, up to a max DoS of the weapons RoF.

I agree that is how it should be, but as written the quality does not effect the weapon's rate of fire.

How is it confusing? It has an RoF of 4. WIthout the Storm quality, it can inflict a max of 4 hits, and expends 4 shots. With the Storm quality, it can achieve a max of 8 hits, while expending 8 shots. Essentially each DoS with the weapon counts as 2 hits, up to a max DoS of the weapons RoF.

I agree that is how it should be, but as written the quality does not effect the weapon's rate of fire.

Because it doesn't effect its rate of fire. It has the same RoF (on paper), its just that the hits achieved with that RoF are doubled. The double the ammo expenditure is to account for it.

It is able to score more hits with fewer DoSs. It can get 8 hits, while only requiring 4 DoSs. It still is always firing 8 shots though. Storm weapons basically represent weapons with a higher RoF, but where the weapon possesses some property that causes it to somehow be significantly more accurate (in this case, a Storm Bolter being a double barreled boltgun).

Again, I'm not seeing how this is unclear. The weapon profile has an RoF and a quality. It performs its attack role in a particular manner, and when determining the number of hits (which is 1 hit per DoS, with a maximum number of DoSs counting towards this equal to the weapons RoF), it simply doubles the hits. As a semi-penalty to this, the weapon consumes twice the ammunition, to represent this.