We played our first session last weekend and had a blast. The only thing that caused a little bit of confusion is damaging hordes.

For example : The blood angels devastator has a base BS of 48. If he aimed and used a full autoburst against a horde, his modified BS would be 98. If he then rolled a 25, he would hit with 7 degrees of success. Based on the full auto burst rule, this means 8 hits. But his Unrelenting Devastion inclicts 1 extra point of damage for every hit, meaning the hordes magnitude would be lowered by 16.

Is this correct ? Is there any need to roll the actual damage for each shot?

Yup, that's correct.

There would be a need to roll damage if there was any roll that (due to a crappy weapon or a more powerful enemy with lots of armour and toughness) didn't inflict any damage at all.

Jerre said:

Based on your example above, the player should only have a modified BS of 88? Base BS 48 + 20 Full Round Aim + 20 Full Auto = 88. Then that would mean that he hit with the roll of 25 and scored 6 DoS (35, 45, 55, 65, 75, 85) for a total of 7 hits. So that would equal 14 levels of magnitude lost using Unrelenting Devastation instead of 16.

Is that accurate? I don't have the book so I am using Final Sanction as my reference. Does your example above include a bonus of 10 to BS due to the size of the horde to make the modified BS 98?

Yep, it'd be 14, unless you have a +10 size modifier for the Horde too.

I think its:

Base 48 + 20 Full Auto + 20 Horde size + 10 Short Range (75m) = Effective BS 98

At least that is what the Devastator was usually getting when I ran part 1 of Final Sanction on Sunday.

Thanks for the responses!

I think I accidentily included the +10 bolter mastery of the tactical marines.