I had an incident recently where I was trying to dislodge the remains of a Tactical Squad from an Objective. They were out in the open and I fired at them with 4 Boltguns and a Plasma Gun all within rapid fire range. So, that's 10 shots against three guys. My first roll is lucky, I only miss with one Bolter. Now, see if you can guess how many wounds I caused? If you guessed 0, you just won a cookie.
I'm going to mathammer this is two ways. Firstly, the whole event of shooting and then secondly what should happen with 9 hits.
Bolter Wounds = P(Hit) x P(Wound) x Number of shots
= 2/3 x 1/2 x8
= 8/3 (just under three wounds)
Plasma Gun Wounds = P(Hit) x P(Wound) x Number of shots
= 2/3 x 5/6 x 2
= 10/9 (just over one wound)
The Plasma Gun wound and a Boltgun wound would go on one guy and then the other two would take a 3+ save each. Since we've rounded in our favour for the wounds, lets be kind and say they both survive. Still, mathammer kills one more than I managed to.
Let's see what should have happened after I rolled 9 hits:
Bolter Wounds = P(Wound) x Number of hits
= 1/2 x 7
= 7/2 (3 and a half wounds)
Plasma Gun Wounds = P(Wound) x Number of hits
= 5/6 x 2
= 10/6 (just under 2)
Lets call it 2 AP2 wounds and 3 Ap5 for the sake of simplicity. One guy gets both AP2 wounds and the other two guys have three 3+ saves to make between them failing one. So, two dead.
Hmm, maybe my dice are just cursed.