Today's example is for Renegade Scout. 

I trust most will be familiar with how 40K combat works, so we can examine this by looking at how it differs though I will try to explain in details for those not familiar.

Step 1 - Firing basics

We have a squad of soldiers (standard Unity Grunts) firing at a rebel unit consisting of similar troops. 

For the purpose of combat we need to know that they have a Shooting Skill of 3 and a Defense of 3.

Being a high-tech sort of outfit, the squad has 4 soldiers with laser rifles and 1 soldier with an auto laser. They are all wearing Light armour with an Armour rating of 2. 

They are 10" from their rebel targets putting them within close range for both weapons (Laser rifles have a close range of 15", long range of 30" while the auto laser reaches to 20" and 40" respectively). Lasers do not have a hit modifier due to range. 

Laser rifles have the Rifle trait which increases their long range by 4" when stationary but that won't matter here.

Step 2 - Number of attacks

We get one attack die for each laser rifle. The auto laser receives Sustained Fire which gives us 3 attack dice. 

Step 3 - Roll to hit

As the rebels are skulking in some bushes they are in Light Cover which is the only hit modifier. This means our Shooting Skill is modified down to a 2, so we have to roll a 1 or 2 on 1D6 to hit.

Rolling the dice for the rifles we get a 1, 2, 4, 5 so 2 hits. The Auto Laser rolls a 1, 5, 6 so 1 hit. If we had rolled a pair of 6s the gun would also have jammed. 

Step 4 - Roll for damage

This is quick. Since the Impact of the rifles is the same as the Defense score (3 in both cases) a roll of 1-3 will inflict damage. We had 2 hits so I roll and get a 2 and a 3. Both hits inflict damage.

The Auto laser has a higher Impact value (4) so a 1-4 inflicts damage. A 3 means it is another damaging hit. 

Not that it does not matter how much higher the Impact is. It is always a 1-4.

Step 5 - Armour

The basic roll required is equal or below the Armour rating (a 2) to deflect the hit, but laser rifles have an AP rating of 1, meaning the Armour rating is reduced by 1. The dice come up 1 and 5 so one hit is deflected and the other is a casualty.

The Auto laser has an AP of 2 so it blows right through the Armour. 

Step 6 - Remove casualties

Easy enough here. The two targets closest to the attacker are removed as casualties. 

Step 7 - Test Morale

At the end of the Fire Combat Phase the rebels will have to test Morale since they lost a figure. This is a 2D6 roll with a roll equal or below the Leader Skill of the squad. 

Since we are not within 8" of the target, they become Pinned if they fail. If they had enemies within 8" they would instead Break on a failed test.

And that is it

It looks like a lot of steps when you break it down but each only takes a few seconds to carry out.