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Warhammer 40K, The Myth of Codex Grav: Against vehicles

There's always talk about how overpowered grav-guns are compared to other special weapons.

At a glance, they're right. Good range, a ridiculous number of shots per weapon, no overheating... And the heavy version pack the amplifier meaning they get to re-roll wounds on top of it. You pay a premium for that much beard on a single model, but it's generally worth it.


I want to show you now it's not the auto-take you may think it is, and that you must use finesse in deployment. Hopefully at the end of this you'll consider when to use them more carefully. They are potent, no doubt about that, but they are not a magic "I win" button.

I originally started thinking about this when I was equipping the school's flagship Marine army. It's a drop pod and Rhino duo, with one bit of extra flavour, and I wondered if a Grav-canon in place of a melta-gun. Turns out it might not be worth it, but it prompted this analysis.

We'll be looking at their effectiveness versus vehicles first, to show that every weapon has their place, and it is where grav-weaponry is at it's "weakest".

Let's do some maths!

Points Range Shots Hits 10 11 12 13 14 Average
Grav canon 35 12 3 2.00 0.61 0.61 0.61 0.61 0.61 0.61
Grav gun 15 9 2 1.33 0.22 0.22 0.22 0.22 0.22 0.22
Melta gun 10 12 1 0.67 0.56 0.44 0.33 0.22 0.11 0.33
Melta gun 10 6 1 0.67 0.67 0.65 0.61 0.48 0.30 0.54
Relentless Grav canon 35 24 5 3.33 1.02 1.02 1.02 1.02 1.02 1.02
Grav gun 15 18 3 2.00 0.33 0.33 0.33 0.33 0.33 0.33
Multimelta 10 24 1 0.67 0.56 0.44 0.33 0.22 0.11 0.33
Multimelta 10 12 1 0.67 0.67 0.65 0.61 0.48 0.30 0.54

Now the above is a table based on armour values rather than Toughness, because I want to illustrate that they are not generalist weapons.

As you can see, the weapons only grav-canon only slightly about performs the melta-gun when on the move. The grav-gun itself is rubbish, and actually well suited as a specialist weapon for a role which becomes apparent later.

On the surface, the grav-canon seems to be a natural choice, and worth the cost. Well is it? First we need to take into account effective range. For that we just take the average wounds of the weapons and multiply it by the range. We're basically saying longer range is better, and this gives us a nice easy way to quantify that.

After that, we divide the points cost of the weapon by the range adjusted "value" of the weapon. From that we get the below table. Remember that we want high Range Value, and low points to value for efficiency:

Range Value Points/ Value
Grav canon 7.33 7.81
Grav gun 2.00 33.75
Melta gun 4.00 7.50
Melta gun 3.24 5.70
Relentless Grav canon 24.44 1.41
Grav gun 6.00 7.50
Multimelta 8.00 3.75
Multimelta 6.49 2.85

So now we can see that melta-guns actually start to overtake grav-guns on the move, or on a deepstrike. Grav-guns only start to equal the humble melta once they're on a Relentless platform. So grav-bikers are still a good idea.

What you should be noticing is the shocking value of grav-guns on regular marines. They are simply not worth it. The grav-canon is somewhat justifiable, but you have to be willing to pay a premium for each tactical squad. Put it this way, you could afford another tactical squad for the price of two grav-canons.

Multi-meltas are a steal at 10 points a pop, provided you can get Relentless on your infantry.

Now this is not the whole story, and this is where grav guns are weakest. Next time we'l loom at where they shine: Monstrous Creatures and high toughness.

Thanks for reading.

If you liked what you saw, and you want to help out, please visit and donate at my Patreon. Every Little helps!


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