|Play to Kill|
Today, we're going to talk about the main battle tank of the Tau army, the Hammerhead gunship. Specifically, I'll be breaking down the ion cannon vs. the railgun option I have never run an ionhead, but sixth edition has inspired me to look into more options. Let's take a look at this awe-inspiring tank and how it may find a new niche in Tau.
The main battletank of the Tau Empire offers a mobile, versatile and highly lethal firing platform for a high price tag. I has armor thirteen in the front, twelve on the side and ten in the rear. When outside of twelve inches, the hammerhead has a 3+ cover save with a disruption pod if it moves. With a multitracker it can fire two weapons while moving twelve inches a turn. The hammerhead comes with a targeting array built in, netting it ballistic skill four, and cannot take a second. The ability for the hammerhead to take a blacksun filter allows it to ignore the increasingly frequent night fighting of the 41st millenium. The hammerhead can do it all in style.
Most hammerheads are usually 'railheads' because the railgun was the weapon option of choice for Tau cadres. The railgun brings both the solid shot just like the broadside, but also provides Tau their primary blast weapon a strength six armor penetration four large blast. This was Tau's best answer to either mass medium infantry or gants with Feel No Pain while offering the strength ten solid shot. This versatility was very powerful and still is, though without a target lock the hammerhead can become an anti-infantry gunship with the option to fight other tanks rather than being a tank designed to fight other tanks (e.g. lascannon predators). In fifth edition, there was little argument for the ion cannon turret, but now there may be more.
|I'll be keeping an ion you!|
TL;DR: The ion cannon isn't as bad as it looks.
Let's start with shooting at vehicles. To calculate which is better we need to consider the expected value of each round of shooting. The railgun's expected value is the same as it's probability as it only has one shot; however the ion cannon's expected value is thrice its probability. So let's compare the probabilities to strip a hull point [P(glance) + P(penetrate)]P(to hit).
Probability Railgun Ion Cannon
vs. AV 10 0.667 1.333
vs. AV 11 0.667 1.000
vs. AV 12 0.556 0.667
vs. AV 13 0.444 0.333
vs. AV 14 0.333 0.000
Looking at the above table you can see that if you are trying to strip hull points off of a vehicle to kill it you should take the ion cannon unless you expect to be fighting leman russ or land raiders en masse. This is with the condition that you should be taking at least one team of broadsides. In some cases you can't afford to wait for the hull point to wear down vehicles.
|Pictured: Target-Rich Environment|
The real difference in performance between the two comes based on the armor save of the target rather than its toughness. Against a tyrannofex the railgun still can expect 0.556 wounds, but the ion cannon's expectation drops to 0.222 wounds. The railgun would have it's output drop against a dreadknight with its 5+ invulnerable save, but it would still outshine the ion cannon by 66.7% (0.370 compared to 0.222).
|Where's the kaboom?|
Now let's consider the Ork nob. Either on foot or mounted, the railgun can inflict instant death, but the ion cannon cannot. Both weapons will be testing against a cover save if the squad can muster one, but let's run the numbers. Against a foot squad, the railgun can either fire a solid shot with 1.111 expected wounds or a blast marker that will wound 0.556 of those it hits if they have cover, 0.833 if they do not. The ion cannon can expect 1.667 wounds against a foot squad and 0.833 against a bike squad. The railgun can expect 1.111 wounds against a foot squad and 0.556 against a bike squad, as its built in cover save effectively negates the instant death property of the railgun. If the cover save were negated by pathfinders, both would double their expected wounds and the ion cannon still wins out.
|Dear Tau: Please go die. Thank you.|
As we saw with the chances to kill a vehicle through hull points, which turret weapon is a better choice for a hammerhead is dependent on what you expect to see in your local tournament setting. If you're expecting medium armor values or marines on foot I'll cover the utility of the secondary weapon in my next post on the skyray, as I did not expect this post to run as long as it did. I apologize if this post was too long, but I hope this has illuminated the complexities of a choice that I had taken for granted for as long as I've played 40k. That's all for the hammerhead, next time I'll take a look into the other staple vehicle of the Tau Empire that was given a hilarious new lease on life.
I'm Underground Heretic and I get to live with that every day!