Hammerhead Gunship
The TX7 Hammerhead Gunship is the Tau's analogue to a tank. Like(almost) every vehicle in the T'au arsenal, it has a distinctly piscine name. It can mount either a railgun or an ion cannon as its primary weapon. Both have two firing modes: one against hordes of infantry while the other works better against tougher targets. Forge World used to make some additional primary weapon options for the Hammerhead: two long-barrelled burst cannons, twin-linked missile pods, two plasma cannons, or two fusion cannons. Unfortunately those parts are no longer in production, so you better get busy converting some of your own if you want them. Rules for these systems can be found in the Imperial Armour Index: Xenos.
Secondarily it is equipped with either a pair of independently targeting gun drones, a twin-linked pair of burst cannons, or a twin-linked smart missile system. The gun drones' advantage is that their guns count as being the Hammerhead's as long as they are embarked, making their weapons a lot more reliable and don't suffer from the -1 To Hit if the Hammerhead moves as they are Assault weapons. Don't forget that they have two Pulse Carbines, giving the pair a total of 4x2 shots. The Burst Cannons have the exact same stats, but they cannot be detached and added to a unit to give them two abalative wounds. Smart Missile Systems meanwhile are double the firepower and nearly double the range with the same stats, but at the cost of costing twice as much and being Heavy weapons. Most of the time though these secondary weapons are moot points unless there's an emergency, since the Hammerhead will usually try to stay outside ranges at which it needs to use them anyway, so most people take drones and detach them to press forward or create cover and distraction targets while Hammerhead stays on the back lines.
Fluff says that it and the Leman Russ tank are more or less equally matched. Given the number of Leman Russes in existence compared to the number of Hammerheads, though... probably sucks to be a Hammerhead in the fluff. On the other hand, in the Taros Campaign the Imperial Guard lost five to six Russes for every Hammerhead destroyed, though considering they were waging war in the flat, open desert with no cover, under constant markerlight-guided missile barrage, and with supply lines being cut almost the second they were established, those statistics may be misleading. However, if you are to believe what Dawn Of War and its expansions demonstrates (which is debatable in and of itself), the Hammerhead is vastly superior. To be fair though, the T'au needed BIG units, and the Hammerhead probably fit really nicely into that slot. In short, no one really knows which tank is better, though it tends to lean towards the Hammerhead.
Unlike the Leman Russ, the Hammerhead is not intended to smash its way into enemy lines, instead hanging back and exploiting the 72" range of the railgun to put holes in the Tau's enemies while taunting them to try and rush it. If this is the case, then the Vanilla Hammerhead could be said to be more closely related to a Tank Hunter than a true tank.
In 4th and 5th Editions, the Hammerhead competed with Broadside Battlesuits for heavy support slots. For roughly the same cost, a trio of Broadsides could put three twin-linked railgun shots on target compared to the single-shot Hammerhead. However, the Hammerhead could move further before shooting, and could fire the S6, AP4 large blast template to vaporize light infantry, while Broadsides could only, at best, bump off three soldiers with a lucky round of shooting. For the 6th Edition Codex, Games Workshop decided to "resolve" the conflict (read: give people a reason to spend their money on both Broadsides and Hammerheads) by changing the Broadside's main weapon to the "heavy rail rifle"—nerfed to S8, but with the option of getting Skyfire, making them a threat to flyers in a way that a lone Hammerhead never could be. Although admittedly this nerfing makes sense fluff-wise since the Hammerhead's railgun was always larger than a Broadside Battlesuit's.
Comparison to the Leman Russ
"Shas'ui, I have spotted the Gue'la tanks sitting on the horizon line, twelve kilometers downrange! Engaging now!"
- Three seconds later* CLANG, KA-BOOM! The Leman Russ spontaneously explodes
Much like a cold war tank, the Hammerhead is low to the ground with good (if the model is any indication) gun depression (said to be from -10° to +28°), with a main gun that can be either anti-tank or anti-infantry depending on its firing mode, while being blisteringly fast. Further, its role is more akin to a U.S. tank than a Soviet one, as western tanks were built to take on lots and lots of Soviet tanks at once. As mentioned, Hammerheads are almost always drastically outnumbered by Leman Russes. (Who are the communists supposed to be here, again?)
Tactically they fill the same niche as a modern tank, an element supporting mechanized infantry advancing very, very quickly, and taking out armor while using its machine guns on infantry, and The ion cannon fills a role similar to a Bradley's chain gun by taking out infantry and (if a modern military ever faced power armor) heavy infantry. While it does have rather fine armor, Hammerhead rely more on evasive maneuvers, disruption pods and straight up outranging it's opponents to survive, so it can potentially withstand twice to trice more anti-tank fire than most imperial tanks. The Leman Russ, on the other hand, is a World War II tank and it shows; it's much slower and has a much broader silhouette, but it's bristling with guns and relying purely on it's thick armor, while lacking more sophisticated defense systems.
On the Tabletop
The Hammerhead carries a decent profile: T7 W13 3+ means it can take a beating, while its BS3+ lets it fire its weapons reliably even when utilizing its 12" Fly movement. It does degrade over time at 6 and 3 wounds: each time its movement halves and its BS becomes 1 worse, and its attacks degrade like every other tank. A basic Hammerhead clocks in at 133 with two drones. You then have to pick either a Railgun or an Ion Cannon:
- The Railgun is the cheaper and better option of the two and nets you either a 72" Heavy 1 S10 AP-4 DD6 shot that deals an additional D3 Mortal Wounds on a 6 To Wound, of a 72" Heavy D6 S6 AP-1 D1 shot that can put a dent in hordes. This is the inferior option however: the massive amount of Burst Cannons and Pulse weapons mean that you've got plenty of options to deal with everything below MEQ.
- The Ion Cannon gives you a choice as well: either a 60" Heavy 3 S7 AP-2 D2 shot or a 60" Heavy D3 S7 AP-2 D3 shot that goes up to Heavy D6 against units 10+ models in size, but causes a Mortal Wound for every 1 you roll To Hit. Generally the Ion Cannon is not really worth it: you have better guns to deal with TEQs and the overcharge shot is only the superior option when dealing with large units, which rarely warrant the D3 anwyay.
Then there are the support weapons. Two gun drones at 16 points is a nice deal, granting you 8 extra shots at close range to deal with light infantry. Not only that you can detach them near an Infantry or Battlesuit unit to give them two extra wounds, which is immensely helpful with your more expensive units. For 20 points you can instead take two Burst Cannons, but those have the same firepower as the drones do and can't detach. The Smart Missile Systems are expensive at 20 each, but ignore cover bonuses and can be fired blind at the cost of being Heavy weapons, but this is offset by the Hammerhead's BS3+ and high rate of fire. Finally it can take up to two Seeker Missiles at 5 points each, which are always welcome.
The Forge World versions suffer from being massively overpriced. Their primary problem is that the hull itself already clocks in at 161 points, and it doesn't even have guns at that point. If you want to make a powerful missile boat out of the Heavy Bombardment Hammerhead with its standard High Yield Missile Pods, two Smart Missile Systems and two Seeker Missiles you're looking at almost 300 points. And the 8 S7 AP-1 DD3 and 8 S5 AP0 D1 shots just are not worth it. Even going with the cheapest option you're looking at a tank that's 100 points more exensive than the Railgun Hammerhead. The Fire Support Hammerhead is 171 bare and requires some very expensive weapons:
- The Twin Fusion Cannon is the cheapest at 54 points. They're a pair of Fusion Blasters with 24" range delivering a Heavy 2 shot and nets a reroll of the damage within half range. On paper it's better at popping tanks than the Railgun and utilizes the tank's speed and Fly ability to get close, but afterwards you'll be a sitting duck, which is pricy for a model that's almost 250 points.
- The Twin T'au Plasma Cannon is a pair of souped-up Plasma Rifles, shooting 4 shots at 48" S7 AP-3 D2. This makes the gun surprisingly effective at taking down TEQs from a distance, but its 60 point price tag makes it five and a half times as expensive as a regular Plasma Rifle.
- The Twin Heavy Burst Cannon is the closest the Tau have to a Leman Russ Punisher. A whopping 16 shots at 36" dealing S6 AP-1 D1 damage, it can tear through entire infantry squads in one turn. The downside is, once again, its cost: 70 points. While it's tempting to give your Hammerhead this weapon and two regular Burst Cannons for some delicious dakka goodness, remember that this will set you back 261 points, which is way too expensive for what it does.
Finally there's the option of taking Longstrike. At the low cost of only 20 points, you'll get BS2+, +1 to wound against Vehicles and Monsters, +1 To Hit for other Hammerheads within 6" and has For the Greater Good, netting you some extra shots in case of a charge. To get the most out of him you'll need at least one additional Hammerhead, but it's worth it for the improved performance.
The Hammerhead's signature railgun is was also carried by the XV88 Broadside Battlesuit, before it was downgraded to a lighter but faster firing Heavy Rail Rifle. If you want pure Rail goodness the Hammerhead is currently the superior option: the Hammerhead is slightly cheaper but far sturdier and can lay down more reliable damage, even when counting the fact it fires more slowly. Overall the Hammerhead is an excellent tank and a mainstay of Tau armies for a good reason.
Power Ratings
With Power Ratings the Hammerheads are slightly behind the 20-points-per-power curve, but still make for excellent tank hunters. Longstrike is still worth it as well, costing 11 power. The real stars are the Forge World configurations: costing the same 10 points as the regular Hammerheads they suddenly become viable. The missile hell of the Heavy Bombardment Hammerhead is suddenly a lot more viable and outclasses the similarly-armed Broadside greatly, while Fire Support Hammerheads become usable as well. The Twin Fusion Cannons might still not be entirely worth it, but the Twin T'au Plasma Cannons become an option and the concentrated fire of the Twin Heavy Burst Cannons let you concentrate your firepower on a single unit.