Tuesday, June 4, 2013

Railgun vs Ion Cannon

"The railgun is dead... and we have killed him" (Friedrich Nietzsche).

Okay, I may have modified the phrase slightly (and we all know Nietzsche played Chaos).  But an overused quote from a dead philosopher is always an acceptable opening to an article.
He has absolutely nothing to do
with this article, but my god look
at that magnificent mustache

The quote's dubious origin doesn't make it less true, though - railguns in the Tau arsenal are much less potent, despite the Hammerhead's version being unchanged in the new codex.

Hammerheads and their traditional railgun armament have always been a staple of the Tau army in past editions for a few reasons.  Their high armor value (for a skimmer) makes them very durable, and the railgun's is capable of bringing down heavy vehicles with its S10 AP1 shot or cutting through infantry with the S6 AP4 submunition's large blast.

None of this has changed in the 6th edition Tau codex.  While the loss of multi-trackers and the new disruption pod rules are detrimental to the Hammerhead, the drop in points cost more than makes up for these losses.  Being an inexpensive, durable, long-range vehicle with flexible firing options makes the vehicle a very attractive choice that fits into pretty much any Tau composition.

I'd like to stress here that I am not arguing railgun-armed Hammerheads are weak.  Everything listed above is absolutely true.  However, the railgun is eclipsed in every important way by the ion cannon because of the role a Hammerhead fills in a Tau army, and we'll go into that argument now.

Let's take a detailed look at how a railgun compares to an ion cannon:

Railguns offer 1 shot at S10 AP1, or a large blast at S6AP4.  Ion cannons offer 3 shots at S7 AP3, or a large blast at S8 AP3, with a chance of overheat.

The two important questions to ask here are 1) What does a railgun kill better, and 2) What should we be shooting with our Hammerhead?  Obviously the choice of weapon modifies question two, but bear with me for a moment.

More functional, though not nearly as stylish
S10 AP1 makes the railgun better at killing any AV 13 or 14 vehicle, granted; at AV 12, the multiple shots from the ion cannon more or less balances it out - the railgun is still better, but the difference is small enough to ignore.  The AP1 of a railgun also makes it more effective against anything with a 2+ armor save.

The ion cannon is better at killing everything else in the game.

That isn't a fair statement to leave on its own, granted - you do need something in your army to deal with heavy targets, and the railgun provides it.  But this is where our second question comes in - of those targets the railgun is more effective at killing, should you be firing the Hammerhead at them?  A single S10 AP1 shot is not a reliable way of bringing down a landraider, since it's reasonable to assume that a competent opponent will have given it some kind of cover or invulnerable save.  Even if the shot hits and gets through, you need a 5+ to penetrate, and a 4+ to destroy.  So, if we assume a 5+ cover save, you have a 2/3 * 2/3 * 1/3 * 1/2 = 2/27 chance of killing a land raider per railgun shot.

Goodnight, sweet prince
Things are even worse against models with 2+ armor.  Small targets like terminators are a terrible waste - you would most likely do more damage with a submunition than a solid shot against a unit with 2+ saves, so we'll leave them out of any calculations.  This leaves us with monstrous creatures, very few of whom have 2+ saves -  non-winged Hive Tyrants and Riptides being the notable exceptions.  The tyrant is just going to take the hits on his Tyrant Guard or shrug it off with FnP, making the railgun not particularly effective.  Riptides are unfortunately so durable (or not, you are playing Tau) that railguns are an enormous waste here as well.  Even if we assume the Riptide doesn't have FnP or is generating a 3++ save, a railgun shot has a 2/3 * 5/6 *2/3 = 10/27 chance of inflicting a wound.  You'd need three hammerheads firing for five turns uninterrupted to bring down just one Riptide.

Simply put, railguns are an enormously ineffective way of dealing with heavy targets because despite the weapons power, it's just one shot.  If you want to bring down heavy vehicles, you should be using fusion blasters, riptides in combat, or even EMP grenades - all of these are readily available to a Tau army, and are much more cost-effective ways of taking down vehicles.  Against monstrous creatures you'll find massed S5 firepower, plasma, fusion, or ion-accelerators are enormously cost-effective solutions than a Hammerhead.

To be fair, the numbers I list above could be easily modified via markerlights, boosting BS and negating cover to give the railgun a more reasonable damage output.  But consider that those markerlights could be spent just as easily on one of the alternative units listed above, and to much greater effect - why spend three markerlight points on a single Hammerhead when you could do the same for four Piranha?

Terran has been waiting 15 years
for this rules update

Compare this to the ion cannon.  Granted, 3 shots at S7 AP3 isn't overwhelming, but it's a solid choice against monstrous creatures, transports, and any single model with a 3+ save.  Most of the time, though, you're using the ion cannon for that beautiful S8 AP3 template.  Unlike the railgun submition, an overcharged ion shot is a threat against anything with a 3+ save and causes Instant Death against T4 models, making it especially effective against multi-wound units and infantry with FnP.

So in summary, the ion cannon is superior to the railgun because it lets your Hammerhead's do its job more effectively.  Most of the Hammerhead's power comes from its template, where ion has a clear advantage.  And while the railgun may be more useful against certain targets, it's important to understand that these are not the targets a Hammerhead is good at killing in the first place.

Leave other units to deal with the land raiders and riptides, and let your ion cannon do what it does best - killing everything else.


  1. I would have to say I agree, I just can't think of a use for a railhead anymore.

    It is also a shame broadsides seem to be switching over to HYMDs now as the Tau have lost one of their most iconic weapons.

    I guess I may still build one into my army just for the legacy and fear factor.

  2. But what do you use then against high AV vehicles?

  3. Fusion blasters are the most available option. Riptides and piranhas are both very fast and not too difficult to get into position for 2d6 penetration, and stealth or crisis teams can also do the job pretty well, especially with infiltrate, outflank or deepstrike. EMP on fire warriors is a decent option too, though mostly against high-armor walkers or transports.

  4. I love your blog, and endeavor to read it whenever possible, but I think there are three major omissions which may make the Railgun slightly more attractive.

    1. Longstrike. He pairs better with the railgun for heavy tank killing, than with the ion cannon for large blasts. If you think he is worth it... =P But, pushing 1750pt games you might need to spend more points on HS, and you want it to be something effective, and if you chose to run longstrike in this situation - you want him to have a railgun.

    Yes, in 1500pt games or less you won't have the same restrictions on slot availability. Its really only applicable for 1750 pt games +

    2. Barracudas. They have the same weapon loadout with the ion cannon (and MORE!), which may make the railgun preferable due to the rarity of s10 ap1 weapons. I could seriously imagine myself running a list with 2 - 3 barracudas, and do we REALLY need more S8 AP3 large blasts? =P. Popping those tanks with railguns may be more beneficial, especially as those juicy space marines may be waiting inside for large blast fodder...

    3. Mathhammer for Vehicular Death. ASSUMING Railhead = Ionhead in cost (yes, this gives the railhead a 4% advantage which I will acknowledge here, but it saves A LOT of decimal points)
    Formulae -
    Hit Chance - Number of Shots x Chance to hit
    So the Railgun shoots 1 shot TIMES a 4/6 chance to hit = 66.67%
    Glance Chance - Hit chance x chance to glance +
    So the Railgun has a hit chance of 4/6 TIMES 6/6 (if against AV10, as all results would cause AT LEAST a glance), so hence the answer is 66.67%
    Pen Chance - Hit chance x chance to pen
    Same logic as above
    Boom Chance - Pen chance x 1/6 (3/6 for Railgun, as AP1)

    RAILHEAD (R) hit chance = 0.67. IONHEAD (I) hit chance = 2.00
    AV10 - (R) Glance Chance 66.67%
    Pen Chance 66.67%
    Boom Chance 33.33%
    (I) Glance Chance 133.00% (so 1.33 glances predicted)
    Pen Chance 100.00%
    Boom Chance 16.67%
    AV11 - (R) Glance Chance 66.67%
    Pen Chance 55.56%
    Boom Chance 27.78%
    (I) Glance Chance 100.00%
    Pen Chance 66.67%
    Boom Chance 11.11%
    AV12 - (R) Glance Chance 55.56%
    Pen Chance 44.44%
    Boom Chance 22.22%
    (I) Glance Chance 66.67%
    Pen Chance 33.33%
    Boom Chance 5.55%
    AV13 - (R) Glance Chance 44.44%
    Pen Chance 33.33%
    Boom Chance 16.66%
    (I) Glance Chance 33.33%
    Pen Chance 00.00%
    Boom Chance 00.00%
    AV14 - (R) Glance Chance 33.33%
    Pen Chance 22.22%
    Boom Chance 11.11%
    (I) Glance Chance 00.00%
    Pen Chance 00.00%
    Boom Chance 00.00%

    Note, these stats do not factor in cover or saves, and is a failure of my mathhammer.

    I would argue that the more shots from the ion cannon does not balance with the railheads strength. Even going back to AV 11 a railhead may beat the ionhead. For Medium to Heavy tanks, you want the railgun, period. And spare markerlights would help the railgun in these regards more than they would help the ion cannon.

    And I haven't gone in to coupling tank killing with longstrike. A lot of those railgun pen chances get a VERY big bump =)

    Nonetheless, very very nice read. I look forward to more.
    I might write one myself about Fireblade vs Ethereal, if i get the time =)

  5. Barracudas sound solid, but I haven't looked at them. Very few tournaments in my area allow forgeworld, so I tend to ignore fw rules for any comparisons I'm doing.

    And I agree, no question that railguns are superior tank hunters to ion cannons. They more or less break even at AV11, and even then the railgun is preferable. The point I wanted to make with the article is that hammerheads are unreliable at killing heavy tanks with either weapon set; granted, Longstrike helps, but his points cost is dubiously high. If you need to kill AV13 and 14 vehicles, riptides or piranha are much more reliable options. You sacrifice range, of course, but I'd prefer a high chance of taking down a land raider turn 2 than a slight chance on turn one.

    So if you want anti-tank, there are better options than a hammerhead - take those instead. And if you want to kill monstrous creatures, marines, large units, or almost anything else, the ion cannon is much more effective than the railgun. Basically, the railgun only wins out if you're using your hammerhead for a role it doesn't fill particularly well anyway (compared to models with fusion blasters, I mean).

  6. "Basically, the railgun only wins out if you're using your hammerhead for a role it doesn't fill particularly well anyway (compared to models with fusion blasters, I mean)."

    Thank you for the reply. I'm going to ponder this point with the codex handy. To be personal, I have had much success with deep striking twin linked fusion, and may continue to use this.

    I'm going to keep fielding Ion Cannons for now, but may revisit the humble railhead IF I ever field barracudas.

  7. Piranhas? Really? They are BS 3 for crying out loud, and if you don't take the expensive Disruption Pod (thats 45 points for 3), they will drop like flies before they even reach the tank(s) they want to fry. And even when they do, it's a 50/50 chance before you even get the chance for rolling armor pen