Hammer of Math: Leman Russ Turret Mayhem

This week’s Hammer of Math dives into the realm of really big guns and the tanks that drive them, focusing on the main weapon options of the Astra Militarum Leman Russ Tank.

The Astra Militarum are defined by two key elements; hordes of unfortunate humans getting slaughtered and giant metal boxes with turrets on top making everyone around them prematurely deaf through superior firepower. The iconic metal box in this case being the Leman Russ Battle Tank, a well armed and armored treaded vehicle that every Regiment loves and more than a few practically consider Troops. As befitting a key vehicle with years of lore and rules development, the Leman Russ has a considerable number of variants and options. If the traditional battle cannon doesn’t suit a player, they can consider a massive plasma gun or even a tank-scale sniper rifle. As one might expect the viability of these weapons changes considerably from codex to codex, and the latest release of Codex: Astra Militarum is no different.

Valhallan Leman Russ. Credit: SRM

Turret Weapons

While the BS of a Leman Russ still hasn’t changed (4+ for everyone), Leman Russes lost Grinding Advance (shoot twice when moving under half) in exchange for Turret Weapon. Turret weapon provides two benefits. First, the tank adds 1 to hit rolls. Second, the tank can no longer be shut down by being mobbed by a bunch of throwaway infantry. Now the tank can still fire at units that are outside of its Engagement Range while in combat, but at a -1 penalty. Going from a 4+ to a 3+ on regular shoting immediately improves the tank’s offensive output by 33%. Many of the weapons have also received a significant improvement in the number of attacks, going away from the standard D6 shots that most weapons had from before.

Leman Russ Executioner. Credit: Rockfish
Leman Russ Executioner. Credit: Rockfish

Weapon Comparison

Here are the various options available to a Leman Russ. When compared to previous versions I do my best to make the comparison as general as possible, but if a particular stat is required (such as a save due to an AP change) I will specify it in the description. The comparison being made is expected wounds; the amount of damage expected to be delivered to a target on average. The general comparison will be between a tank from the previous codex firing via Grinding Advance versus firing once with the benefits of Turret Weapon.

  • The iconic weapon for the Leman Russ Tank is creatively named the Leman Russ battle cannon, and there are two changes to this gun. First, the attack profile has changed from D6 to D6+3. Second, the damage has changed from D3 to a flat 3, which is a considerable improvement both in terms of raw improvement and variability. Relative to the old version firing twice the new iteration has 186% the output, despite never being able to achieve the full 12 shots of the old gun.
  • The demolisher battle cannon, a short ranged (24″) S10, AP-3 D3+3 weapon with Blast. Historically the demolisher was a terrifying short-ranged monstrosity, with Space Marine Vindicators able to wipe out vast swaths of enemies with their 5″ pie plates of doom. Its current state remains shameful. Relative to the last codex the only difference is that the damage is D3+3 instead of D6, which (along with the +1 to hit modifier) makes the new profile 190% as effective.
  • The eradicator nova cannon is theoretically a Marine killer, with a respectable 36″ range and D3+6 S6, AP -2, D2 shots with Blast and the ability to ignore Light Cover which is always nice. Relative to the old version this one gets more shots and has no variable damage. That makes it 171% as effective.
  • The executioner plasma cannon is power creep personified. Featuring a D6+3 shot profile at S7, AP -4, and D2 with the option to overcharge to get to S8 and D3, on average this weapon gets twice as many shots with more AP and damage than the previous iteration. To put that into context against a targets with a 3+ save the expected damage of the new version is 223% that of the same weapon before.
  • The Exterminator received a considerable improvement and is now a bona-fide T4 killer thanks to its S8, AP -2, D2 profile with 6 shots. The new version has 2 more shots, 1 more strength, and 1 more AP which is just unpleasant. Against a T4/3+ profile that gives the revised weapon 167% the output of the old one even with fewer shots under Grinding Advance.
  • The punisher gatling cannon is the answer to the question “what happens if we accidentally let an Ork design a tank gun”? This Heavy 20, S6, AP -1 D1 monstrosity is clearly designed to annihilate hordes of lightly armored enemies, but what’s interesting is that relative to the original version the only changes were an increase in the Strength characteristic and AP. This means that the number of attacks is unchanged, making this weapon effectively get half as many shots compared to the old version with Grinding Advance. I guess the expectation is that with a 24″ range you’re likely going to be moving anyway. If the attacker is stationary then against a T3/5+ target like a Gaunt the improvements to hitting, wounding, and reduced save make the new punisher 104% as effective as the old one. Anything tougher and it’s a significant decrease.
  • The vanquisher battle cannon was a bit of a disappointment previously, but the new one appears to have redeemed itself. The single attack hits at S14 with an AP of -5 and D3+6 damage, but it also ignores invulnerable saves AND inflicts an additional D3 mortal wounds if the target is wounded by the attack. The level of improvement here is absurd; against a T8/5++ target like a Knight you’re looking at 333% the expected wounds of the previous iteration. Meanwhile the Repulsor Executioner still sucks.

Example Output

Probably the best way to see how the various weapons work is to put them against different targets. For this analysis we’ll assume no regimental doctrine or orders, although the default of Born Soldiers will increase the output (particularly for lower strength weapons). We’ll start with a T8/3+/5++ profile which can represent a wide variety of targets, which is shown in the chart below. Note how the median value for the vanquisher battle cannon was actually 0; while the vanquisher has a very high floor when it hits the combination of having to hit and wound on 3+ means that the net probability of hitting and wounding is only 44%. This is definitely an example of where Gunners, Kill on Sight! or the Veteran Commandeer (yes, that’s how it’s spelled) Tank Ace option with Elite Sharpshooters would be useful. The demolisher is also particularly interesting thanks to the combination of large number of shots, high strength, and high damage potential.

Next up we’ll look at something a little more vulnerable; a T5 target with a 4+ and 3 wounds like a Tyranid Warrior. I assumed that a unit of 6 was the target to examine the impact of the first level of Blast. Unsurprisingly the Executioner is extremely useful here, with a damage characteristic of 3 allowing it to melt a Tyranid Warrior with every shot. Notably the demolisher and Leman Russ battle cannons also perform pretty well, which is interesting given the high median damage that the demolisher inflicted on the Knight target above.

Finally we can take a look at what it would take to clear out a horde threat like a T3/5+ gaunt. For this we’ll assume that the target is large enough to guarantee the maximum number of attacks for Blast weapons. Here we finally see the punisher in its element, mowing down a median of 9 models and easily outscoring anything else. Second are the three weapons with 9 shots; the eradicator, executioner, and Leman Russ cannons. Behind that is the sadly underperforming exterminator overlapped with the demolisher, and finally the vanquisher brings up the back with a median of 2 dead gaunts courtesy of the mortal wounds.


Leman Russ, Traitor Guard
Leman Russ, Traitor Guard, Credit: RichyP

Wrapping Up

While there are plenty of options available for Leman Russ Tanks there are some clear winners and losers. On the bottom of the pile is the exterminator autocannon, which simply doesn’t have the damage output or number of shots to compete with other options. At the top are the demolisher battle cannon, the Leman Russ battle cannon, and the plasma exterminator. It’s reassuring that the go-to weapon for the Astra Militarum remains a viable option against nearly any threat. For this interested in hitting the big targets, the vanquisher battle cannon has a high floor so long as you take steps to ensure it hits.

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