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Jun 7, 2013

Gun Accuracy in Real Life

By EnsignExpendable

The issue of gun accuracy (let's forget for a moment that when most people say accuracy, they mean precision) comes up a lot when discussing the game. Obviously, since engagement distances are very short, accuracy is reduced compared to real life, or no one would ever miss. In a previous article, I pointed out how the M-30 gets shafted about half as much as the D-25. Let's use some extremely scientific methods to determine the shaftedness ratio (SR) for some guns in the game: the ratio of in-game dispersion to real life dispersion. A high SR corresponds to a gun that is highly nerfed compared to real life.

The Soviets used a metric called average deviation to determine how precise a gun is. Average deviation is given for three axes. Since the game doesn't tell you the length-wise dispersion, let's focus on the horizontal and vertical deviations. A bunch of them are given here.

Comparing average deviation to maximum deviation is a bit hard, but not impossible. Due to the magic of a normal distribution, you can convert between the two. The current system is allegedly off at 3 sigmas (it will be 2.5 in 0.8.6). In a standard normal distribution, the 50% boundary lies at about 0.67 sigmas. Half of your shots should land within the closest 22% of the circle. This may not be true if the distribution isn't standard (we know it's normal, so please no whining about impulse in the comments), but for the purpose of comparing ratios, it doesn't matter that much.

Now, let's take the figures for the guns in the linked article, and figure out how badly they got shafted! I will use the 1000 meter figure to calculate precision, since they are all 0.1 meters at 100 meters, and that's boring. Since real life deviations aren't circular, but in-game ones are, let's use the larger of the values.

NOTE: the values, in most cases, are given to the nearest decimeter. This means that a small change that puts a gun from, say, 0.5 meters to 0.6 meters, has a sizeable effect on the SR.

Starting at the lowest caliber, we have the DShK 12.7 mm machinegun. Just like in the game, the dispersion isn't that stellar, 76 cm. At 100 meters, that's 7.6 cm. The 100% dispersion is 57 cm, and the 50% dispersion, using the 22% rule above, is 12.54 cm. That's a shaftedness ratio of 1.65.

Cranking up the caliber to 20 mm on the TNSh autocannon, we get 7 cm of dispersion at 100 meters, 100% dispersion in-game of 53 cm, 50% dispersion at 11.66 cm, and a shaftedness ratio of 1.66. Pretty consistent so far.

Getting out of the autocannon region, we advance to the American 37 mm M5 gun. Compared to the TNSh, it's a sniper, at 4 cm at 100 meters. In game, the 100% dispersion at 100 meters is 46 cm, 50% dispersion is  10.12 cm, and SR is 2.5. That's pretty nerfed!

Let's see how the German 3.7 cm gun does. 5 cm at 100 meters, with the same 46 cm of 100% dispersion as the American gun. That's the same 10.12 cm of 50% dispersion, and a SR of just over 2.

Moving up in caliber, the British 2-pounder gun (40 mm). The maximum deviation is 4 cm (although the horizontal deviation is an impressive 2 cm) at 100 meters. In game, it's 36 cm for a 100% radius, or 7.92 cm for a 50% radius, for a SR of 1.98.

Next up is the Soviet 45 mm model 1937 gun. Artillery tables give us a radius of 6 cm, either 46 cm in game, which converts to 50% radius of 10.12, and gives an SR of 1.68. Interestingly enough, this is the only gun where APCR scatters less than AP. Firing only gold, the SR goes up to 2.

Sadly, I have no data on 50 mm guns, so let's skip all the way up to the M2 75 mm American gun. The impressive deviation of 3 cm at 100 meters is increased to a not so impressive value of 47 cm at 100 meters, or 10.34 cm for a 50% dispersion, matching other similar tier guns. Since the real life precision was much higher, the M3 Lee scores an SR of 3.44. Yikes.

The T-34's 76 mm F-34 gun doesn't do much better. At the same 3 cm, both the Soviet and Chinese versions carry a 46 cm dispersion. At 10.12 cm for 50%, that's a SR of 3.37. Not as bad as the Lee, I guess, but just barely.

Skipping up to 88 mm, the Tiger II's gun gets some impressive results: 2.6 cm at 100 meters. The in-game stat is also impressive, 34 cm. The 50% dispersion is 7.48 cm, for an SR of 2.87.

Moving up a caliber, we get into artillery territory. The 105 mm German 1918 howitzer gets a dispersion of 4 cm (same as the 2-pounder, with an impressive 2 cm on the smaller axis), or 49 cm in game. That's a 10.78 cm 50% dispersion, and an SR of 2.7.

The 122 mm M-30 howitzer has a dispersion of 6 cm, and 55 cm on its TD version in-game. The 50% radius is 12.1 cm, giving an SR of 2.

The 122 mm D-25 has long been the subject of debate among those who care about truth and justice historical accuracy. The dispersion is approximately 2.4 cm, and 46 cm on both the Soviet and Chinese brothers. That makes for a 10.12 cm 50% radius and a whopping 4.2 SR.

The biggest gun I have data on is the 152 mm ML-20S. Its real life deviation is an impressive 3.2 cm, but in-game, SerB's cruel nerf bat reduced it to 50 cm, or 11 cm for a 50% radius. The SR is 3.43. Hey, not as bad as the IS!

So, what do we see here? The low tier, low accuracy guns aren't penalized that much, or else you wouldn't be able to hit anything. The penalty at tier 1-4 is about 2. Tier 5s have a harsher fate, with the SRs going over 3.

Here is a sorted list, in summary.

Soviet 12.7 mm DShK: 1.65
Soviet 20 mm TNSh: 1.66
Soviet 45 mm: 1.68
British 40 mm 2-pounder: 1.98
Soviet 122 mm M-30: 2
Soviet 45 mm 20K (APCR): 2
German 3.7 cm: 2
American 37 mm: 2.5
German 105 mm 1918: 2.7
German 88L/71: 2.87
Soviet 76 mm F-34: 3.37
Soviet 152 mm ML-20: 3.43
American 75 mm M2: 3.44
Soviet 122 mm D-25T: 4.2

Yes, the bottom 3 guns are Soviet, but so is the top one. That's explained by most of my data being Soviet. If anyone has tables for Western WWII guns, I'd be grateful. Despite the cries of anti-German bias, Germans are clustered solidly in the middle.


  1. In the defence of WG so would I assume those numbers are for controlled conditions like no wind and fixed mounted, then compare the random deviation between where the shells hit the target. An actual tank would have to face not only wind and engine vibrations but also the fact that you have to actually aim the gun and that is not perfectly accurate.

  2. Try finding WWII Gunnery and Ballistics.

    Good book, may give you what you need.

  3. As I have constantly said, WoT accuracy takes into account gun sights, training, and ergometrics. It was never about just pure mechanical accuracy.

    1. Training is affected by your crew training. Having a 100% crew of one nation be worse at shooting than a 100% crew of another nation would be...disagreeable.

      As for gun sights, if the tables didn't take them into account, they wouldn't be very useful on the battlefield, now would they?

    2. One can look at the 8.8 cm KwK 36, and 8.8 cm KwK 43, and see the difference between shots when training and shots on the battlefield. Which allows for a decent amount of error to creep in over whatever the stock figures may be.

    3. Battlefield error is largely due to not knowing the distance to your enemy. On the defensive, when you mapped out the area, the error would be a lot lower.

    4. Are you suggesting that we should get different max crew training levels per nation? As Germans get 120% instead of 100% before going to skills :P ?
      Or we should get different xp leveling thresholds with every nation :) ?

  4. Making a gun barrel that fires straight is well within the capabilities of even a lightly industrialised country.

    What the in game accuracy numbers are compensating for is that aim time would have to (at least) treble at even moderate ranges to be realistic. Firing a gun on a range at a stationary target at a (and this is crucial) KNOWN DISTANCE is a very different kettle of fish to battlefield conditions. This is where rangefinders and ergonomics rear their heads, and that is one area that the Sovs had issues. Accurate guns and sights are trivial. Making them usable on the field is not.

  5. Rangefinding and real life muzzle velocity is taken into account when calculating WoT Accuracy, not simple mechanical dispersion.

  6. now do it for the L7A1/L7A3.

  7. just a couple of questions since i am interrested in this stuf but dont know much about this.

    Am i right in asuming the vertical dispersion is usualy higher then the horizontal one with one off the posble reasons for this that not all shells have the exact same propellant/burn rate thus diffrent velocities? If so, by how much does velocity differes between shots IRL?
    Can i asume ingame acuracy on the move is many times higher then IRL because around WW2 only a few tanks had stabilized gun sights (and eaven if they had, only in one axis i believe)?

    PS: Iam not looking for any bias reason or whatever since i know some ingame values are a huge diffrence from IRL numbers to keep the game playable (turret traverse speeds, rof, reverse speeds,...)

    1. 1. I personally would say yes, but don't take my word for it.

      2. Yes and no. As on the move accuracy isn't as easy to test IRL as there are a huge number of factors. Such as speed, tracking, crew skill, terrain and mechanical factors such as stabilization.
      The game also balances tanks accordingly, with different tanks having different on the move accuracies. With some having better ratios than others, such as the Pershing compared to an artillery.

  8. As was already mentioned, key RL accuracy factor, or better said first round hit probability factor is ranging. Ranging is more important for slower flying projectiles, which travel on more curved trajectory.

    However in WoT, we have 100% ranging in all situations, which favors guns with slower flying projectiles = very strong buff. Therefore, in order to retain their relative performance, you need to nerf them more.

    In game terms - you need to buff russian 152 and 122 mm guns more than german 88.


  9. >The current system is allegedly off at 3 sigmas (it will be 2.5 in 0.8.6)
    It is 1.3 sigmas now and will be 2 in 0.8.6.
    Sorry, dude, this article is completely wrong.

    1. This article was written before the developers came clean with how the system really works. You're right, I should have changed it.

      But, ultimately, it is about ratios. Regardless of how many sigmas there are, a gun with a higher ratio is more nerfed than a gun with a lower ratio. It's in the article, maybe you should read it.

  10. Can only talk about modern guns we shot, the Leo2's 120mm for example can hit a 10cm diameter disc at 2000m with a hit rate of 92%. At least that was my hit rate back in the days. But thats laregy dependant on the gunner, who accuratly he can laser in with the "steering wheel". I hated that thing on the Leo. Anyways, the gun pretty much hits what you aim at .. Always ..

  11. " Despite the cries of anti-German bias, Germans are clustered solidly in the middle."

    Nice straw man.

    Anyone with half a brain knows that we haven't (yet) had the engagement distance in-game to get much if any use out of the difference in accuracy between the various guns

  12. I am very excited about the new 8.10 patch. Lots of new things are coming up. They changed the maps that are prone to CAMPING and now they are also introducing the new lineup for Japanese Tanks. I can't wait to have them tried by myself come new patch! :)

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