30 January 2019

Improved Calculation of Armour Penetration in the game

We are continuing to develop and improve our approach to shell configuration. When working through the various phases of configuring the shells, we have based those on sources from their countries of origin as well as unified sources which provide data for multiple shells represented in the game, we decided to configure shells on the basis of formulas, which is, in our opinion, the best method for players to easily understand.

This method will make it possible to standardise the armour penetration system and avoid situations where documents from various countries provide different data on armour penetration for the same shell. It will allow us to configure shells much more effectively, yet no less realistically, even when certain data is unavailable.

We are constantly improving the armour penetration system in War Thunder, and right now, we can highlight two phases that have been expressed in its development, each of which is fair and correct in its own way.

The first phase involved the configuration of penetration based on data from documents and firing data for each weapon and type of ammunition. In this case, we prioritised sources from the countries of origin.

The second phase involved the switch to a “unified” system, the basis for which was numerical data from one source per country. This version allowed us, to a certain extent, to collate data from various sources and countries.

However, these phases were not able to unify the armour penetration system and make it comprehensible to players while preserving its documentary and technical basis. These configuration methods also facilitate a peculiar kind of “tug of war” in which various sources appear one after another, frequently with contradictory data. After performing a lengthy and detailed analysis, we decided to improve the current system and make it easier to understand. This is an important step in the never-ending process of improving ballistics and damage models.

You can find out more about shells and armour penetration in the War Thunder Wiki.

The DeMarr and Lanz-Odermatt Formulas

There have been some recent changes that you may have already noticed in the game. These include refinements to the ballistics parameters for high-calibre armour-piercing rounds. In order to do this, we used firing tables and other documents that allowed us to more accurately set falling speeds at range for these shells. For types of ammo for which there was, for whatever reason, no precise data, we used the parameters of shells from the tables with a similar design and characteristics. Having obtained more exact data on speed, we can reevaluate the penetration system using a formula-based calculation. We decided to use the DeMarr formula because it is the most accessible and comprehensible formula for high-calibre armour-piercing (AP/APC/APBC/APCBC) and sub-calibre (APCR/HVAP) shells. When it comes to sub-calibre fin-stabilised shells, we decided to use the Lanz-Odermatt formula. We are still working on APDS shells. Information about them will appear a bit later than the aforementioned ammo types.

One of the new features in the system for calculating armour penetration is that it will now take it into account if a shell contains a chamber full of explosives. The percentage of explosives contained within the shell will be factored into armour penetration indicators – the higher the ratio of explosives to the weight of the shell, the lower the armour penetration. This allows for the more accurate implementation of indicators for semi-armour-piercing and armour-piercing shells with a large quantity of explosives and a relatively slender body.

The implementation of this system for calculating armour penetration will occur in phases: we are planning to start by switching the more commonly-used ammo types. such as high-calibre armour-piercing and armour-piercing fin-stabilised shells, to this system. Then we’ll move on to sub-calibre shells (APCR/HVAP) and sub-calibre shells with a discarding sabot (APDS). There are certain challenges involved in calculating the latter, and it is possible that, for a certain portion of shells, the old armour penetration system will be preserved. These shells represent an insignificant portion of the shells available in game. One example would be the L15A3/A5, M728.

So how will this improve the game?

It will allow us to optimise the penetration system and unify it for all high-calibre (APCR/HVAP) shells. At the same time, it will allow us to avoid situations in which data from various sources and countries is contradictory, since these sources were managed by various systems and penetration methodologies. We believe that the new system will be more transparent and easier for players to understand without sacrificing realism (as an example, in the USSR’s firing tables the data on penetration follows the same DeMarr formula, as do the calculations in AaG). Yet another advantage will be the ability to immediately get penetration data for any high-calibre or sub-calibre (APCR/HVAP) armour-piercing shell for which there is information about its muzzle velocity, falling speed, and mass. For AP/APC/APBC/APCBC shells we have also recalculated the effect of incline – the effect whereby the thickness of the armour being penetrated drops as the incline increases (the slope effect) when performing formula-based calculations in order to achieve uniformity and eliminate certain inaccuracies in their current values. As you can see from the examples below, compared to the current values for an angle of incidence of 30 degrees, penetration ends up increasing, and for an angle of 60 degrees, on the contrary, it drops. According to our evaluations, the role of proper tank positioning, i.e. placing the tank correctly in relation to the weapon being fired, will increase. Using this chart you can familiarise yourself with the formula for calculating the slope effect for AP/APBC/APCBC shells and the resulting slope effect values.

APCR/HVAP and APDS shells will get updated slope effects that will make it possible to more accurately factor in the technical characteristics of a shell’s construction that influence the penetration process. For APCR/HVAP shells the indicators for speed reduction will be ascertained based on the example of how this was done for APHE and APDS shells.  The new system is so simple and productive that, if you know a shell’s individual attributes, you can calculate its penetration using the DeMarr formula on your own.


Foreseeing questions about “historical accuracy” and correspondence with actual firing data, we should mention that the data used to calculate armour penetration figures are based on existing documents and is nothing out of the ordinary. Historical and technical accuracy will remain one of the key parts of the game, but the game environment cannot match reality exactly, so the values used for our calculations allow for a certain degree of conventionality.

The War Thunder Team

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