Gaijin Calculator overhaul

I believe I’ve seen the source you are mentioning, as I vaguely remember reading a description of the inner workings of an APCR round that talked about how the jacket of the APCR round would impart it’s kinetic energy into the core when penetrating armor, alongside this image.



Personally I don’t think this makes much sense, at least not to the extent that it is represented in the game. The jacket is far wider than the core, so before it can even impart its energy into the core, it has to go through the armor that it is hitting, so a lot of that “additional energy” would be wasted on even trying to reach the core.

My adjusted APCR formula doesn’t use carrier weight. Ignoring carrier weight actually gets it closer to Soviet documents that Conraire shared.


Soviets had some pretty lackluster APCR. So it does seem strange that more advanced HVAP/APCR is bound to the rules of the weaker Soviet counterparts.

I’m pretty convinced the whole calculator system is based on Soviet rounds.


So how would this change to the APCR calculator impact smaller shells like the 30mm PGU-14/B, used by the A-10 / GPU-5/A gunpod?

Info for the PGU-14/B and performance data can be found Here and Here

I’m not sure how the DU penetrator would perform compared to a tungsten carbide core but my suggested calculator gives 148mm at muzzle velocity.

Can you calculate the penetration of the M321(T29E15) HVAP? Same dimensions as M319, with MV of 3775 fps. This projectile is authorized for 76mm guns M1A1, M1A1C, M1A2 and T94.

M321 comes out to 262mm.

M319 comes out to 290mm.

From what I know, DU erodes instead of fracturing and shattering like WC. This decreases flat penetration but improves penetration against angled armor, at least that’s how I understand it working to the best of my ability.

DU APCR rounds like those on the GAU-8 and the LAV-AD’s 25 mm in WarThunder use their own slope modifiers which are superior to those of normal APCR to reflect this. But then they have their own calculator variables, separate from those of normal APCR, specifically to achieve lower penetration values.

I imagine you’d have to make another calculator for DU cores.

Yeah, I knew the two types behave differently. The formula i based my suggestion on is for early tungsten carbide cores. It won’t work for tungsten alloy or DU.

Here’s how the 76mm M1A2 would look with M321 HVAP and T166 APBC. This would be nice for the M4A3 and M18 at 5.7.



Support my suggestion to get these changes implemented.

Regarding the DU core HVAP, current calculation gives pretty much a correct value.

  • PGU-20/U

Penetration data of the PGU-20/U is listed in the NWP 3-22.5-AV8B, Vol. II.
For 2.5 inch RHA at vertical impact, V50 (The velocity at which 50 percent of the projectiles will penetrate the target) is 3368 fps. Current penetration is 66mm at 1036 m/s(3399 fps).

  • PGU-14/B

You can find the penetration graph for PGU-14/B here.
Penetration on 300 BHN plate, at impact velocity of 980 m/s and impact angle of 30 degree, is 73 mm. Current value is 68 mm. It is slightly low but acceptable.

I might work on later stuff another time but I’m focusing on early AP and tungsten carbide APCR. If I can find info on early APDS, I might do the same.

This topic is a bit old now but the APCR calculator on the wiki might be fixed sometime soon, maybe? At least a Senior Wikipedia Editor, part of Gaijin’s official moderator team, responded to my topic on how the calculator does not match the game.


That would be nice. Hopefully they implement my suggestion to add core data to the stat cards.


On a side note I’ve found a bug between the stated penetration of APCR rounds and their actual penetration.

From the math I’ve ran, I am fairly certain of the cause. Stat cards are using projectile diameter to calculate a caliber to thickness ratio, rather than using the APCR round’s core to calculate it. This leads to a higher C/T, which means a bit better slope modifiers, so the stat card ends up generally overestimating penetration.

More detailed explanation

APCR rounds don’t overmatch, but they do undermatch. They currently have slope effect tables for C/T ratios of 0.5 and 1, meaning that if C/T falls below 0.5, it defaults to 0.5, and the opposite if it falls above 1.

For example, at 60º the slope effects are 4.5 and 4.3 for C/Ts of 0.5 and 1 respectively.

Say you’re using M304 HVAP, which in WarThunder has a core of 38.1 mm and an actual caliber of 90 mm. If you were to shoot at a 60 mm thick RHA plate at 60º, you’d end up with a C/T of 0.635 when using the core diameter, meaning that the actual slope effect would fall somewhere between 4.5 and 4.3, closer to 4.5. Doing the math, the exact slope effect would be 4.456, giving an effective armor value of 266.76, which matches the screenshot I provided in my bug report, at 267 mm.

However, stat cards don’t use the core, they use the actual projectile diameter. This would mean that against the same plate, you’d end up with a C/T of 1.5, which defaults to the value of 1. Doing this, the slope modifier that the stat card thinks is correct ends up at 4.3, meaning that the effectiveness of that plate would be 258 mm.

I have created a simple 60º pen calculator for APCR in Desmos graphing calculator.
APCR pen calculator | Desmos
You can set C to the caliber you want (for example, you can test all I’ve said by setting it at 38.1 mm or 90 mm).
With Y you can set a flat penetration value, and the graph will provide a 60º pen value for that specific caliber.
With X you can set an armor thickness value, and the graph will provide an equivalent protection value against that caliber.

The “line” itself is separated in 3 colors for the sake of understanding. Red is for for the C/T defaults to 1, blue is for when the C/T falls between 0.5 and 1, and green is for when C/T defaults to 0.5.

The table is there purely to reference those values rather that having to repeadedly write them. This also means that if you want to test the slope modifiers for another angle, you just need to substitute the values on the table and everything will work (for example, 30º slope modifiers are 1.35 and 1.3 for C/T of 0.5 and 1).


Yeah the APCR implementation is very simplistic. It’s amazing how they managed to mess it up.


It is also telling of how typically useless it is as an ammunition type in WarThunder…

This error with the stat card has been a thing for years with APCR rounds. I only noticed now because I was a massive nerd and wanted to do an angle pen calculator in java and noticed the results I was getting in testing simply did not match the stat card.

Then I tested in game against the VK 30.02 (M) and realized that the stat card is the one that doesn’t match the actual penetration.

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Never understood why Gaijin is so insistent on anything but APHE being useless.