20mm DM43 Penetration

I have started using the Marder A1 and the poor penetration of the 20mm barrel seemed quite strange to me, especially using tungsten carbide bullets and being bullets from the 60s.
First I asked a colleague who has created a suggestion to change the horrible formula for calculating penetrations for a better one, and in the calculation of the 20mm DM43 ammunition it gave a penetration of 91mm at 0º and 0 meters, then I found some images on several sites.

In this image there are several penetrations of 20 and 30mm ammunition. In the one referring to the DM43 it is seen that it penetrates 32mm at 0º at 1000 meters, while in the game the penetration is 24mm.

In these two images you can see what appears to be a German test of DM43 shots against the rear part of the turret of a T-62.The shots are at 100 meters, and the DM43 is capable of completely piercing the rear part of the T-62 turret, hitting the flattest part, and almost penetrating the areas with the most angles.

As you can see, in the game he is not able to pierce it.



It would be great if gaijin finally decided to update the penetration calculator, since there are many bullets that would achieve minor changes, but the APCR would be greatly improved, which are one of the most poorly treated bullets in the game since it came out, and which in many cases are bullets that you never use because of their extreme ineffectiveness.

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Hello @Conraire!

You made a thread about tungsten cored ammunition, so I thought it best to ping you.

This issue relates to this thread and small caliber HVAP/APDS in general.

Since the transition from table-based to calculator-based ballistics there’s been various complaints about in-game performance differing significantly from what historical documents suggest.

For example 20mm PzGr 40, flat pen used to be 64mm @10m, but after transition it became 48mm @10m.

And the source OP posted:

It shows 20mm DM63 penetrating 70mm @1000m. Whereas in-game it only penetrates 66mm @10m, and falls off to 31mm @1000m.

This suggests the calculator you use is wrong in some way, as it doesn’t match with real life examples.

Do you also see this as an issue? If so, is it possible to look into it?

Cheers!

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Imma throw this here, in case it will be useful:

Estimated performance (updated version):

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The table OP posted also shows ballistics for DM43.

It’s the first row, flat pen is 31mm @1000m

Which is funny, because that’s almost exactly what in-game DM63 penetrates at the same range.

We can also infer DM43 pen of at least 66mm @100m, since it penetrated rear of T-62 turret.

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I found this

Source:

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I found these german documents, on 20mm DM43A1, source

Machine translated:



The difference between a1 and base model is negliable, it is described on the first page.

Of note, it says the core is 70.3g

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I hope that one day gaijin decides to use a better made penetration calculator, because what they have done to this 20mm cannon is unforgivable, with the APDS ammunition it is moderately useful against other light vehicles, but with the APCR it is a complete disaster, It has a hard time penetrating light vehicles to the point of needing almost 100 bullets to destroy any enemy (I also have a theory that the server eats many of the hits), it is so bad that it is worse than a 12.7mm. What annoys me the most is that, as you can see, both the APCR and the APDS are much superior in reality than in the game, but the devs don’t bother to do anything.
I also have a question, is it possible that Gaijin has done a cut and paste with the ammunition of that 20mm cannon? I say this because it is a weapon that is in Germany, France, Italy and Japan, and I refuse to believe that any of those nations will develop their own ammunition, for example it seems strange to me that the AMX-10 uses the DM63.

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I’ve had enough of different sources telling different things, so I 3D modelled the core:

It’s volume is ~4.37cm^3, which means for 70.3g weight, a density of 16.09g/cm^3, a bit high but plausible. For 77g weight, the resultant density is 17.62cm^3, implausibly high for this kind of tungsten alloy. So, 70.3g it is.

I’ll have to re-compute it’s penetration graph. Again.

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It looks like the trajectory of in-game DM43 matches the time shown on the table pretty closely. This was my attempt to replicate the outermost curve, T = 1.24s

trajectory

Below you see my test with Marder 1A3, shooting DM43 at one of the test drive tanks, distance 1050m.

I measured the time to target in Davinci Resolve, and got ~1.19 seconds. Please take the number with a grain of salt, this is not the most precise testing method.

Found more documents, here is the source

Most interesting is this table showing penetration at different angles, at 100m and 800m distance. This projectile is not named as “DM43” but the schematics and description match it exactly.

Screenshot_20240604-102801_Firefox

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This graph is a biiig doozy.
At first, I thought it might show the performance of an alternative shell design with the core made from plain hardened steel, but this level of performance is far above what a 34g 12.7mm projectile could achieve. Especially one without a penetrating cap.

Next, a full caliber 20mm 111g projectile. It’s not as far fetched, as it might be able to theoretically defeat both a 30mm/27.5° at ~810m/s and a 45mm/30° target ~1135m/s, provided that the plate is fairly soft enough so the projectile wont shatter. But this is unrealistic as well.

Finally, I’ve settled on explanation that this test was simply carried out against a very high hardness armour.
Here are the result of the soviets testing german projectiles against medium 30 and 75mm plates and against 45mm high hardness RHA.

Spoiler

If we take the data point of the 37mm APCR against 45mm/30° as 890m/s, the DeMarre estimated BL for the DM43 against 30mm/30° is 820m/s, very close to what we see in the document.

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I find it interesting how similar Pzgr.40 and DM43 are.

Good day, here’s another document courtesy of @Conraire on the M114 thread (sorry to ping you so much!)

This is for M139 20mm cannon, which is chambered for the same 20x139mm as RH-202 meaning they share ammunition. The XM601 API-T is the US designation for DM43. m114 ammunition

Notice the API-T penetration below stated as 1 & 1/4 inches steel at 1000m. That is 31.75mm, and matches the other sources posted here previously.

m114 document

Here is the russian source giving the same number

20mm dm43

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Thats cool to see.

Overall while im not the best with post WW2 stuff, im planning to widen my info topic from WW2 to WW1, inter war and to modern-ish.
Like this one and the other 2. Where these sources will come quite handy.

True, DM43 may be a post-war development but the fundamentals are still the same!

Just looking at the schematics you see how similar they are.

The casing they are fired from are also similar, 20x138mm compared to 20x139mm

So I wouldn’t be surprised if they performed roughly the same, and that the “64mm at 10m” we used to have in game is in fact the real performance of 2cm PzGr 40

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yeah, i had the same thoughts. I mean the 20x138mmB Rheinmetall Pzgr.40 only has 4g less propellant with 49,04g to 53g of the 20x139mm.
the core is of 12mm instead of 12,7mm. The Pzgr.40 had like 3-5 generations (with also a 13mm core) and different lengths with different weight from 100g to 106g. So aside the construction similarity also similar weight to 111g.

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Do you happen to have any tables for 20mm Pzgr40?

I made comparison cards to show in-game performance (left), and what we know from sources (right)
20x139 DM63:
dm63 comparison
20x139 DM43:
DM43 comparison

(100m & 800m sourced from Rheinmetall table, 1000m from Russian table)

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Nope sry. I only know by the Panzerbeschusstafel that it can penetrate the 45mm side armor at 30° of a T-34 from 100m, which would be 1mm better than the 44mm/30°/100m of the DM43
(Or technically more than 45mm/30°/100m, because it can penetrate that cleanly and its not its limit.)

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If you look at the chart in my previous post, it also shows the results of testing the 28/20mm German atr against 45mm of soviet high hardness RHA.

It penetrated 45mm/30° only above ~1100m/s, which is above mv of the 2cm Pzgr. 40