What do you think of the comparison table I posted, and how does it match up with your simulations?
Looks like your old graph (think you called it “third estimate”) over performs at close range. It is correct at 1000m though.
I didn’t realize at first, but since this graph tells us the velocity of projectile at two separate distance points, we can compute it’s external ballistics!
The projectile is highly aerodynamic and has a relatively low drag for it’s caliber.
Now there is a problem: the muzzle velocity for this projectile is stated to be 1100m/s, but if you extrapolate the 1135m/s at 100m data point you get the muzzle velocity of 1187m/s.
If we assume the mv. of 1100m/s, the striking velocity at 800m is now only 741m/s.
20mm DM43 ballistics
| Range (m) | (m/s) |
|---|---|
| 0 | 1100 |
| 100 | 1050 |
| 200 | 1002 |
| 300 | 955 |
| 400 | 910 |
| 500 | 866 |
| 600 | 823 |
| 700 | 781 |
| 800 | 741 |
| 900 | 702 |
| 1000 | 665 |
| 1100 | 628 |
| 1200 | 593 |
| 1300 | 559 |
| 1400 | 526 |
| 1500 | 495 |
I’ve updated the graph.
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Then maybe its with Pzgr.40 and the other core?
Idk, thats simply what the Panzerbeschuß Tafel der 2 cm KwK 30 u. 38 shows.
The difference in penetration between two cores is small, since its bigger diameter is partially compensating for a bigger mass. It’s ballistic limit only ~20m/s less, this wouldn’t drastically change it’s performance.
Soviet high hardness armour is more resistant to small caliber/subcaliber projectiles, that’s all there is to it. I sincerely doubt that the germans went to the trouble of procuring, testing armor plate from soviet tanks and changing this specific penetration value to reflect that. They most likely simply used the data they had (obtained against their own armor) in the manual.
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I stand by my predictions. We don’t know for sure why (what seem to be) test values from this german document deviate so much from the results of my model. But I know that it has worked extremely well for predicting penetration performance of myriad of other subcaliber shells, and therefore, it’s actually more (not less) trustworthy than a single historical document stating otherwise.
As far as I remember, Gaijin just equalized the penetration values for similar autocannon rounds across the board. I think they treat them as a class, ie. AP 20mm, AP 30mm, APDS 20mm, APDS 30mm, regardless of nation and manufacturing differences.
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Nice work!
I don’t know if it’s any help, but here’s the velocity table for DM48A1 Practice-Tracer and/or DM51A1 HEI-T. I’m trying to find one specifically for DM43, but no luck so far.
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Well, it also shows that the round can’t penetrate the turret front or side of a T-34-76 which doesn’t make sense. In some instances they even write “penetration only possible at near vertical angle” but not against the T-34.
They also make it so that the Shermans upper hull armor has significanlty more armor protection than the same thickness lower.
So you can’t really go by those tank penetration tables a 100% of the time.
True 🤔
I once did the math, and apparently these manuals assume that Shermans have 2.5in of armour of their upper sides. Clearly they took the maximum thickness they found (1.5in base armour + 1in applique) and used it as default value.
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Yeah, but the T-34s turret is angled upwards and rounded. Including most vehicles with the gun are a bil lower, so chances are it wont be enove to be allmost flat on.
Anyway Peasants comment is also fitting in it.
And of cource its not allways fitting.
Actually i do have another source. But that source is only like 95% of times correct.
And it sayes 40mm/30°/100m and 5mm/30°/800m (for the L/50 or L/55 barrle, the L/65 should be a bit better i suppose.)
(Im not shure what m.A.-Lauf means either mit altem lauf (meaning the later replaced L/50 or L/55 barrles or simply a allready worn barrle.)
Pro tip: it is considered a good practice in these circles to name your source whenever posting a snippet from a historical document.
Thankfully, I recognize the font, it’s from the Dokumentation-W-127-Datenblaetter-fuer-heeres-waffen-fahrzeuge-geraet
And it’s wrong. :)
At least the value for pen at 800m distance is.
This is why relying on a mathematical model can be better than on historical sources.
I don’t have FT for this projectile, but assuming external ballistics similar to those of DM43 or 5cm Pzgr.40/1 or M93 or similarly shaped APCR, the striking velocity of this projectile at 800m is 676m/s, and its penetration ~30/23mm at 0/30° respectively.
Even assuming high drag model, like that of the H>-shaped APCR, like 3.7cm Pzgr.40 (would be odd but, lets consider the possibility), its pen at 800m would still be ~14/11mm at 0/30° respectively.
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And thats why i sayed the source isnt allways right. And thats why i didnt even bother to write the name.
Ah and if you didnt knew allready here is also a rport for it. Kind of.
https://community.gaijin.net/issues/p/warthunder/i/iHHa25vbs4rl
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Wow, this is really good work and information you guys collected! It would be awesome to see this ammo buffed, as in its current state its very sad, especially when it is used on SO many vehicles. This would reallly be a boon for france, eslecially when they eventually get more AML cars.
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It says Fl-Lauf (=FlaK). It just looks like a letter A because of the quality :)
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Maybe an error and it’s suppose to say 15mm
Hello again! I did some more digging and managed to find a cross-section image of 20x139 DM63, the frustratingly enigmatic APDS projectile.
I did some shoddy pixel measurement and found a core diameter of ≈10.6mm, length ≈53.1mm. You can probably do a better job than me, the original picture is attached at the bottom of this post.
@Peasant_wb Would you be able to run a simulation on this?
Here’s some stats from Jane’s, projectile weight and so on.
Another image, showing the core itself and the windshield
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That first cut away isnt a 50% Cut away, so the pixle counting doent work. Its especially visible at the base that its “Just a Cake Piece missing”.
In other words, you cant see the full core.
Fair enough!
Here’s the other core, it’s easier to use this one
