# Overhaul of Gaijin calculator

One aspect is I’m trying to minimize the changes needed to hopefully get Gaijin on board. I don’t want to push for a major, complex system they won’t want to do.

Also, this kind of complex work is beyond my excel skills, so I don’t know how to set up the formulas for variable penetration based on filler to shell weight ratios or t/d ratios.

The sequel to one of my old posts in this thread has dropped:

The cap appears to have a considerable effect on penetration of thin, highly sloped armour here. It’s mass % seems to not be as important as its external shape, more angular being better.

On other other hand, its effect on normal impact can be easily modelled by taking into account just its relative mass %. It appears that it’s effect is weakening with increase in T/D ratio, or the striking velocity, which seems more likely. We can hypothesize that the amount of energy it is subtracting from the shell is not proportional to its initial energy, but is an absolute fixed amount. Therefore, as the striking energy gets higher, the relative amount by which it is increasing the ballistic limit is decreasing.

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One of the conclusions that is stated on ADA954868 “Comparative Effectiveness of Armor-Defeating Ammunition” is that capped steel shots are better than uncapped steel shots when it comes to penetrating heavily undermatched angled armor. At the bottom of page 3, the following is stated:

Capped steel shot are superior to monobloc steel shot for the defeat of greatly overmatching armor, (over 1-1/4 calibers in thickness) at obliquities in the range of 20° - 45°, but both capped and monobloc shot are greatly inferior to HVAP shot in the low obliquity range against heavy armor targets.

I guess the shape of the cap just makes it easier to transfer energy into the armor without getting deflected. I imagine the same result from flat nosed shells.

Hence why Germany really wanted capped shells to defeat those evil 30° plates.

The same source also states that sharp nose rounds tend to perform better against thicker armor that overmatches the projectile while blunt nose rounds tend to perform better against thinner armor that undermatches the projectile.

An important consideration in the penetration of armor by kinetic energy projectiles is the ratio of armor thickness to projectile diameter (the e/d ratio) since the mechanisms of armor penetration and projectile behavior vary with the e/d ratio. When the e/d ratio is greater than 1 (armor overmatches the projectile), the penetration tends to be effected by a ductile pushing-aside mechanism. Relatively sharp nosed shot are most effective, and the resistance of the armor generally increases as its hardness increases. When the e/d ratio in less than 1 (armor undermatches the projectile), the penetration tends to be effected by the punching or shearing out of a plug of armor in front of the shot. Relatively blunt nosed shot are most effective under this condition of attack, and the resistance of the armor generally increases as its hardness decreases.

This isn’t quite reflected in the game, as blunt nose rounds can perform better against thicker armor armor if the angle is lower. It only really applies for very thick armor at extremely high angles, and against very thin armor uncapped sharp nose AP has an advantaged at very low angles but loses the advantage at higher angles. These tables are taken from a calculator I made, with the values themselves being taken from Gzsabi’s datamine github repository, and have the angle at the top and the caliber divided by the armor thickness at the right.

Sharp nose, uncapped AP:

Blunt nose AP:

Yes, blunt nose AP has an armor multiplier of 1690 against armor at an angle of 85 degrees when the armor is twice the caliber of the projectile itself. No this doesn’t matter because against armor that thick the ricochet is already 100% at a much lower angle.

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But you said:

Doesn’t that make it pretty useless? 😂

What’s the application?

That’s pretty interesting. Using your chart, it matches my suggestion pretty well.

161mm using the PzGr 39/42 compared to 162mm for the modified DeMarre formula.

I mean, that’s not surprising. This method is not supposed to change the results given by de Marre formula by a lot. Changing the ballistic limit by +3% at most will change penetration by only +4.3%

The discrepancy that you see here is not a random fluke, I’ve seen it before. The ballistic limit in the DeMarre formula is assumed to be proportional to the 0.7-th power of T/D ratio, not the ~0.62 seen here.

But this is not an error in the formula, it is a deliberate choice.
The armor plates used in these tests are all about the same tensile strength / hardness (the two are approximately directly proportional), while the nominal BHN of armor plates manufactured for real vehicles decreases as their thickness grows. Because of this the data points for such armour would move a bit downwards in the lower T/D range and would make the overall trend be steeper and therefore the required exponent would be higher than 0.62.

Beyond 150mm thickness the tensile strength of german penetration testing plate is constant and using DeMarre-like formula in this region requires appropriate adjustments.

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Another interesting tidbit:

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What are we looking at?

Are those penetration estimates or test data?

So Y axis is K factor? What’s this n=1.22?

Also whats the conclusion?

I’m guessing the line represents the dependency of K factor to the armor hardness for more accurate penetration estimations, in the case of 37mm APC?

Yes, this is experimental data. Source for this graph is the same as last one. The line is a linear trend model fitted through the data set using the “least squares” method.

The point is to have solid evidence, and not just intuition, that the K constant can take different values, with neither being the correct of wrong one.

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Hello, I will link this topic here as it is related!

It’s about low-caliber HVAP/APDS, and how Gaijin’s calculator doesn’t match the sources:

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Another reason why the NPL formula is better. (at least, for scenarios where its applicable)

Yeah adding ballistic limits would be so nice, instead of all rounds just penetrating impossible amounts of armor at higher velocity.

But I feel like that is never going to happn with WT.

I mean you know:

• RoF is a balance factor
• Everything can be repaired etc.

Huh? I think we are talking about different things. Yes, the high velocity guns do currently somewhat overperform in this game, but that’s not what “ballistic limit” means. It’s just another way to indicate the limit velocity for perforation.

I don’t get what this graph is showing.

The y axis is the ratio of 30 degree ballistic limits to 0 degree ballistic limits. The x axis is the thickness to caliber ratio.

A plate that is .5 times diameter will have a 30 degree ballistic limit that is the same as its 0 degree ballistic limit. A plate that is 1.0 times diameter will have a 30 degree ballistic limit that is 1.125 times its 0 degree ballistic limit.

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Oh, I see.

Well in game that’s taken care of using slope effects, rather than the calculator itself.

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@MiseryIndex556 I recently did the number-crunching for the majority of large (100mm or bigger) HE rounds using Gaijin’s calculator, and surprisingly enough the calculated armor penetration for such rounds lines up rather strongly with occasions in historical record.

Even the biggest HE shells only are about 10-20% filler weight by mass. The rest of the shell mass doesn’t just go “POOF” upon impact, but rather has penetrating effects like low-ish quality AP.

The 122mm OF-471 was stated “to be as effective at tank-killing as the (BR-471) AP.” German 128mm HE at max propellant charge of 880 m/s punched through 188mm of flat steel.

Running those numbers through Gaijin’s calculator gives 154mm kinetic pen on OF-471 and 184mm pen on 128mm HE.

Are there any compiled documented sources for this type of penetration test for HE rounds? Beyond those two examples from German sources, there isn’t really much that I could find, but maybe I just don’t know where to look.

And also, should a Suggestion to “apply the DeMarre penetration calculator to HE rounds” be lumped in with this suggestion or should it be a separate one?

In case you wish to merge DeMarre’ing HE rounds into your broader overhaul, I ran the numbers already (attached below):

Spoiler

America:

Spoiler
• 105mm M4, M1 HE shell: 59mm + 27mm blast
• 114mm M8 Rocket: 27mm + 24mm blast
• 105mm T5E1, T30E1 shell: 163mm + 20mm blast
• 120mm T53, M73 shell: 186mm + 29mm blast
• 120mm M58, M356 shell: 139mm + 39mm blast
• 155mm T7, M107 shell: 152mm + 61mm blast
• 155mm M126E1, M107 shell: 107mm pen + 61mm blast
• 155mm M185, M107 shell: 142mm + 61 mm blast
• 152mm Gun/Launcher M81, M657A2 shell: 90mm + 38mm blast
• 127mm HVAR rocket: 108mm pen + 36mm blast
• 298mm Tiny Tim: 114mm pen + 74mm blast

Germany:

Spoiler
• 150mm s.I.G.33, I.Gr.38 shell: 30mm pen + 61 mm blast
• 105mm StuH42, F.H.Gr shell: 59mm pen + 22mm blast
• 150mm W.Gr. 41 Rocket: 46mm pen + 27mm blast
• 105mm K.18, Gr.19 shell: 136mm pen + 23mm blast
• 128mm K.40, Sprgr. L/5 shell: 184mm pen + 37mm blast (Compares well to above example)
• 128mm KwK44/PaK44, Sprgr. L/5: 146mm pen + 37mm blast
• 380mm RW61 mortar, 38cm R Spgr.4581 rocket: 56mm pen + 82mm blast
• 105mm KwK46 L/68, Sprgr. L/4.4 shell: 151mm pen + 20mm blast
• 210mm Wfr.Gr. 21 rocket: 68mm pen + 62mm blast

Russia:

Spoiler
• 420mm TT-250 rocket: 17mm pen + 83mm blast
• 122mm M-30 howitzer, OF-462 shell: 75mm pen + 37mm blast
• 152mm M-10T howitzer, OF-530 shell: 95mm pen + 48mm blast
• 152mm ML-20S, OF-540 shell: 137mm pen + 49mm blast
• 107mm ZiS-6, OF-420 shell: 118mm pen + 27mm blast
• 130mm B-13, OF-46 shell: 201mm pen, 36mm blast
• 152mm 2A33, 3OF25 shell: 137mm pen + 62mm blast
• 122mm A-19/D-25, OF-471: 154mm pen + 37mm blast (Compares well to above example of being “equally effective at tank-busting compared to the AP”)
• 122mm 2A31, 3OF24/56: 133mm pen + 51mm blast
• 100mm D-10, OF-412 shell: 163mm pen + 19mm blast
• 152mm M-64, OF-540 shell: 166mm pen + 49mm blast
• 130mm S-70, OF-482M shell: 211mm pen + 37mm blast
• 152mm M-69, 152mm HE shell: 236mm pen + 49mm blast
• 152mm LP-83, HE: 231mm pen + 61mm blast
• 132mm M-13 rocket: 65mm pen + 40mm blast

Britain:

Spoiler
• 178mm Hedgehog Mortar: 34mm pen + 65mm blast
• RP-3 rocket: 36mm pen + 44mm blast
• 183mm QF L4A1, Shell L1 HESH: 183mm pen + 65-70mm pen blast
• 165mm L9A1 demolition gun, L33A1 HESH: 26mm pen + 65-70mm pen blast
• 155mm G6 L/45, M1 shell: 217mm pen + 63mm blast
• Uncle Tom, Triplex RP: Comparable to Tiny Tim, but diameter isn’t shown ingame
• Red Angel: AP-based penetration value already listed ingame, 168mm pen + 70mm blast

Japan:

Spoiler
• 150mm Type 38 Howtizer, Type 92 HE: 37mm pen + 55mm blast
• 120mm Schneider-Canet 1898, HE: 86mm pen + 25mm blast
• 120mm Navy Short Gun, Short HE: 23mm pen + 31mm blast
• 120mm 10th Year Type, Ordinary Mod.1 HE: 143mm pen + 25mm blast
• 105mm Exp/Type 5, Exp. HE: 162mm pen + 30mm blast
• 155mm NSJ L/30, M107 HE: 112mm pen + 61mm blast
• 155mm NSJ L/30, Type 75 HE: 154mm pen + 54mm blast
• 155mm JSW L/52, both HE shells: 223-224mm pen + 61-64mm blast
• 130mm Type 75 rocket: 176mm pen + 51mm blast
• Japanese Type 5 No.6 aircraft rocket calibers are also not known

China (only one unique gun):

Spoiler
• 120mm Type 71, 120-HE: 149mm pen + 33mm blast
• PLZ-83 uses the Russian 152mm ML-20S cannon
• PLZ-83-130 uses the Russian S-70 cannon

Italy (also only one unique gun, why the 105/25 M43 has no HE is beyond me, real gun probably does):

Spoiler
• 100mm Cannone da 100/17, Granata Mod.32 HE: 46mm pen + 27mm blast

France:

Spoiler
• Lorraine 155 uses the same gun as the M109G
• 100mm SA47 L/58, Obus explosif: 182mm pen + 18mm blast
• 142mm ACRA, MUC HE rocket: 103mm pen + 36mm blast
• AMX-50 variations use the M103’s cannon
• 155mm GCT F1, OE 155 56 HE: 183mm pen + 54mm blast

Sweden:

Spoiler
• 114mm Psv.H/18 howitzer, akr 32/41 HE: 35mm pen + 25mm blast
• 150mm m/02 recoilless rifle, sgr m/38 HE: 38mm pen + 48mm blast
• 105mm kan m/44, sgr m/44 LT HE: 51mm pen + 23mm blast
• Same as above on Ikv 103 w/ lower velocity: 40mm pen + 23mm blast
• 155mm kanon m/60, sgr m/60 shell: 209mm pen + 58mm blast
• 150mm m/51 rocket: 97mm pen + 39mm blast
• 180mm m/49 rocket: 92mm pen + 43mm blast

Israel:

Spoiler

Nothing unique