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.

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.

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.

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.

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.

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.

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.

@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):