Modification of AP calculator

[MiseryIndex556@psn 13,154]

My suggestion is to modify the current armor penetration calculator to better represent AP performance. With the adoption of the formula system, the performance of AP and APC rounds were made uniform, disregarding historical documentation. While this has reduced the work to implement new rounds and eliminated debates about penetration standards. The downside is specific round performance is no longer historical. The issue is further compounded by the use of standard slope modifiers. The slope modifiers come from WWII Ballistics, Armor and Gunnery. They are dependent on the penetration data from the same source. The issue starts with how Gaijin implemented its formula. Instead of calculating the necessary theoretical penetration for the standard WWII BAG slope modifiers to work, Gaijin attempted to account for certain AP rounds shattering. The "shattered" vertical penetration is reduced from the theoretical penetration of the round. When that reduced vertical penetration is applied to the standard slope modifiers, the sloped performance of the round is also reduced. In many cases, the shattered vertical penetration performance is accurate, but the reduced sloped penetration is not. In other cases, the round did not shatter against vertical armor, so both its vertical and sloped penetration is incorrect. This issue can be addressed by removing the "shattering" modifier from the AP round version of the calculator and changing the K factor to 1800.

 

Based on work I have done for previous reports, I have been able to establish a few key factors in the AP formula. First, the formula uses a K factor of 1900. Second, the uncapped AP formula applies an additional .9x modifier to the result. That .9x modifier is to represent the shot shattering.

 

Here's a screenshot of the formula results. First is the AP results, then the same round with the APCBC box check. AP is 174.75, APCBC is 194.17. 174.75/194.17 is .8999 or rounded up to .9.

Spoiler

 

 

Here is a screenshot of a Demarre calculator with the K factor set to 1900. In this version, the "a" variable is the K factor. As you can see, the standard result is 194.17, which is the APC result. The AP result is 174.75. Both results match the calculator results from Gaijin.

 

Spoiler

 

 

Next, we need to establish a basis for the 1800 K factor. I'll use 90mm T33, since its a well documented round. The 90mm T33 will defeat the 80mm Panther glacis plate to roughly 1400 yards. This is shown by the following document. The penetration chart below shows the 90mm T33 will pen the 3.15" (80mm) at 55 degree glacis plate to about 2425 feet per second. The chart is based on US navy criterion, so the standard is pretty strict. Its a good basis for the performance of the round.

 

Spoiler

 

Using the in game armor protection analysis, we can see the Panther glacis equates to 171mm of protection against the 90mm T33. 

 

Spoiler

 

Using the Demarre formula to change the penetration at 2425 fps to the muzzle velocity of 2800 fps, we get the following penetration.

 

Spoiler

 

Now, going back to our Demarre calculator, with the K factor set to 1800, we get the following results for 90mm T33 at 2800 fps. The results are basically identical, with a little rounding.

 

Spoiler

 

To verify the results, we can look at another round. 57mm M70 AP is not prone to shattering, so we can use it as a good reference. The navy criterion chart is below.

 

Spoiler

 

At its muzzle velocity, the M70 AP penetrates a little over 5.5" or 140mm of vertical armor. Using the 1800 K factor, we get the following result.

 

Spoiler

 

The result is slightly higher but I think a reasonable estimate.

 

To sum up the report, I suggest changing AP performance to allow for historical sloped penetration. This would be achieved by changing the K factor from 1900 to 1800 and removing the .9x modifier. 

Edited October 6, 2022 by MiseryIndex556@psn

[MiseryIndex556@psn 13,154]

For reference, here is how a few other US AP rounds would look at muzzle velocity and against vertical plate. Also listed are other rounds available.

 

37mm M74B1: 94mm M51B1: 87mm

57mm M70: 142mm M86: 122mm

75mm M72 (M2 gun): 101mm M61: 97mm

75mm M72 (M3 gun): 109mm M61: 101mm

76mm and 3" M79: 162mm M62: 149mm M93: 190mm

90mm M77: 195mm M82: 173mm M304: 287mm

90mm T33: 210mm M82: 173mm M304: 287mm

90mm M318: 211mm M82: 185mm M332: 321mm M348: 305mm

90mm M318A1: 232mm M82: 185mm M332: 321mm M431: 320mm

90mm T43: 254mm T41: 224mm T44: 336mm

105mm T182: 320mm T279: 318mm T298E1: 380mm

120mm M358: 362mm M469: 380mm
 

As you can see, either the increased AP performance is still close to the APC rounds used, or is outclassed by other rounds, such as APCR and HEATFS. The balance change would be minor, other than allowing the rounds to perform as intended.

Edited October 6, 2022 by MiseryIndex556@psn

[MiseryIndex556@psn 13,154]

And just to demonstrate that these values are needed to function with the WII Ballistics, Armor and Gunnery slope modifiers, here is their table for US armor piercing rounds used in WWII. The values I calculated are at the muzzle. The charts show the closest penetration values at 100 yards, which accounts for my values being higher.

 

Spoiler

 

Edited October 30, 2022 by MiseryIndex556@psn

[leroyonly 4,311]

Open for discussion. 

[MiseryIndex556@psn 13,154]

Thanks 

[MH4UAstragon 9,581]

@MiseryIndex556@psn thank you for making this. I can say without a doubt that some modifications to the AP calculator are sorely needed.

 

What I always relied upon was this calculator by @KillaKiwi, which he made, but I filled in the info for all ingame shells. Given that there were some discrepancies between different nations' testing standards of what constituted a full penetration, perhaps a merger of this and your idea is in order? Maybe using a wholly different calculator is not practical at this point in the game's life. The linked one accounts for differences in shell design between Russian shells and most other nations, where currently the flat-nosed AP rounds comically overperform, and when the mere hint of any other nation getting the same slope modifiers on APBC became even a slight possibility, Gaijin promptly gave all the Italian and American APBCs a different slope modifier, right after the T30 released. I don't prefer to jump on the whole "Russian Bias" train, but seeing that episode really made me consider doing so.

 

I do wish that the actual formula the Gaijin calculator was using was shown above each set of calculator input boxes, this would make the lives of those who care about getting these numbers at least "close enough" right so much easier.

 

If nothing else, perhaps there should be a checkbox for "flat-nosed penetrator" or not, since the effect on vertical penetration is pretty damn substantial. 

 

Finally, the Gaijin APCR calculator is just plain wrong on so many levels, and needs outright immediate replacement. The "original shell mass" part literally does not matter to how much the round pens because the APCR jacket is just mild steel that is squished out of the way upon impact, too soft to contribute meaningfully, much like the cap and ballistic windshield steel of full-caliber rounds.

 

With proper penetration values, particularly on subcalibers, at least three whole BRs worth of decompression space would become immediately and unavoidably necessary. Without being propped up on their cracked slope modifiers, Russian tanks would plummet in BR rather quick. Some German ones may drop as well when suddenly far more of their opponents make utter mincemeat of their armor than previously. As would armor bricks in other nations that cannot move to save their lives (T28, T95, Tortoise, Black Prince, etc). Hence why I voted for the option of "support pen calculator changes with BR adjustment."

Edited October 26, 2022 by MH4UAstragon

[MiseryIndex556@psn 13,154]

@MH4UAstragon I get what you’re saying and would agree, if Gaijin was not using the standard slope modifiers. If you don’t use the corresponding vertical penetration, the slope modifier system won’t produce reasonable results. If we replace the current system with another that generates results that also don’t match WWII Ballistics, then we will still have incorrect results. From what I remember of Killa’s work, I generally agreed with it but not in the context of the current system. 
 

War Thunder does not account for bad designs, bad materials or part failures. The same must apply for AP rounds, as it does for APC and APC-HE. That’s the only way this current implementation will work. 

Edited October 26, 2022 by MiseryIndex556@psn

[AlanHR 5,261]

Definitely YES with BR changes if needed.

[MiseryIndex556@psn 13,154]

@Smin1080p can we get this forwarded? Fixing the calculator is necessary for proper AP performance. 

[MH4UAstragon 9,581]

On 19/12/2022 at 17:27, MiseryIndex556@psn said:

@Smin1080p can we get this forwarded? Fixing the calculator is necessary for proper AP performance. 

I second this bump - getting all ammo types onto the calculator was the hard part, now fixing how the calculator works would make a lot of people happy.

[MiseryIndex556@psn 13,154]

5 hours ago, MH4UAstragon said:

I second this bump - getting all ammo types onto the calculator was the hard part, now fixing how the calculator works would make a lot of people happy.

It’s an easy fix. That’s the frustrating part. 

[MiseryIndex556@psn 13,154]

There are a number of Youtube channels that run simulations of AP performance and a they have done T33 and M358 AP videos. These videos closely correspond with the formula changes I am suggesting.

 

Here is 90mm T33 against a Panther inclined at 5 degrees.

Spoiler

 

And here is a chart I made using the Gaijin formula, modified as I am suggesting, and the slope modifiers used in game. Green means the round will penetrate. Red means the round will not penetrate.

 

The round does not quite penetrate. Some of the fragments do but most bounce off the glacis. My chart shows that it would not be able to penetrate, using Navy standards.

 

Another example is 120mm M358 against the IS6.

Spoiler

 

And here is my chart

 

The 100mm plate would require about 316mm of pen to defeat, with my calculator only showing 314, however, the round is falling at about .5 degrees, so that would reduce the slope and help defeat the plate.

 

Either way, I think these two simulations show how reasonable my suggested changes are. It may not be perfect but would allow a much more realistic performance from the rounds, in their intended roles.

[KillaKiwi 5,478]

1 hour ago, MiseryIndex556@psn said:

Either way, I think these two simulations show how reasonable my suggested changes are. It may not be perfect but would allow a much more realistic performance from the rounds, in their intended roles.

Yeah but what about vertical penetration though?

Between 0-40°, APC should outperform AP and at 30° greatly, especially at high velocity.

 

I remember some US document about how APC LoS penetration decreases with angle, while with AP it will start to increase at around 40-45°, meaning that AP is able to defeat more sloped armor than vertical armor. So maybe we need some modifiers to reduce penetration at low obliquity impact.

 

And it should be noted that the post-pen damage of high angle penetration, near the shells capabilities, are generally poor, since a lot of the spalling will be directed to the normal of the plate as the shell breaks apart and is deflected from the plate and fragment velocity will be low.

So it will pepper the driver with lethal fragments and maybe hit some ammunition stored at the floor but it would be hard to knock out crews.

Keeping that in mind, it would also be nice, if APHE rounds wouldn't fuze under these conditions, since the impact forces when impacting sloped armor will generally render the fuze inoperative.

But in my world, APHE of course wouldn't knock out the entire crew with one round :P

 

 

[MiseryIndex556@psn 13,154]

3 hours ago, KillaKiwi said:

Yeah but what about vertical penetration though?

Between 0-40°, APC should outperform AP and at 30° greatly, especially at high velocity.

 

Only if the AP shatters. Rounds like M318 don’t shatter, so their performance is higher than M82. Same with 57mm M70 AP and M86. M77 AP had better vertical pen than T33 and M82. Even then, if the AP did over perform, it wouldn’t be better than APCR, so the balance difference is minor. Some AP would over perform against vertical armor, just like plenty of APC rounds are over performing against vertical armor. 

 

3 hours ago, KillaKiwi said:

 

I remember some US document about how APC LoS penetration decreases with angle, while with AP it will start to increase at around 40-45°, meaning that AP is able to defeat more sloped armor than vertical armor. So maybe we need some modifiers to reduce penetration at low obliquity impact.

 

US documents said AP outperforms APC at all obliquities at 1 T/D and below. 

 

3 hours ago, KillaKiwi said:

 

And it should be noted that the post-pen damage of high angle penetration, near the shells capabilities, are generally poor, since a lot of the spalling will be directed to the normal of the plate as the shell breaks apart and is deflected from the plate and fragment velocity will be low.

So it will pepper the driver with lethal fragments and maybe hit some ammunition stored at the floor but it would be hard to knock out crews.

Keeping that in mind, it would also be nice, if APHE rounds wouldn't fuze under these conditions, since the impact forces when impacting sloped armor will generally render the fuze inoperative.

But in my world, APHE of course wouldn't knock out the entire crew with one round :P

Gaijin is not going to abandon the current calculator and slope modifier system. This is the best chance of getting AP rounds like T33 to be useful. It’s not perfect but it’s better than the current outcome. 

[KillaKiwi 5,478]

33 minutes ago, MiseryIndex556@psn said:

Rounds like M318 don’t shatter,

Ok, tell me one other round that doesn't shatter. Because 99% of AP we have in-game will

34 minutes ago, MiseryIndex556@psn said:

US documents said AP outperforms APC at all obliquities at 1 T/D and below. 

Well, that's something. Should be possible to reduce the performance of AP above 1.0 T/D ratio then compared to APC.

 

36 minutes ago, MiseryIndex556@psn said:

Gaijin is not going to abandon the current calculator and slope modifier system. This is the best chance of getting AP rounds like T33 to be useful. It’s not perfect but it’s better than the current outcome. 

And what will happen with APHE rounds? They will be better than APC-HE leading to some weird overperforming in-game.

T-34-85 and Chi-Nu IIs with 180mm of penetration, just cutting right through the mantled of Tigers or even Churchill Mk VIIs.

Ho-Ri Production with near 300mm penetration that easily cuts through any T-54 or IS-3.

[MiseryIndex556@psn 13,154]

45 minutes ago, KillaKiwi said:

Ok, tell me one other round that doesn't shatter. Because 99% of AP we have in-game will

 

I just listed a few. 
57mm M70

75mm M72 I need to check ballistic limits again

76mm M79

90mm M77 didn’t shatter against vertical armor

90mm M318 and M318A1

Possibly 105mm T182 didn’t shatter. 

 

45 minutes ago, KillaKiwi said:

Well, that's something. Should be possible to reduce the performance of AP above 1.0 T/D ratio then compared to APC.

 

And what workaround do you propose for sloped performance? 

 

45 minutes ago, KillaKiwi said:

 

And what will happen with APHE rounds? They will be better than APC-HE leading to some weird overperforming in-game.

T-34-85 and Chi-Nu IIs with 180mm of penetration, just cutting right through the mantled of Tigers or even Churchill Mk VIIs.

Ho-Ri Production with near 300mm penetration that easily cuts through any T-54 or IS-3.

Then only use it for solid AP. 

Edited January 23, 2023 by MiseryIndex556@psn

[Abrams_X 1,234]

51 minutes ago, KillaKiwi said:

Ok, tell me one other round that doesn't shatter. Because 99% of AP we have in-game will

Well, I need to say this, that the game doesn't model something like a `poor quality prone to shatter` or a `material composing a projectile` in case of full-calibers.

Which means the game will always assume that a projectile is made of best possible material available and won't shatter at impact.

If `shattering of a projectile` was actually a thing in game, then the 128/88 PzGr. TS wouldn't achieve such a high penetration.

[Conraire 5,723]

I'm personally not against proposals to change the AP calculator. I think I'm the only one so far that's voted for the 3rd poll option..

 

But, you're fighting an uphill battle, and you're going about it the wrong way, just as all those before you have.  You're only looking at things from the effects it would have on US solid shot AP ammo, you don't seem to be taking into account the effects it would have on other ammo types that it is used for.  Especially when changing the a/k factor.  

 

The only real modification I think the calculator needs, is a redesign and re-evaluation of how the burst charge penalty is applied, as well as removing the 0.9 modifier for non apcbc rounds. APCBC rounds should have a 0.95 modifier applied to correct for the fact that a percentage of their mass is impact cap.  Then shells with HE burst charges should have a minimum 2% penalty to a maximum 5% penalty depending on shell weight to charge weight ratio, this would more correctly reflect what is suggested in WW2BAG.  Certain shells in game currently receive no penalty from having a burst charge cavity, because the burst charge doesn't take up a high enough mass to mass ratio.  Which doesn't make sense, as regardless of how small a burst charge is, putting a burst charge cavity in the base of a shell still reduces it's structural integrity.  

 

These are just some examples of what would happen with other shells when changing the a/k factor.  And also some examples of the current values with the penalties reevaluated.

 

I haven't had a chance to look over german velocity tables and calculate their shells with these suggestions yet.

[MiseryIndex556@psn 13,154]

That’s a fair point but I didn’t arbitrarily pick the K factor. I used known quantity points to establish it. It can be restricted to solid AP to avoid any further issues. 
 

I am focused on US AP because so many tanks use it and it has been an issue for a long time. 

[Conraire 5,723]

12 hours ago, MiseryIndex556@psn said:

That’s a fair point but I didn’t arbitrarily pick the K factor. I used known quantity points to establish it. It can be restricted to solid AP to avoid any further issues. 
 

I am focused on US AP because so many tanks use it and it has been an issue for a long time. 

 

The Devs won't change the K/a factor for a single ammunition type, if at all.  Other people have already been through that and tried, including people you know. 

[MiseryIndex556@psn 13,154]

So we just are stuck with a terrible one size fits all system? 

Edited January 23, 2023 by MiseryIndex556@psn

[KillaKiwi 5,478]

4 hours ago, MiseryIndex556@psn said:

So we just are stuck with a terrible one size fits all system? 

Well, it's not so bad. As long as each shell type acts, like they are suppose to:

1. AP -> All around effective but worse than APC for T/D ratios above 1. (Very bad against FHA)
2. APC -> increased vertical penetration for reduced slope armor penetration. (Great against FHA)
3. Flat nosed AP -> Worse than AP for T/D ratio above 1 but better than AP below 1
4. APCR -> Basically like APC but extreme difference between flat and sloped penetration

We just need some more variables taking in to account.

I'm not really sure, if bursting charge should be a deciding factor at all. At least not for vertical penetration.

Take the 128mm Pzgr. or Pzgr. 43. Just by taking away the huge penetration cap and only looking at the mass of the penetrator, it will have nearly the same performance it has now with the explosive mass penalty.

The 128mm Pzgr. 43 penetration cap is well over 15% of the entire shell mass. Same with the M62, which penetrates way more than it should be capable off, because Gaijins only looks at the shell weight but not the penetrator weight.

The Italian 75mm weighs 6.3kg vs the 6.8kg of a similiar German or US shell already, because it has such a huge bursting charge. So the shell is already has less penetraiton.

 

57mm APHE for the Japanese would be able to penetrate significantly more. A 350m/s shell is not going to break up on 30mm of armor because of its bursting charge.

 

 

[MiseryIndex556@psn 13,154]

You can’t just assume all AP shattered, because not all AP shattered and then it still won’t work with the standard slope modifiers. 
 

The standard modifiers require shatter being ignored. 
 

Gaijin wants a paint by the numbers system but is trying to color outside the lines. Probably because making AP as painful as possible is a good money generator. Forcing players to grind purposely nerfed rounds so they get tired and throw gold at it. 

Edited January 24, 2023 by MiseryIndex556@psn

[KillaKiwi 5,478]

11 hours ago, MiseryIndex556@psn said:

Gaijin wants a paint by the numbers system but is trying to color outside the lines. Probably because making AP as painful as possible is a good money generator. Forcing players to grind purposely nerfed rounds so they get tired and throw gold at it. 

Could be. APHE is just ridiculous and it got even worse since APHE can now overpressure, knocking out the entire crew, regardless where it penetrates the fighting compartment.

At the same time, Gaijin is just very incompetent when it comes to implemantation of rounds, at least of air and ground and changes are very slow.

 

11 hours ago, MiseryIndex556@psn said:

You can’t just assume all AP shattered, because not all AP shattered and then it still won’t work with the standard slope modifiers. 

Most did, and I'm not even sure, those rounds you mentioned were an exception, because I highly doubt that US WW2 AP rounds would not shatter when striking 30° armor.

57mm M70 AP requiring 2800fps (852m/s) to penetrate 76mm of armor at 30° is pretty much a testimony of the shell shattering.

Against the same plate and higher hardness the shell requires less velocity since hard armor is basically worse than soft armor, if the soft armor is already able to deform or shatter the shell on impact, since the hard armor can't absorb as much energy via plastic deformation.

[MiseryIndex556@psn 13,154]

I posted the Navy pen chart for M70 AP in the first post. It’s the second to last spoiler and shows M70 penning 3” of 30 degree plate at around 2,200 fps. Those graph lines are dead straight, meaning little if any shattering. And that’s Navy standards, not Army standards.

 

Even if the rounds did shatter, that is irrelevant for the system Gaijin chose to implement. It only works if the rounds are treated as if they didn’t shatter. We can suggest some kind of variable modifier that reduces pen of rounds that did shatter, but uses non shatter performance for sloped calculations.