KillaKiwi

Realistic performance of Soviet flat nosed AP shells (APBC)

Edit: 17.11.2018

I've made a Google spreadsheet for better visualisation:

https://docs.google.com/spreadsheets/d/18nvGzRSXFTok9knnXGbRTwWzDo_bdDAFa_H5Riyw6gI/edit?usp=sharing

Just naviagte to the APBC sheet.

 

 

I created this topic to present and discuss information regarding the performance of Soviet flat nosed AP shells.

It also serves to gather information for a future bug report if those shells turn out to have the wrong performance.

 

The current performance of Soviet flat nosed AP shells comes from the book WW2 Ballistic: Armor and Gunnery which presents the performance of these types of shells based on one penetration graph from US tests with the Soviet 122mm BR-471B shell:

Spoiler

BR-471B vs US RHA WW2B.jpg

 

All other Soviet flat nosed shells are based on this perfomance and also their performance against sloped armor.

WW2 Ballistics uses these formulas to calculate the 0° penetration of these various projectiles. (Ignore the red rectangle)

image.thumb.png.b9802a4d0dd863e2c98ac0fb

 

However there are multiple mistakes that were made using the US chart:

  1. The chart uses Army Protection criteria instead of Navy penetration criteria. (However against high obliquity, Protection and Navy criteria should have the same results)
  2. The RHA armor used is not your typical WW2 RHA armor but infact very hard. 1.) 2.)
  3. Flat nosed projectiles have increased performance against very hard armor. 3.) 4.)

 

From http://tankarchives.blogspot.com/2013/11/shell-shape.html:

Quote

Homogeneous armour, armour with uniform hardness, resists blunt shells much better than sharp shells. On tanks of all countries, including Germany, armour is homogeneous, which means that using sharp tipped shells will be more effective than blunt tipped shells. Sharp tipped shells also have an advantage when fired at an angle, which happens most often. A blunt nosed shell that hits armour at an angle ricochets. A sharp nosed shell, when hitting the armour, bites into it, and penetrates.

(...)

I think that it is imperative to immediately begin production of sharp-tipped armour piercing shells for anti-tank artillery.
June 27th, 1942
V. Malyshev"

 

So sharp tiped AP performs better than blunt nosed AP both against flat armor and at an angle.

How is this possible? The answer is simple:

 

Against regular RHA armor that is not particular hard and therefore not brittle, the armor resists the shell by absorbing the energy by bending.

A sharp tip pushes the armor out of the way while a blunt nosed shell experiences more resistance since it has to push more armor.

Against sloped armor that overmatches the projectile, the armor resistance is so great that the projectile can't get a grip into the armor, the shell ricochets while a sharp shell penetrates the armor.

However if the angle is increased, the armor gets thinner and the blunt shell might perform as well as a sharp nosed shell or possibly better.

 

The real advantage of blunt shells is the ability to penetrate hard armor more easily.

Soft armor is like dough, it absorbs the impatct by deforming, the thicker the plate the more energy is required to deform it.

Hard armor is like glass, it won't budge when something soft tries to deform it. However exceed a critical point and the glass will shatter.

While you can easily punch a whole into dough with a pencil, the pencils tip will break against the glass. You will need a lot of force to break the glass with a pencil.

On the other hand if you use a hammer, you can easily shatter the glass without much effort while against dough the hammer is a lot less effective.

The dough absorbs the energy since the hammer has much bigger area that is in contact with the dough compared to the pencil that pierces through it.

 

So we can see how blunt shells can defeat hard but brittle armor a lot easier than sharp shells but perform poorly against soft armor.

 

From my topic about AP and APC performance we saw how US 90mm T33 AP shell should penetrate ~222mm of armor (energy wise) if the shell wasn't going to shatter.

With the added ballistic cap the round is able to penetrate the Panthers armor between 1000-1200m having a slope modifier of ~2.30 against 55° armor.

 

According to Soviet tests at Kubinka the 100mm AP shell could penetrate the Panthers armor up to 1600m.

If we compare the performance of the US 90mm AP to the Soviet 100mm AP using de Marre we see that the shell should in theory penetrate 283mm of armor at 0m

With the ballistic factor of the 100mm AP it would penetrate around 180mm of armor at 1600m which would mean a slope modifier of ~2.26. Just slightly better than 90mm AP.

The actuall performance against flat armor for both shells is of course lower since AP shells start to shatter when armor overmatches them by around 2.0 times or even 1.0-1.2 times at 30°.

 

In WW2 Ballistic they also have another graph for a Soviet blunt nosed shell. The 100mm BR-412B.

Spoiler

100mm_APBC_penetration_US_test.png

 

The difference is that the graph shows the performance against cast armor which presumably is a lot softer than the armor in the first graph.

 

In that graph we see that blunt nosed shell penetrates ~122mm against 55° armor.

Compared to the theoretical penetration of 283mm we get a slope modifier of 283 / 122 = ~2.32.

This means that the blunt shell actually doesn't have any increase in slope performance compared to the regular sharp nosed shell.

Against 45° the shell penetrate around 150mm which means a slope modifier of ~1.88 compared to the 1.80 of 90mm T33 AP. Again no improvement.

 

Whats odd about the graph is the performance of the shell against flat armor.

While the AP shell should in theory penetrate 283mm and in reality around 210mm, the blunt shell only penetrates around 177mm of armor in protection criteria and cast armor so maybe around 170mm at best.

While we can expect lower performance of the blunt shell compared to AP there's not any visible decrease or increase in performance at lower velocity.

In fact the the graph hardly changes its gradient at all.

At 2000fps, where shell shattering shouldn't occur, the blunt shell penetrates 120mm of armor while the sharp shell should penetrate ~163mm.

A 35% decrease in penetration but at ~2950fps the difference is ~60% without taking the difference in Protection and Navy criteria into account.

At 1500fps the difference is only ~18%.

 

So apperently flat nosed shells are not affected by shell shattering but their performance scales poorly against soft armor.

Which makes sense if we consider that a sharp nose pushes the armor out of the way while the flat nosed shell has to work against the entire armor.

 

Lets see how the blunt shell performs against hard armor. (122mm BR-471B)

Compared to the 90mm T33 AP the 122mm AP shell should theoretically penetrate 269mm armor with 800m/s (compared to realistic ~200mm).

Against 55° armor the shell penetrates ~108mm armor which compared to 269mm is a slope modifier of ~2.50. Thats far worse than the modifier for regular AP.

Against flat armor the shell penetrates ~205mm of armor which is ~31% worse than the theoretical AP performance.

The blunt 100mm shell penetrates roughly ~53% less than AP against soft cast armor at the same velocity.

So as expected does the blunt shell perform better against hard flat armor compared to soft armor, while on the other hand the performance at high obliquity is worse.

Also the performance rapidly decreases with lower velocity.

 

 

Conclusion:

So the only advantag Soviet blunt nosed APBC shells have over regular AP is that they have a ballistic cap that makes them lose less energy over distance.

The other advantage would be the ability to penetrate very hard armor easier than sharp nosed shells but since we don't have any difference between soft,

hard and high hardness RHA armor in the game this is pretty neglectable.

Other than that they should have far worse performance against flat armor while against high obliquity armor they shouldn't outperform sharp nosed AP but be on par at best.

Theres a reason why no other nations used flat noses on their projectiles and why even the USSR started to use APCBC instead of APBC for their post war tanks and the only reason they got used in the first place is because they are cheap and quick to produce and also happen to have similiar performance against German face hardened armor.

 

The estimated performance of Soviet blunt nosed shells compared to their AP performance based on the graph for the 100mm BR-412B shell would therefore be:

 

Numbers in brackets are theoretical AP performance based on 90mm T33 AP.

45mm AP (94mm) APBC -> 61mm. Matches in-game performance

76mm L11 AP (115mm) APBC -> 84mm. In-game: 73mm

76mm F34 AP (128mm) APBC -> 92mm. In-game: 80mm

85mm AP (191mm) APBC -> 125mm. In-game: 142mm

100mm AP (283mm) APBC -> 177mm. In-game: 215mm

122mm AP (269mm) APBC -> 176mm. In-game: 207mm

152mm AP (228mm) APBC -> 168mm. In-game: 150mm

 

We actually get the opposite result as WW2 Ballistic which assumed that at lower velocity the blunt nosed shell would penetrate less armor.

 

Update:

04.08.2018

On 04/08/2018 at 11:37, KillaKiwi said:

Curiously: I estimated the performance of the 85mm APBC based on the 90mm AP performance and the 0° modifier for AP vs APBC and got 125mm. Since that value is against cast armor and protection criteria, the actual value can be expected to be lower ->

post-278759-0-99245300-1414823490.jpg

147mm penetration for the 85mm APCBC is what we can expect from an APC shell compared to the theoretical AP performance -> around 20-30% less penetration.

The APBC performance also seems realistic 119mm vs 125mm. The only problem is the performance of AP. While the 100m performance is actually realistic due to APs tendancy to shatter against thick armor, even easier when its APHE, the performance at range doesn't match which shows us that they only took the penetration values from 100m and the rest of the table is calculated with DeMarre.

It also appears that these penetration tables were not performed vs FHA but RHA armor which again makes it seem that we can directy compare Soviet and US penetration data.

The 30° values for all shells are around 22% lower than 0° performance which is far too convienent to be true. So it appears the performance vs 30° is also estimated with a set slope modifier.

 

So if we consider that the actual values are around 5% lower than calculated we get:

45mm AP (94mm) APBC -> 58mm -> German penetration data according to WW2 Ballistic was 57mm.

76mm L11 AP (115mm) APBC -> 80mm. This matches with the estimation from a German Source about the performance of the ZIS-3 gun. (See appendix 1)

76mm F34 AP (127mm) APBC -> 87mm. This matches (2% difference) with the estimation from a German Source about the performance of the ZIS-3 gun. (See appendix 1)

85mm AP (191mm) APBC -> 119mm. This is the basis for comparison: 125 / 119 ~ 1.05 which will be subtraced to match Soviet values and to account for cast armor and Protection- vs Navy-criteria

100mm AP (282mm) APBC -> 169mm. The US test showed 177mm penetration against cast armor and Protection criteria.

122mm AP (247mm with 780m/s) APBC -> 159mm. Matches with DDR penetration data. (See appendix 2)

152mm AP (220) APBC -> 155mm. This is at least close to the in-game penetration.

 

Compared to my orginal estimation against cast armor and protection criteria: (Note I changed some AP values due to the use of different velocities or shell weight)

 

As we can see we can actually directly compare the Soviet penetration performance at 100m and 0° to US shells since it matches US Navy criteria.

So instead of using the wrong estimated performance of the shells from WW2 Ballistic we can actually use the orginal Soviet values. However the perfromance of AP shells should be quite different since those shells would still penetrate a lot of armor at low velocitiy compared to their muzzle velocity due to shattering issues.

 

One problem left is to find the correct slope modifier for the shells. From the chart we see that slope performance at 60° increases compared to vertical penetration at higher velocity. However compared to AP it scales with around the same effectivness. I used a 60° slope modifier of 2.8 for AP and the 100mm APBC round in the chart was only slightly better at both 2000fps and 2950fps. Considering that the AP performance is against RHA and Navy criteria, we could say that theres basically no difference at 60° between the APBC and AP shells. One reason why the M103 fires regular AP shells and hardly any tank in the world used flat nosed AP shells.

 

It's also interesting to note that the if the APBC performance of Soviet charts is the same as in US Navy criteria and AP is also considered to be correct, then the 122mm AP shell could only penetrate around 160mm of flat armor and would be incapable of penetrating the turret of the Tiger II H. Considering that the Tiger II was built to negate any Russian weapons of the time, this assumption might actually be correct.

 

Soviets generally produced flat nosed shells since they are a lot easier to produce as sharp AP shells due to the extra effort of hardening the nose. In same cases, like the T-34-85 they switched from flat nose to sharp nose shell production while the 122mm guns used regular sharp nosed AP. If the performance of the 122mm AP shell was so poor against thick armor it would explain why they later switched to flat nose shells. Since the BR-471B had basically the same performance as the more expensieve BR-471 shell there was no disadvantage of using the flat nosed shell.

 

Appendix:

1.)

Performance of the 76.2mm BR-354A from German source according to Soviet data when fired at 662m/s from the ZIS-3 cannon:

image.png.e4385715d55b50b84d3c39e94ba6dd

If we use the same slope modifier as they used for the 85mm guns (1.22) we get 89mm at 100m and DeMarre gets us 80mm for 615m/s.

 

 

2.)

 

DDR penetration table for the 122mm BR-412B fired at 780mm -> 160mm penetration at 100m

  Reveal hidden contents

dsc03251-jpg.76339

 

 

 

Update:

05.10.2018

 

On 05/10/2018 at 23:59, KillaKiwi said:

Ok guys, I finally figurd it out.

 

The perfect formula to calculate the 0° penetration of Soviet flat nosed AP shells.....

It so obvious but yet so absurd that you wouldn't think about it.

 

From the US penetration data of the 100mm flat nosed BR-412B and also actual Soviet data of the 85mm BR-365 we can see that the shell needs four times the energy to penetrate two times the armor.

I was trying to figure out a formula using kinetic energy which didn't give realistic results.

Then suddendly I realized why flat shells need so much energy to penetrate armor.

They don't penetrate the armor by kinetic energy but instead they use momentum.

 

So instead of

KE = 1/2 * m * v²

the penetration is influenced by

p = m * v.

 

Which makes sense if you think about it. Flat shells are comparable to billiard balls. If one ball hits the other, since both have the same weight, the ball hit will start to move with the velocity of the ball that hit it while the other will completely halt. If we change the moving ball for a ball with half the weight or it's moving with half the speed than before, the other ball will also only move with half the speed.

In terms of armor this means that we need double the mass or double the speed to penetrate double the armor.

Here we see why flat shells are very good for low velocity shells. You don't need KE to penetrate the armor, in fact it's better to fire a very heavy shell a at low velocity than a light shell at high velocity.

The problem is that bigger shells also have a bigger area which negates a lot of the increase in mass.

 

Anyway the formula for Soviet flat nosed shells 0° penetration derived from the US 100mm BR-412B data is:

 

s = p / (A * d²) where

p = m * v (the momentum)

A = ~79 (the armor resistance factor, in this case it was against US cast armor against protection under protection criteria so the calculated values should be higher than against RHA)

d = shell diamter in dm (100mm = 1.0)

 

Therefore the absulute 100% (actually 95%) correct penetration data for Soviet APBC rounds:

 

45mm BR-240 (1.43kg, 757m/s) -> 67.6mm at 0m (a lot higher than expected, the shell probably shatters due to its large HE cavity and only penetrates around 60mm)

 

76mm L11 BR-350A (6.3kg, 615m/s) -> 85mm at 0m (Same here, the BR-350A is a pretty bad design so it will probably shatter rather quickly)

 

76mm F34 BR-350A (6.3kg, 662m/s) -> 91mm at 0m (Again, the shell probably fails due to it's bad design)

 

76mm F34 BR-350B (6.55kg, 655m/s) -> 94mm at 0m (What we can expect from the shell)

 

85mm BR-385A (9.2kg, 792m/s) -> 128mm at 0m (What we can expect from the shell)

 

85mm BR-385A (9.2kg, 698m/s) -> 113mm at 1000m

 

100mm BR-412B (15.88kg, 895m/s) -> 180mm at 0m

 

107mm B-420 (18.86kg, 830m/s) -> 173mm at 0m

 

122mm BR-471B (25kg, 781m/s) ->  166mm at 0m

 

122mm BR-471B (25kg, 743m/s) ->  158mm at 500m

 

122mm BR-471B (25kg, 800m/s (A-19) -> 170mm at 0m

 

152mm BR-540B (46.5?, 600m/s) -> 153mm

 

152mm BR-540B (49kg?, 600m/s) -> 161mm

 

The data generally matches with Soviet IP penetration values which are around 10% higher than CP values which means the actual values might be up to 5% lower.

http://english.battlefield.ru/tank-armament/79-specification-and-armor-penetration.html

 

The data for the 122mm BR-471B is also very similiar to the values from the East-German manual:

  Reveal hidden contents

dsc03251-jpg.76339

Considering that my values are all slightly too high they match with the 100m data. The rest of the table appears to be calculated with De Marre.

So they tested the round at 100m got and 160mm of penetration and then calculated the rest of the table. However they did not consider that flat nosed AP shells behave differently than sharp nosed shells. So while the shell has very poor performance of around 160mm, the performance at range is actually better than in the firing table since the shell doesn't lose as much momentrum as it does kinetic energy.

 

The data against sloped armor is not easily calculated. The armor modifier changes depending on velocity and appears to decrease with increasing velocity.

Again showing how flat and slope armor penetration are complete opposite.

While flat nosed are more effective against flat armor at low velocity since slow but heavy shells can still pen a lot of armor, the opposite happends against sloped armor where high velocity is needed for better performance.

 

 

 

Update: 24.08.2019

 

I've adjusted the formula for flat armor penetration by reducing the impact of diamter on the results from power 2 to 1.8.

 

With that I get the following penetration values at 100m against flat armor:

 

56mm for the 45mm APBC

87mm for the 76mm APBC (BR-350B)

105mm for the 57mm APBC

121mm for the 85mm APBC

177mm for 100mm APBC (unchanged)

169mm for 122mm APBC (781m/s)

163mm for 152mm APBC

 

Calibers below 100mm got their penetration decreased while larger calibers now have slightly more penetration.

This generally matches with most penetration data for the 45/76/85mm guns.

 

Edited by KillaKiwi
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WT has no interest in making corrections based on historical specs.  They have transitioned to a "balance" philosphy in this game.  And if it's a nerf of their precious Soviet equipment, it ain't gonna happen, no matter what documentation you give them.  You could have a sworn statement from Zhukov, it wouldn't matter one frickin bit.  They are not gonna nerf Soviet platforms to make them look bad or embarrass the Russian Army....

 

It occurs to me that Soviet Armor in every major war where it's been deployed since 1960 has been annihilated by NATO or Israeli armor or a bunch of Afghan's with hand held AT missiles.  Not a great track record for "stalinium" in the real world....no wonder WT needs Russian bias.....it would be one sided in favor of NATO and Israeli equipment without it....

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53 minutes ago, aircavcoldsteel said:

It occurs to me that Soviet Armor in every major war where it's been deployed since 1960 has been annihilated by NATO or Israeli armor or a bunch of Afghan's with hand held AT missiles.  Not a great track record for "stalinium" in the real world....no wonder WT needs Russian bias.....it would be one sided in favor of NATO and Israeli equipment without it....

 

That sounds like a discussion for another thread. There are a lot of factors that go into that, and discussing it here would seriously derail the thread.

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So soviets have:

Advantage in BRs

Advantage in penetrations and damage.

Advantage in MM thanks to no restrictions like Germans.

 

Russian bias is a myth...

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23 minutes ago, Jagd27 said:

So soviets have:

Advantage in BRs

Advantage in penetrations and damage.

Advantage in MM thanks to no restrictions like Germans.

 

Russian bias is a myth...

well to be fair, they just used what WW2 Ballistic said to be the most realistic performance.

 

Some gameplay mechanic used to favour Soviet tanks but thats just because they seem somewhat reasonable.

Shell bouncing at sloped armor? Soviet tanks use a lot of sloped armor.

APHE being super lethal? Soviet tanks use APHE all the time.

 

Shells randomly bouncing is still a bad gameplay mechanic and APHE damage is still over the top but we can still hope for some changes.

Gajins philiospy is never change a running system.

With War Thunder this means as long as the game is enjoyable for the majority of players, don't make any global changes.

 

Currently APDS sucks damage wise but if it did the same damage as it did at the beginning it would completely change the meta and HEAT-FS would be somewhat pointless.

A lot of APCR and APDS rounds are also underperforming in penetration but you can't change one round without adjusting every other round.

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Recently my interest has been drawn again to this issue. I want to know what Russian documents tell us about sloped performance. I'll be using BR-412 and BR-412B as an example.

 

 

Data was retrieved from official shooting tables of 100-мм полевой пушки обр. 1944 г. (БС-3) and Отечественные бронированные машины 1945—1965 гг.

 

One can safely conclude that the APHEBC round is already overperforming by quite a lot at small angles. However, normal APHE is slightly underperforming.

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I agree, I don't know how Rexford and Livingston misinterpreted those graphs so badly.  I don't have much on the Russian 100mm AP, but I don't have the translated firing tables. 

Spoiler

image.thumb.png.0b2b3bf2ef87156029856369image.thumb.png.5b76bc4a1d31fa52b28d3fe0image.thumb.png.1a983ffd072717f8d43d7371image.thumb.png.091faad325e9670b25da6b74

 

As far as the 100mm APBC shell goes.  Remember that the graph being against cast armor.  At the normal/Vertical the armor would resist the same as RHA of the same thickness.  But as the angle increases with cast armor, it becomes less effective than RHA.  Though against APBC its hard to say by how much. 

6 minutes ago, LordMustang said:

Recently my interest has been drawn again to this issue. I want to know what Russian documents tell us about sloped performance. I'll be using BR-412 and BR-412B as an example.

 

https://docs.google.com/spreadsheets/d/e/2PACX-1vS3o3LsFj7IoCBAbkq9WmpB-75MuGXXJhtV2WyJ4kSLXKJUyetDTeNiaypBd5rxeKXNqNpTPm3re0Wc/pubhtml

 

Data was retrieved from official shooting tables of 100-мм полевой пушки обр. 1944 г. (БС-3) and Отечественные бронированные машины 1945—1965 гг.

 

Once can safely conclude that the APHEBC round is already overperforming by quite a lot at small angles. However, normal APHE is slightly underperforming.

 

The slope modifiers for AP are messed up by a lot in game, even at 30degree's, not even going to mention how badly at higher angles. 

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22 minutes ago, LordMustang said:

Recently my interest has been drawn again to this issue. I want to know what Russian documents tell us about sloped performance. I'll be using BR-412 and BR-412B as an example.

 

 

Data was retrieved from official shooting tables of 100-мм полевой пушки обр. 1944 г. (БС-3) and Отечественные бронированные машины 1945—1965 гг.

 

Once can safely conclude that the APHEBC round is already overperforming by quite a lot at small angles. However, normal APHE is slightly underperforming.

One problem is that we don't have any Soviet data on the performance of their shells beyond 30°.

From the performance of their AP shells it also appears as if they've calculated the penetration at range based on the penetration at 0 or 100m.

Since those AP shells should have vastly higher performance which is only reduced by the shall shattering.

 

I've calculated the performance drop for the BR-412 with a ballistic factor of 2800 and it matches. If the shell penetrates 155mm at 500m it should penetrate 135mm at 1000m.

But since the shell should be able to penetrate a lot more at 500m energy wise. It doesn't make sense that the chart doesn't show any weird performance drops which would be expected due to shattering.

From German and US papers it also appears that at 30° is the angle at which shattering occurs most frequent and generally AP shells shatter at that angle when they reach velocity around 600-610m/s and penetrate roughly their calibre thickness.

But the 30° performance matches the ballistics and also the 0° performance despite the shell being fired at 895m/s and still having 811m/s at 500m.

 

So I really doubt we can trust the performance for those Soviet tables with AP and APBC since they calculated the tables and didn't consider the performance loss due to shattering.

On the other hand the tables for APCBC should be pretty realistic since APCBC usually doesn't shatter as easily.

This can be seen in the table DDR table for the 85mm shells:

post-278759-0-99245300-1414823490.jpg

Here the APCBC shell performs as expected.

The data for the AP shot shows only 119mm while compared to US 90mm AP the shell should penetrate 191mm.

The APCBC penetrates 147mm which is around 30% less then what AP could do energy wise. If we lower the 191mm AP performance since the shell is actually APHE then the difference between AP and APC becomes even less. Since capped shells lose around 20-25% penetration compared to uncapped shells, this proofs my theory that Soviet and DDR data is only based on the 0 or 100m penetration values and the rest is calculated using De Marre and their ballistic data.

 

So a certain bug report about the performance of the Soviet 100mm BR-412D APCBC shot seems like it should get approved :)

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47 minutes ago, KillaKiwi said:

From the performance of their AP shells it also appears as if they've calculated the penetration at range based on the penetration at 0 or 100m.

 Since those AP shells should have vastly higher performance which is only reduced by the shall shattering.

I somehow doubt that the Soviets would miscalculate values for something they have to rely on themselves for quite a few years. Even though the numbers are rounded to 5mm, I'm still inclined to believe that a shooting table is based on testing. I would rather believe the people that actually used this gun than some calculation based on a book which contains many errors, researched by foreigners.

 

Also, as far as I know Soviets used a 75% penetration probability and different testing conditions, which still seems stricter than the Navy standard, especially when comparing known penetration values to Soviet testing documents.

 

I've already forwarded several documents on BR-412D to the developers. I'll have to wait now and see what they find out.

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1 hour ago, LordMustang said:

I somehow doubt that the Soviets would miscalculate values for something they have to rely on themselves for quite a few years. Even though the numbers are rounded to 5mm, I'm still inclined to believe that a shooting table is based on testing

Nah most of their values were calculated according to WW2 Ballistics and the table from The Russian Battlefield site. I imagine they either completely calculated the performance or just calculated the range performance based on the penetration at 100m.

The Germans weren't much better. They use penetration data for 30° and applied them against tanks that were also angled 30° in their tank combat manuals.

So German manuals said that the KwK 40 couldn't penetrate the armor of the T-34 unless at 100m or the turret of an IS-1/2 unless at 100m when we know that they actually could penetrate the armor from much further. They also based their slope performance soley on the performance of the 75mm shell when in reality, heavier shells have better slope performance.

 

Honestly I don't think penetration tables had much value for armies and sometimes caused more harm then good, since people often seem to misinterpret them.

Important was that they could take out other tanks based on combat experience or testing.

We don't have any Soviet values at 60° but they should be a lot higher than what they came up with for their 0° and 30° performance, since 0° and 30° are the angles where shattering most likely occurs.

Apperently they even tested their shells against face hardened armor which would further decrease the performance for AP shells.

 

 

1 hour ago, RedWitch4 said:

Some data from British testing of the BR-412B 

Do you know where this is from and do you know if it also featured the BR-412 AP shell for comparison?

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5 hours ago, KillaKiwi said:

Nah most of their values were calculated according to WW2 Ballistics and the table from The Russian Battlefield site. I imagine they either completely calculated the performance or just calculated the range performance based on the penetration at 100m.

The Germans weren't much better. They use penetration data for 30° and applied them against tanks that were also angled 30° in their tank combat manuals.

So German manuals said that the KwK 40 couldn't penetrate the armor of the T-34 unless at 100m or the turret of an IS-1/2 unless at 100m when we know that they actually could penetrate the armor from much further. They also based their slope performance soley on the performance of the 75mm shell when in reality, heavier shells have better slope performance.

 

Honestly I don't think penetration tables had much value for armies and sometimes caused more harm then good, since people often seem to misinterpret them.

Important was that they could take out other tanks based on combat experience or testing.

We don't have any Soviet values at 60° but they should be a lot higher than what they came up with for their 0° and 30° performance, since 0° and 30° are the angles where shattering most likely occurs.

Apperently they even tested their shells against face hardened armor which would further decrease the performance for AP shells.

 

 

Do you know where this is from and do you know if it also featured the BR-412 AP shell for comparison?

 

Yes, as far as I remember, most of the Russian penetration tables are demarre calculated vs Krupp Cemented armor firing tests.  Though later after WW2, they started testing against RHA.  So rounds like BR412D were tested against RHA.  As far as the German stuff goes, it's hard to say.  Most of the claims of the 75mm kwk 40 penetrating the T-34 glacis at 1600m are anecdotal at best.  As you'd be hard pressed to find a perfectly flat field where the angle of the hull would be perfectly normal, and not tilted forwards etc.  Yugoslav tests had the Pak 40, which had a higher muzzle velocity than the Kwk40 penetrating at only 1300m, under misinterpreted US criteria under perfect conditions with pzgr39.

 

Depends on the Penetration table.  Brits considered the ballistic curve graphs in US manuals like TM 9-1907 to be on the more accurate side when it came to predicting average penetration ability.  Where the US had problems was with Solid Shot, due to heat treatment issues.

 

7 hours ago, LordMustang said:

I somehow doubt that the Soviets would miscalculate values for something they have to rely on themselves for quite a few years. Even though the numbers are rounded to 5mm, I'm still inclined to believe that a shooting table is based on testing. I would rather believe the people that actually used this gun than some calculation based on a book which contains many errors, researched by foreigners.

 

Also, as far as I know Soviets used a 75% penetration probability and different testing conditions, which still seems stricter than the Navy standard, especially when comparing known penetration values to Soviet testing documents.

 

I've already forwarded several documents on BR-412D to the developers. I'll have to wait now and see what they find out.

 

Soviet Criteria is in effect roughly between US protection Criteria and US Navy Criteria as far as what is considered a complete penetration.  Outside of that they used V80 ballistic limit standard.  They also had V20 for initial penetration testing.  Russian Criteria required the majority of a shell to pass through the plate in a good enough condition to burst.  The shell could still be lodged in the plate as long as it was at least 75% of the shell on the other side.  Russia only used Shells with HE filler outside of apcr.  With what solid shot they did use, it was pretty similar to US Navy Criteria, with the majority of the projectile having passed through the the plate even in a shattered state.

 

Ignore what WW2 ballistics says about US penetration Criteria, as the authors completely ignored half of what the manuals they were taking it from said.  US Navy Criteria, especially for AP with a bursting charge, required the entire projectile to pass through the plate.  For solid shot, which had shatter issues, the majority of the projectile mass had to pass through the plate.  Protection Criteria picks up where Navy leaves off, where a projectile must eject enough mass or spall from the hole to damage a witness plate 6in behind the target.  US used V50 ballistic limit standard. 

 

V80 means 80% of shots fired were considered complete penetrations.  V50 means 50% of shot fired were considered complete penetrations. 

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Since you're already doing a deep research on APBC, I invite you to please make a test in game and then comment the results. 

 

Apparently, in game APBC shells seem to almost ignore the angle of the armor they meet when it comes to LOS thickness. 

 

Pick a tank (I used the Italian P40 as testbed, since I use it a lot in game). First, switch to ordinary armor view in the hangar. While hovering the cursor on various spots, you'll see the fixed armor thickness value, and the LOS thickness varying according to the current perspective angle. 

 

Then, switch on "protection analysis", choose any shell OTHER than APBC, test it on an armor plate, first unangled and then angled. The indicated LOS thickness still varies accordingly. 

 

Now switch to APBC shell and repeat the same exact test: astonishingly, even at considerable angles, the indicated LOS thickness increases only by a very marginal (almost negligible) amount compared to the minimum plate thickness at 90°.

 

In game, this makes APBC shells EXTREMELY lethal since they basically ignore the armor effectiveness increase at angles, and they are apparently only affected by the ricochet limit angle. 

 

This is not only an impression of mine, and it was actually already tested, bug reported and accepted more than a year ago, yet nothing has changed since then, and the issue is supposedly even more blatant now that it can viewed with the protection analysis tool (which, unless I got it totally wrong, is supposed to rely on the same system that actually calculates impacts, penetrations and damage in battle). 

 

Edit: issue also brought up here.

 

What do you think? 

Edited by Serpiko82
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3 hours ago, Serpiko82 said:

What do you think? 

Well thats the whole problem with APBC that they use unrealistic slope modifiers from WW2 Ballistic and apperently are even better than in the book.

The way the are modelled as long as they overmatch the armor an increase in angle has only small effect on the armor effectiveness.

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On 10/07/2018 at 15:01, RedWitch4 said:

Some data from British testing of the BR-412B 

 

mdRr5O1.jpg

OYtXLjw.png

 

  Reveal hidden contents

JeeLcTO.jpg

JeeLcTO.jpg

 

 

 

 

 

 

Looking at the data I would argue that they match with the US data considering the US testing was performed in protection criteria and against cast armor.

The British data shows the round with less performance than the US data but the US tests were also less strict.

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Curiously: I estimated the performance of the 85mm APBC based on the 90mm AP performance and the 0° modifier for AP vs APBC and got 125mm. Since that value is against cast armor and protection criteria, the actual value can be expected to be lower ->

post-278759-0-99245300-1414823490.jpg

147mm penetration for the 85mm APCBC is what we can expect from an APC shell compared to the theoretical AP performance -> around 20-30% less penetration.

The APBC performance also seems realistic 119mm vs 125mm. The only problem is the performance of AP. While the 100m performance is actually realistic due to APs tendancy to shatter against thick armor, even easier when its APHE, the performance at range doesn't match which shows us that they only took the penetration values from 100m and the rest of the table is calculated with DeMarre.

It also appears that these penetration tables were not performed vs FHA but RHA armor which again makes it seem that we can directy compare Soviet and US penetration data.

The 30° values for all shells are around 22% lower than 0° performance which is far too convienent to be true. So it appears the performance vs 30° is also estimated with a set slope modifier.

 

So if we consider that the actual values are around 5% lower than calculated we get:

45mm AP (94mm) APBC -> 58mm -> German penetration data according to WW2 Ballistic was 57mm.

76mm L11 AP (115mm) APBC -> 80mm. This matches with the estimation from a German Source about the performance of the ZIS-3 gun. (See appendix 1)

76mm F34 AP (127mm) APBC -> 87mm. This matches (2% difference) with the estimation from a German Source about the performance of the ZIS-3 gun. (See appendix 1)

85mm AP (191mm) APBC -> 119mm. This is the basis for comparison: 125 / 119 ~ 1.05 which will be subtraced to match Soviet values and to account for cast armor and Protection- vs Navy-criteria

100mm AP (282mm) APBC -> 169mm. The US test showed 177mm penetration against cast armor and Protection criteria.

122mm AP (247mm with 780m/s) APBC -> 159mm. Matches with DDR penetration data. (See appendix 2)

152mm AP (220) APBC -> 155mm. This is at least close to the in-game penetration.

 

Compared to my orginal estimation against cast armor and protection criteria: (Note I changed some AP values due to the use of different velocities or shell weight)

On 09/07/2018 at 16:17, KillaKiwi said:

Numbers in brackets are theoretical AP performance based on 90mm T33 AP.

45mm AP (94mm) APBC -> 61mm. Matches in-game performance

76mm L11 AP (115mm) APBC -> 84mm. In-game: 73mm

76mm F34 AP (128mm) APBC -> 92mm. In-game: 80mm

85mm AP (191mm) APBC -> 125mm. In-game: 142mm

100mm AP (283mm) APBC -> 177mm. In-game: 215mm

122mm AP (269mm) APBC -> 176mm. In-game: 207mm

152mm AP (228mm) APBC -> 168mm. In-game: 150mm 

 

As we can see we can actually directly compare the Soviet penetration performance at 100m and 0° to US shells since it matches US Navy criteria.

So instead of using the wrong estimated performance of the shells from WW2 Ballistic we can actually use the orginal Soviet values. However the perfromance of AP shells should be quite different since those shells would still penetrate a lot of armor at low velocitiy compared to their muzzle velocity due to shattering issues.

 

One problem left is to find the correct slope modifier for the shells. From the chart we see that slope performance at 60° increases compared to vertical penetration at higher velocity. However compared to AP it scales with around the same effectivness. I used a 60° slope modifier of 2.8 for AP and the 100mm APBC round in the chart was only slightly better at both 2000fps and 2950fps. Considering that the AP performance is against RHA and Navy criteria, we could say that theres basically no difference at 60° between the APBC and AP shells. One reason why the M103 fires regular AP shells and hardly any tank in the world used flat nosed AP shells.

 

It's also interesting to note that the if the APBC performance of Soviet charts is the same as in US Navy criteria and AP is also considered to be correct, then the 122mm AP shell could only penetrate around 160mm of flat armor and would be incapable of penetrating the turret of the Tiger II H. Considering that the Tiger II was built to negate any Russian weapons of the time, this assumption might actually be correct.

 

Soviets generally produced flat nosed shells since they are a lot easier to produce as sharp AP shells due to the extra effort of hardening the nose. In same cases, like the T-34-85, they switched from flat nose to sharp nose shell production while the 122mm guns used regular sharp nosed AP. If the performance of the 122mm AP shell was so poor against thick armor it would explain why they later switched to flat nose shells. Since the BR-471B had basically the same performance as the more expensieve BR-471 shell there was no disadvantage of using the flat nosed shell.

 

Appendix:

1.)

Performance of the 76.2mm BR-354A from German source according to Soviet data when fired at 662m/s from the ZIS-3 cannon:

image.png.e4385715d55b50b84d3c39e94ba6dd

If we use the same slope modifier as they used for the 85mm guns (1.22) we get 89mm at 100m and DeMarre gets us 80mm for 615m/s.

 

 

2.)

 

DDR penetration table for the 122mm BR-412B fired at 780mm -> 160mm penetration at 100m

Spoiler

dsc03251-jpg.76339

 

 

Edited by KillaKiwi
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Looking at this chart about the US 90mm AP we can see that below 2000fps before the round experiences shatter issues against 30°, the slope modifier for 30° appears to be around 1.22.

Spoiler

BQ3OipH.jpg

This modifier is also shown for AP shells at 30° in WW2 Ballistics. So it appears that AP shells regardless of size had a slope modifier of ~1.22 at 30° as long as they didn't break or shatter.

Which explains why this modifier is also seen on the Soviet penetration charts.

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On 04/08/2018 at 11:37, KillaKiwi said:

image.png.e4385715d55b50b84d3c39e94ba6dd

Thats actually the table for the special BR-350A fired at 745m/s.

So the penetration should be 150mm for such an AP shell but realistically a lot lower due to lower nose hardness and large HE filler.

Reduced by APBC performance we get around 103mm at point blank range.

If the shell however penetrated around 15% less compared to the US 90mm then the AP would penetrate 130mm and the APBC 90mm which matches the soviet data if the 30° value was calculated fromt the 0° with a 1.23 slope modifier.

The performance might be slightly worse since the BR-350A was not a good design, even for an APBC round.

Edited by KillaKiwi
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Unfortunately, I am unable to provide any useful data for your research right now, but I still want to say the following to you: Thank you for doing all that research. I highly respect the time and effort you and all the others put into this. 

 

Hopefully those efforts are successful. I keep my fingers crossed.

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This information also emphasises the correctness of the US Test with BR-412B

http://tankarchives.blogspot.com/2017/06/soviets-vs-m48-patton.html

(-> http://btvt.info/5library/vbtt_1958_02_m48.htm)

patton-3.jpg

 

2: Satisfactory penetration limit of the upper front hull with blunt tipped shells.

 

So the shells needs around ~910m/s to completely penetrate the 110mm cast armor sloped at 60°.

The US documents shows that it penetrates ~4.33" (110mm) of cast armor with around 900m/s under protection criteria.

 

Pretty close match. Which again shows how the penetration in the game is completely wrong when it comes to vertical and slope penetrations.

 

I belive the 1) in the pictures shows the BR-412D APCBC shell. It requires around 1000m/s to penetrate the 110mm at 60°, showcasing the inferior performance of APC shells against sloped armor.

This performance is similiar to the 105mm APC shell fired by the 105 Tiger II which would result in around 280mm penetration with a slope modifier of 2.55 for 60° and the correct performance of the shell is somehwere between 260-280mm.

 

Edited by KillaKiwi
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On 09/07/2018 at 17:44, muzzleflash98 said:

 

That sounds like a discussion for another thread. There are a lot of factors that go into that, and discussing it here would seriously derail the thread.

But those are trained crews not rookies that get taken out

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On 10/07/2018 at 13:17, LordMustang said:

Recently my interest has been drawn again to this issue. I want to know what Russian documents tell us about sloped performance. I'll be using BR-412 and BR-412B as an example.

 

 

Data was retrieved from official shooting tables of 100-мм полевой пушки обр. 1944 г. (БС-3) and Отечественные бронированные машины 1945—1965 гг.

 

One can safely conclude that the APHEBC round is already overperforming by quite a lot at small angles. However, normal APHE is slightly underperforming.

Bias? What bias? No bias in here, move along sir :)

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On 04/08/2018 at 11:37, KillaKiwi said:

45mm AP (94mm) APBC -> 58mm -> German penetration data according to WW2 Ballistic was 57mm.

76mm L11 AP (115mm) APBC -> 80mm. This matches with the estimation from a German Source about the performance of the ZIS-3 gun. (See appendix 1)

76mm F34 AP (127mm) APBC -> 87mm. This matches (2% difference) with the estimation from a German Source about the performance of the ZIS-3 gun. (See appendix 1)

85mm AP (191mm) APBC -> 119mm. This is the basis for comparison: 125 / 119 ~ 1.05 which will be subtraced to match Soviet values and to account for cast armor and Protection- vs Navy-criteria

100mm AP (282mm) APBC -> 169mm. The US test showed 177mm penetration against cast armor and Protection criteria.

122mm AP (247mm with 780m/s) APBC -> 159mm. Matches with DDR penetration data. (See appendix 2)

152mm AP (220) APBC -> 155mm. This is at least close to the in-game penetration.

 

The problem with these estimation is that it's based on the AP performance of the 100mm shell vs the APBC penetration.

However after some comparison with US AP shells I established that the penetration of AP shells that shatter against thick armor is very similiar to the values of the flat BR-412B shell when considering the Mass/Area. Which makes sense. If the AP shell shatters against thick armor it will penetrate the armor by force alone and the expected penetration would be similiar to flat nosed shells.

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4 hours ago, KillaKiwi said:

 

The problem with these estimation is that it's based on the AP performance of the 100mm shell vs the APBC penetration.

However after some comparison with US AP shells I established that the penetration of AP shells that shatter against thick armor is very similiar to the values of the flat BR-412B shell when considering the Mass/Area. Which makes sense. If the AP shell shatters against thick armor it will penetrate the armor by force alone and the expected penetration would be similiar to flat nosed shells.

The the thing is in real life if a shell hits armour and it's not very thick it'll tear it but the game doesn't replicate that so we end up with hit marker instead

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