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Definitive answer to the "Blunt shells vs Sloped armour" question.


Good day everyone. There is an idea floating among armored vehicle enthusiasts, that the soviet-style blunt headed AP shells are supposedly more efficient in defeating sloped targets. Until now there has been a lot of circumstantial evidence against it, but only recently I was able to get my hands on two pieces of data that, when analyzed side by side, prove this to be wrong once and for all.

First are the records of ballistic testing of captured soviet 100mm BR-412B shells by the british. Here we can see the shell's performance in a controlled environment, where one doesn't have to wonder about what the striking velocity was at the given distance or whether the piece of armor penetrated had any manufacturing flaws (no "late war german steel bad" excuse this time).

 

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Second is the collection of ballistic limits of several similar models of sharp tipped, uncapped, AP shells taken from this document here. This is the source I've chosen over the multitude of others, because it reports the US army ballistic limit and lists other helpful variables.

 

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Finally, distilling all the data into a more readable form yields this table here:

 

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As you can see, neither type of shell has a definitive advantage.

I hope this was enough to convince those of you who still had any doubts about this matter. Thank you for your attention, fellow tankers. :salute:  See ya on the battlefield.

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As a matter of fact, theres a document about the 105mm T182 shell and how this shell performs.

This experimental shell, actually three,  was made from T32 APCBC shells which had their penetration cap removed.

Shell C had it's nose cut off, making it basically blunt.

However the penetration test against a 127mm plate sloped at 55° showed that the shell had basically the same performance as the shell with an intact nose.

Even slightly worse, probably because the shell was now lighter with part of its nose cut off.

 

https://archive.org/details/DTIC_AD0390746/page/n9

 

Conclusion:

It makes no difference, if the shell is flat or has a sharp nose when striking sloped armor (>45°). Infact it doesn't even matter if the shell is heat treated. It will defeat the plate by deforming it via it's own kinetic energy until the plate ruptures. The nose will however increase penetration against near vertical armor.

 

Since the armor defeating mechanism of a blunt and sharp shells are so different against 0° armor, we can't use slope modifiers to determine the slope defeating power of a shell.

Edited by KillaKiwi
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29 minutes ago, KillaKiwi said:

Conclusion:

It makes no difference, if the shell is flat or has a sharp nose when striking armor. Infact it doesn't even matter if the shell is heat treated. It will defeat the plate by deforming it via it's own kinetic energy until the plate ruptures

 

Since the armor defeating mechanism of a blunt and sharp shells are so different against 0° armor, we can't use slope modifiers to determine the slope defeating power of a shell.

 

Thanks - needed this simplified language version!! :lol2::good:

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4 minutes ago, KillaKiwi said:

As a matter of fact, theres a document about the 105mm T182 shell and how this shell performs.

This experimental shell, actually three,  was made from T32 APCBC shells which had their penetration cap removed.

Shell C had it's nose cut off, making it basically blunt.

However the penetration test against a 127mm plate sloped at 55° showed that the shell had basically the same performance as the shell with an intact nose.

Even slightly worse, probably because the shell was now lighter with part of its nose cut off.

 

https://archive.org/details/DTIC_AD0390746/page/n9

 

Conclusion:

It makes no difference, if the shell is flat or has a sharp nose when striking armor. Infact it doesn't even matter if the shell is heat treated. It will defeat the plate by deforming it via it's own kinetic energy until the plate ruptures

 

Since the armor defeating mechanism of a blunt and sharp shells are so different against 0° armor, we can't use slope modifiers to determine the slope defeating power of a shell.

 

First: great find @KillaKiwi I will examine this document later in detail. 

 

Second: let's not jump to conclusions. if "it doesn't even matter if the shell is heat treated" why those poor fools who were designing them even bothered then, hmmm?

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6 minutes ago, Peasant_wb said:

Second: let's not jump to conclusions. if "it doesn't even matter if the shell is heat treated" why those poor fools who were designing them even bothered then, hmmm?

Well I was talking about sloped armor which isn't pierced using a high hardened shell nose. I probably should have been more specific on that matter.

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25 minutes ago, KillaKiwi said:

Well I was talking about sloped armor which isn't pierced using a high hardened shell nose. I probably should have been more specific on that matter.

I thought as much. But not everybody would. I know I'd hate to have my words misinterpreted, so I'm trying to be as specific as I can, most of the times. It's something that most people find annoying in real life conversations with me. :D

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There are more ballistic limits for T33 at high angle from a few documents.  

 

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  • 1 month later...

@KillaKiwi I've transferred most of the table @Conraire posted onto an Excel sheet. After examining it in detail I have found a pattern in the data. Under conditions where the projectile suffers a complete breakup (high striking velocities against thick plates of adequate hardness at significant obliquity) the ballistic limits can be calculated by altering the classical DeMarre's function through giving the cosine function the exponent of 0,592 (fitted through least squares method) with K = 2300. The new formula can predict the ballistic limits(Army) fairly closely at those conditions. Link to the sheet.

 

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The results are in very good agreement with live testing data that I have at my disposal, like that of the soviet 100mm and 122mm guns against Panthers and british tests with 6pdr and 17pdr AP/APC against the Panther/Tiger I. Panther tanks with 80mm glacis show the effective thickness around 75mm from several independent tests, confirming the decision to increase the thickness to 85mm to bring the protection level up to spec.

 

It's also indirectly supported by other facts, like the T-70 glacis (35mm/60°) is estimated to be just enough to be immune to the german 5cm L/42 gun and the KV-1S 40mm/65° glacis plate against the more powerful 5cm L/60. These are unlikely to be just coincidences.

Edited by Peasant_wb

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On 05/11/2019 at 21:02, Peasant_wb said:

Link to the sheet.

So the sheet gives armor penetration values for projectiles which breakup during penetration?

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1 minute ago, KillaKiwi said:

So the sheet gives armor penetration values for projectiles which breakup during penetration?

 

Yes. Well, not just any projectile. Specifically steel(not tungsten) uncapped projectiles, both sharp tipped and soviet blunt headed shells. It might work for other types as well, but I cant guarantee it, no harm in trying though. 

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  • 9 months later...

All of that is very interesting but it omits one cool fact. IS2 tanks were UPGRADED to blunt ammo during their career.

Sharp 122mm could penetrate panther's UFP at ~1-1.5 km and often gave ricochet even if armor was terribly damaged.

Blunt 122mm could penetrate panther's UFP at 2.5 km and did not give ricochet.

Blunt ammo has superior slope modifiers and ricochet performance.

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This is all very interesting, has a bug-report / suggestion already been made?

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11 hours ago, Max__Damage said:

All of that is very interesting but it omits one cool fact. IS2 tanks were UPGRADED to blunt ammo during their career.

Sharp 122mm could penetrate panther's UFP at ~1-1.5 km and often gave ricochet even if armor was terribly damaged.

Blunt 122mm could penetrate panther's UFP at 2.5 km and did not give ricochet.

Blunt ammo has superior slope modifiers and ricochet performance.

 

??

 

I thought the initial 122mm ammo is the BR471 and 471B - which are blunt, and it is the post-war BR471D that is sharp - so the "upgrade" is from blunt to sharp - not sharp to blunt as you suggest?

 

Overview] Russian Anti-Tank Ammunition - General & Upcoming - War ...

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8 hours ago, Josephs_Piano said:

 

??

 

I thought the initial 122mm ammo is the BR471 and 471B - which are blunt, and it is the post-war BR471D that is sharp - so the "upgrade" is from blunt to sharp - not sharp to blunt as you suggest?

 

Overview] Russian Anti-Tank Ammunition - General & Upcoming - War ...

Nonono In game and in reality there were at least 3 ammo types:

the first one (default) is sharp

the second one (wartime upgrade) is blunt

and the last one APCBC capped is a post war invention which in the game can be seen on IS3 tanks.

 

The reason to upgrade to blunt ammo was exactly to improve slope performance as i indicated above.

 

In game it works pretty realistically: the default sharp ammo stops penetrating panther at ~1000m. blunt ammo up to 2500.

Edited by Max__Damage
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On ‎25‎/‎08‎/‎2020 at 07:07, Max__Damage said:

All of that is very interesting but it omits one cool fact. IS2 tanks were UPGRADED to blunt ammo during their career.

Sharp 122mm could penetrate panther's UFP at ~1-1.5 km and often gave ricochet even if armor was terribly damaged.

Blunt 122mm could penetrate panther's UFP at 2.5 km and did not give ricochet.

Blunt ammo has superior slope modifiers and ricochet performance.

 

A necropost citing incorrect figures & a post war round.....


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Edited by Chomusuke1

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8 hours ago, Chomusuke1 said:

A necropost citing incorrect figures & a post war round.....
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Nothing wrong with my information though. The blunt round was developed september 1944 and issued spring 1945 so it is a 100% wartime round. Post war round is BR471D.

When german armor quality plummeted the sharp round indeed was more then enough for a Panther because the armor was too brittle. Whatever we have in game has perfect armor quality and can be penetrated at ~900m only and can be referred to as a theoretical limit. Early instances of Panther tanks are known to sometimes deflect 122mm sharp ammo even if armor suffered critical damage as a result.

Edited by Max__Damage
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New information has come to my knowledge since I've made this post.

 

From the book "Танковая мощь СССР часть III Золотой век":

 

x9jwkLA.jpg

 

Translation:

Quote

The ballistic trials on fully kitted samples of captured tanks with an IS-122 tank, from serial production batch, were conducted on the UZTM's firing range in January of 1944 and have demonstrated that the service 122mm shell reliably defeats the frontal armour of the "Panther" tank at range of 600-700m, while the improved armour piercing tracer shell with high explosive filler (manufactured from schematic No.2-2868 A) could do it from 1200-1400m, which is why on 15 of January NKB proceeded to setting up production facilities for this type of shell.

 

A report titled "Conclusions about fighting and technical qualities of ISU-122 SPGs and IS-2 heavy tanks." sent 15th of March 1945 to the commander of armored and mechanized forces of the 1st Ukrainian front general-colonel Nikolai Novikov says, among other things:

Quote

"ИСУ-122 и ИС-122 обладают мощной артиллерийской системой, которая на дистанции 1300 метров пробивает броню танков "Тигр" и "Пантера" противника. При стрельбе по танку типа "Пантера" с дистанции 2000 метров в лоб бронебойный снаряд рикошетирует, не пробивая брони. Меткость стрельбы хорошая. Пушка, действуя с дистанции 1500 - 2000 метров, имеет весьма незначительное рассеивание и может уничтожать все огневые точки."

 

Translation:

Quote

"ISU-152 and IS-122 posses a powerful weaponry which at a distance of 1300m penetrates armour of the enemy "Tiger" and "Panther" tanks. When fired upon a "Panther" tank from a distance of 2000m from the front the armor piercing shell ricochets without holing the armor. Accuracy is good. Gun firing from distances of 1500-2000m has a negligible dispersion and can destroy any fortification."

 

Page itself:

Spoiler

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On 25/08/2020 at 04:07, Max__Damage said:

All of that is very interesting but it omits one cool fact. IS2 tanks were UPGRADED to blunt ammo during their career.

Sharp 122mm could penetrate panther's UFP at ~1-1.5 km and often gave ricochet even if armor was terribly damaged.

Blunt 122mm could penetrate panther's UFP at 2.5 km and did not give ricochet.

Blunt ammo has superior slope modifiers and ricochet performance.

 

My understanding is the Soviets started manufacturing blunt nose AP rounds to deal with the steel quality or hardness not being very high, so the sharp nose rounds tended to shatter. The blunt nose help to eliminate this issue. US sharp nose AP had similar issues but those issues were resolved with better quality steel and heat treatment. 

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On 25/08/2020 at 13:07, Max__Damage said:

All of that is very interesting but it omits one cool fact. IS2 tanks were UPGRADED to blunt ammo during their career.

Sharp 122mm could penetrate panther's UFP at ~1-1.5 km and often gave ricochet even if armor was terribly damaged.

Blunt 122mm could penetrate panther's UFP at 2.5 km and did not give ricochet.

Blunt ammo has superior slope modifiers and ricochet performance.

The difference, that made the blunt shell BR-471B superior at range, was that it was ballistic capped, making the shell more aerodynamic and lose less velocity at range.

 

During WW2 the firing table for the 122mm gun and ammunition was wrong, hence the Soviets concluded that they shells would defeat the Panther at ~1200m and +2500m, when in reality the range was more around 700-800m and 1200-1400m as stated by Peasant:

 

https://forum.warthunder.com/index.php?/topic/463549-definitive-answer-to-the-blunt-shells-vs-sloped-armour-question/&do=findComment&comment=8637246

 

On 27/08/2020 at 22:36, Peasant_wb said:

Translation:

Quote

The ballistic trials on fully kitted samples of captured tanks with an IS-122 tank, from serial production batch, were conducted on the UZTM's firing range in January of 1944 and have demonstrated that the service 122mm shell reliably defeats the frontal armour of the "Panther" tank at range of 600-700m, while the improved armour piercing tracer shell with high explosive filler (manufactured from schematic No.2-2868 A) could do it from 1200-1400m, which is why on 15 of January NKB proceeded to setting up production facilities for this type of shell.

 

 

Blunt shells for 45, 57, 76 and 85mm guns were commenly used during the war, mainly because they were easier to produce than sharp tipped AP rounds.

Hence why guns with low production numbers like the 100 and 122mm still used sharp tipped AP shells as there was no need to produce these shells in large numbers.

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