122mm vs 88mm

[Laurelix]

In terms of rate of fire we already know the 88mm is much better. For example it’s better to penetrate a tank twice with an 88mm than once with 122mm gun. Likewise it’s more battle effective to shoot 2x 88mm HE shells than a single 122mm HE shell

But how does their penetration capability compare tho? The following values are not the mamby pamby values currently in War Thunder / Enlisted but reflect real life capability.

:::

KwK43 88mm L/71
PzGr.39 APCBC (10.2kg shell)
Penetration:
235mm @ 0m at 0 ° — 1000m/s
175mm @ 0m at 30 °
87mm @ 0m at 60 °

204mm @ 1000m at 0 ° — 906m/s
155mm @ 1000m at 30 °
77mm @ 1000m at 60 °

Battle Capability
• Its UNABLE able to Penetrate IS-3 Hull
• Its UNABLE to Penetrate T-44A Upper Glacis
• Can Penetrate Tiger II H turret up to 1700m
• Can Penetrate Panther Upper Glacis up to 2250m

:::

125mm D-25T L/49
BR-471 AP (25.0kg shell)
Penetration:
205mm @ 0m at 0 ° — 795m/s
160mm @ 0m at 30 °
97mm @ 0m at 60 °

160mm @ 1000m at 0 ° — 670m/s
130mm @ 1000m at 30 °
78mm @ 1000m at 60 °

Battle Capability
• Can Penetrate IS-3 hull up to 150m
• Can Penetrate T-44 Upper Glacis up to 325m
• Can Penetrate Tiger II H turret up to 400m
• Can Penetrate Panther Upper Glacis up to 1750m

[GeneralBrus]

Why would the 88 not be able to penetrate IS3 hull while the 122 can - even though the 88 has more pen?

I don’t quite follow your logic here.

[Laurelix]

The 122mm has better penetration

122mm BR-471
25.0kg Shell
0.160kg HE filler

24.84kg penetrator at 795m/s
Kinetic Energy = 0.5 x weight x velocity^2
0.5 x 24.84 x 795 x 795
= 7,849,751 Joules of Kinetic Energy

:::

88mm PzGr.39
10.2kg shell
0.292kg Windshield
0.059kg HE filler
0.585-0.820kg anti deformation cap

9.03kg-9.264kg penetrator
Kinetic Energy = 0.5 x weight x velocity^2
0.5 x 9.264 x 1000 x 1000
= 4,632,000 Joules of Kinetic Energy

[GeneralBrus]

How?

[Laurelix]

The 88mm has Anti-Deformation Cap
Hence why it’s called APCBC shell
(AP-Capped-BC)
That’s why it doesn’t deform and achieves better flat penetration.
Also the BC is just a ballistic cap, an aerodynamic windshield so the shell losses velocity slower over distance.

The 122mm does not have the Anti-Deformation Cap meaning it deforms against flat thick armour, especially against Face Hardenned Steel which amplifies the deformation effect of AP shells without anti deformation caps.
This is why APC/APCBC made the FHA armour go obselete and Germans went from FHA to RHA steel armour. The Anti Deformation Cap prevents deformation by transferring all the shock and energy away from the tip of the penetrator and spreads it out to the sides and body of the penetrator thus preventing the deformation of the sharp tip.

122mm actually defeats 253mm at 0 degrees, that’s the penetration capability of the shell but after it deforms at 0 degrees, it only achieves 205mm at 0 degrees. At high obliquities when the tip no longer strikes the steel plate first, deformation no longer occurs and behaves like a 253mm penetrating round and since it’s a 122mm round, the T/D (armour thickness to shell diameter) ratio is much better compared to 88mm when dealing with thick sloped armour plates.

It’s also the reason why the German Panzer II, Panzer III, Panzer IV’s which were using FHA armour had flat armour profiles rather than sloped armour, since sloped armour reduces the deformation effect against non capped shells.

Unfortunately… Gaijin / Darkflow has not implemented Face Hardenned Armour for tanks such as Pz.I, Pz.II, Pz.III, Pz.IV, Ha-Go, Chi-Ha, Ke-Ni. Also… 0.50 cal bullets do not have anti deformation caps, thus FHA is very effective against them.

[Laurelix]

Same scenario also occurs in this case as well

90mm M82 APCBC with smaller penetrator has 171mm @ 0m penetration but was unable to penetrate Panther Upper Plate

90mm T33 APBC with much better penetrator has only 165mm @ 0m penetration (after it deforms) and could penetrate Panther Upper Glacis up to 1100 yards.

Below is a more detailed explanation of T33 APBC vs M82 APCBC.

——

90mm M82 APC(BC)
2.8inch @ 0m at 55 ° — 2800ft/s
(71mm @ 0m at 55 ° — 853m/s)

Panther UFP = 80mm at 55 °

:::

90mm T33 AP(BC)
3.8inch @ 0m at 55 ° — 2800ft/s
(96.5mm @ 0m at 55 ° — 853m/s)

Panther UFP = 80mm at 55 °

:::

AP slope modifiers from WWII Ballistics: Armour and Gunnery

T/D ratio = 1.072
(96.5mm thick steel / 90mm shell diameter)
At 55 ° = 2.184 Slope Modifier

96.5mm at 55 ° = 210-211mm at 0 °
(96.5mm x 2.184 slope modifier)

T33 APBC has 210-211mm penetration at 0 ° before it deforms against flat thick armour due to lack of piercing cap and it deforms worse than M77 AP because it was reheat treated M77 AP with ballistic cap attached to it.

:::

M82 APCBC is rated to defeat 6.75inch (171mm) @ 0m at 0 °

It has 217mm long penetrator and penetrator is further reduced by the large HE filler cavity

T33 APBC can penetrate 210-211mm @ 0m at 0 ° before the shell deforms against flat thick armour due to lack of piercing cap but it shouldn’t be surprising that it’s better than M82 APCBC

It features bigger penetrator with length of 250mm and has no HE filler that reduces the penetrator size like it does on M82 APCBC.

The T33 APBC with bigger penetrator and thus greater kinetic energy achieved 210-211mm penetration (165mm post deformation) at 0 ° compared to 171mm penetration of M82 APCBC with smaller penetrator.

According to the British… their 2 Pounder AP, 40mm round, 1.08kg penetrator at 2600ft/s (792m/s) could penetrate 90mm of Armour at 0 °

If we use 90mm T33 APBC as reference being able to penetrate 210-211mm at 0 ° (Pre-Deformation penetration) to calculate 2 pounder AP penetration using Jacob Demarre equation, we get 88-89mm at 0 ° for 2 Pounder AP.

UK steel was probably slightly bit lower BHN than US test steel as well.

[Laurelix]

So whilst T33 APBC is a 210-211mm penetrating round that deforms to do 165mm at 0 degrees of penetration…

The 122mm BR-471 AP is a 252-253mm penetrating round that deforms to do 205mm at 0 degrees of penetration

@Reiksknight youll find this interesting.

[Valkay]

This is all really fancy, but what would you like to do with these stats?
Ask for IS-2 buff or ask for a new SU tank?

[Laurelix]

My bug report regards to gaijins incorrect non capped AP penetration calculation has already been Acknowledged.

https://community.gaijin.net/issues/p/warthunder/i/hLPH8HLThguu

Just matter of time. The fix will basically buff the IS-2 penetration to the figures stated above.

[VoyoMayPL]

So cap helps penetration, ok.
How does this explain that soviet AP with less raw pen is better than german APCBC?
I’m confused.

[Laurelix]

It’s all explained in the post. But in short
The AP without the anti deformation cap no longer deforms against highly sloped armour because the unprotected tip no longer strikes the armour first that’s why.

That’s why the 88mm is much better at dealing with its own flat turret front armour than the 122mm but the 122mm is much better at dealing with the highly sloped armour of the T-44 and IS-3

[VoyoMayPL]

Ah, ok. For some reason I forgot to take slope into account.

[Reiksknight]

However, if they were using material fha, such as the Panzer III and Panzer IV, they would be extremely vulnerable to the m4 Sherman’s m61 penetrators, which could penetrate the 80mm frontal hull armor of the later production Panzer IV at 1500 yards

[Reiksknight]

You can refer to this

[Laurelix]

FHA has a brittle surface area with normal RHA behind it so there’s ductility

The non capped AP shell tip deform more against the face Hardenned surface causing them to deform more.

But the anti deformation cap protects the tip and the brittle surface area ends up being more of downgrade in protection as a result.

Furthermore FHA armour takes longer working hours to be produced whilst RHA is easier and more simple

[Reiksknight]

I was worried that the production team would only end up giving the m26 Pershing m82 armor-piercing rounds, and for that I was worried