Armor quality of Panzer III and IV

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Peasant
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Re: Armor quality of Panzer III and IV

Post by Peasant » 21 Jul 2020 14:45

Mobius wrote:
20 Jul 2020 23:37
I don't see any connection to fuse speed.
If a shell with bigger delay explodes before it crosses the distance between the screen and the main armour, then the one with a smaller delay would definitely fail as well.

One thing I'm dubious about. 0,016s delay on an AP shell seems like a lot. For 612m/s striking speed it crosses 9,7m before exploding. Maybe its actually 0,0016s?

Edit: Interesting document with much data of fuzes: https://bulletpicker.com/pdf/MIL-HDBK-1 ... f#page=201
critical mass wrote:
21 Jul 2020 10:15
Fuse delay is not enough. The fuse, too needs to stay intact during penetration AND the shell body needs to stay undamaged (no crack through to the cavity).
Hitting a relatively hard target approaching 0.8-1.0 cal/D, or a softer target at elevated velocity will break up the projectile before any fuse action can detonate the HE element.

the shelks were ok for 0.5cal/t ratio and medium velocity, only. The HE is pretty wasted here.
Well good thing the screen on Pz.III was 20mm thick so no problems here.

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Re: Armor quality of Panzer III and IV

Post by Mobius » 21 Jul 2020 17:47

Peasant wrote:
21 Jul 2020 14:45
Mobius wrote:
20 Jul 2020 23:37
I don't see any connection to fuse speed.
If a shell with bigger delay explodes before it crosses the distance between the screen and the main armour, then the one with a smaller delay would definitely fail as well.

One thing I'm dubious about. 0,016s delay on an AP shell seems like a lot. For 612m/s striking speed it crosses 9,7m before exploding. Maybe its actually 0,0016s?

Edit: Interesting document with much data of fuzes: https://bulletpicker.com/pdf/MIL-HDBK-1 ... f#page=201
critical mass wrote:
21 Jul 2020 10:15
Fuse delay is not enough. The fuse, too needs to stay intact during penetration AND the shell body needs to stay undamaged (no crack through to the cavity).
Hitting a relatively hard target approaching 0.8-1.0 cal/D, or a softer target at elevated velocity will break up the projectile before any fuse action can detonate the HE element.

the shelks were ok for 0.5cal/t ratio and medium velocity, only. The HE is pretty wasted here.
Well good thing the screen on Pz.III was 20mm thick so no problems here.
So 20mm might reduce the resultant velocity by about 35m/s.

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Re: Armor quality of Panzer III and IV

Post by L/24Stug » 21 Jul 2020 18:49

If at 600 m/s we take 80mm as the maximum penetration thickness, then remaining velocity for 80mm plate would be 0 m/s.

So deceleration rate would be 600/80 = 7.5m/s each millimeter of armor if it was more o r less a linear function.
Then 20mm would decelerate the projectile 20 * 7.5 = 150 m/s and remaining velocity would be 400 m/s.

Then with a fuse delay of 0.016s, The projectile travels 6.4 meters until it burst.
This would mean that spaced armor possible advantage is not related with fuse detonating before main armor. We must look for another explanation.
Perhaps was related with decapping effect of the 20mm plate? And was the main armor face hardened?

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Re: Armor quality of Panzer III and IV

Post by Peasant » 05 Aug 2020 18:09


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Re: Armor quality of Panzer III and IV

Post by Peasant » 11 Aug 2020 18:37

Points of interests: the face hardened plate badly damaging the 37mm M51 APC projectile in two instances, even at these lower velocities. Second, the size of the hole made by CP is bigger at higher striking velocities.
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Re: Armor quality of Panzer III and IV

Post by Contender » 06 Sep 2020 15:12

So this is test is against 30 mm plates?

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Re: Armor quality of Panzer III and IV

Post by Peasant » 06 Sep 2020 16:27

Contender wrote:
06 Sep 2020 15:12
So this is test is against 30 mm plates?
It reports thickness as "1 1/4in.", closer to 32mm than to 30mm it nominally had.

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Re: Armor quality of Panzer III and IV

Post by Contender » 06 Sep 2020 16:50

Peasant wrote:
06 Sep 2020 16:27
Contender wrote:
06 Sep 2020 15:12
So this is test is against 30 mm plates?
It reports thickness as "1 1/4in.", closer to 32mm than to 30mm it nominally had.
Ty, well its odd that they would test vs 30-32 mm plates when Panzer III's were upgraded with 30 mm + 30 mm starting in 1940 during the France campaign:
Image

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Re: Armor quality of Panzer III and IV

Post by Peasant » 22 Oct 2020 09:37

Alright I've been meaning to do this since the beginning of this week, and finally I got time to do it. I've translated this text with automatic tools first and then proof read it fixing the most egregious issues but let me know if anything is unclear:
It so happened that in the fall of 1939, two damaged German tanks were discovered and secretly removed in Poland, which were carefully examined during the following year at the NIBT testing grounds. The PzKpfw II light tank was almost intact, but did not cause any particular emotions. Was of note the use of 15-20 mm sheets of cemented armor for protection, a successful engine design (the engine was transferred to the Yaroslavl plant for study in order to develop a project for a similar product with a capacity of 200-250 hp), a gearbox and a cooling system, but in general the tank did not overly impress the soviet examiners.

A completely different impression upon closer examination caused the PzKpfw III, referred to in the ABTU documents as the "20-ton Daimler-Benz medium tank". With a mass of about 20 tons, it was protected by 32 mm cemented armor, had a compact 320 hp gasoline engine, with a well designed power and cooling systems, excellent observation devices and, most importantly, a commander's observation cupola on the roof of the turret. Apparently, it was not possible to restore the indicated tank to a running conditions, since in the spring of 1940 the armor plates of its hull were tested by shelling from anti-tank guns and anti-tank rifles. And in 1940 the same model of tank, only fully serviceable, was bought in Germany and delivered to Kubinka for mobility trials.

Image
General view of the PzKpfw III Ausf G. 1940 tank purchased in Germany.

Image
A cut fragment of the 32-mm side armor of the PzKpfw III tank after firing with a series of five 45-mm shells (2 holes). The meeting angle is about 30 degrees. 1940.

Further in our story there will be some ambiguities. The fact is that in domestic documents both of these tanks are referred to as T-III G, but if this is probably true for the purchased vehicle, then the modification of the vehicle captured in Poland was apparently Ausf F, and the letter "F" turned from typewritten capital letter G by hand drawing the small crossbar. In addition, all correspondence on tanks dates from the fall-winter of 1940, and it is not always clear from the context of the letters which one (of the two) vehicles are we talking about? Also, unfortunately, the complete set of reports on the tests of the purchased tank has not yet been found, since they were conducted under the personal supervision of the Deputy People's Commissar of Defense for Armaments. Nevertheless, we must state that the German medium tank amazed our specialists.

First, with the quality of it's armor.

Even in the process of capturing and secretly transporting the indicated tank was fired at from a distance of 400 m with a 45-mm ATG, two shots were fired, which did not penetrate the side armor 32 mm thick. The standard armor-piercing projectile BR-240 left on plate two rounded "craters" with a depth of 18 and 22 mm, but the back of the plate was not damaged, only bulges with a height of 4-6 mm formed on the surface, which were covered with a network of small cracks.

Interestingly, the mention of this prompted the desire to do the same experiment at the NIBT testing grounds in the fall of 1940. But here, shooting from a specified distance at an angle of encounter from normal to 30 degrees, two (out of five shots) pierced the specified armor. Deputy People's Commissar of Defense for Armaments G. Kulik authorized an inquiry through the technical department of the NKV and GAU under the leadership of E. Satel, which showed the following:

“... The shelling of a German medium tank with an armor-piercing shell from a 45-mm cannon places its armor at the limits of capability of this gun, since the mentioned German cemented armor 32-mm thick is equivalent to 42-44-mm of domestric homogeneous armor of the IZ type. Thus, in case of shelling the side of this tank at an angle greater than 30 degrees defeats incoming shells, likely because the surface hardness of German armor is extremely high ...

Image
Drawing PzKpfw III from the brochure "Foreign tanks" 1940 edition.

In this case, the situation was aggravated by the fact that when firing, shells of 1938 production were used with poor-quality heat treatment of the body, made through a simplified production process in order to increase the yield ... which led to increased fragility of the shell and its splitting when overcoming thick armor of high hardness.

Details about the shells of this batch and the decision on their withdrawal from the troops were reported to you on 06/21/1939 ...

The investigation convincingly shows that, despite the specified decision to withdraw, a large number of 45-mm armor-piercing shells in that military unit, as well as in the neighboring one, have the same brands and, apparently, the same defect ... Thus, the withdrawal of these shells from the troops, is not yet complete and currently the shells produced in 1938 are still present side by side with new ones of normal quality ...

When firing at the tank's armored hull at the BT-proving grounds, 45-mm BRZ-240 shells from 1940 production were used, which are free from the indicated defect and fully satisfy the technical requirements ... "
Source: https://readli.net/tankovaya-moshh-sssr ... kuyu-poru/

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Re: Armor quality of Panzer III and IV

Post by Peasant » 27 Oct 2020 12:29

Source: https://tanksalotweb.com/2017/08/03/vul ... or-pz-iii/

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Image

Interestingly this source seems to imply that only the additional 30mm add-on plates were face hardened, while the basic armour was not. Economically speaking this makes sense.

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Re: Armor quality of Panzer III and IV

Post by critical mass » 27 Oct 2020 20:35

Also protectionwise. The principal function of the face hardened plate is to induce change of shape effects on the projectile, ideally causing full shatter. Fragments of the shell can be more reliably arrested by a 2nd, MQ (RHA) grade armor plate. Another FH armor plate would make sense against APCR/APNCR/HVAP type of projectiles but not against full calibre solid AP or it´s fragments.

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Re: Armor quality of Panzer III and IV

Post by Contender » 27 Oct 2020 21:17

Peasant wrote:
27 Oct 2020 12:29
Interestingly this source seems to imply that only the additional 30mm add-on plates were face hardened, while the basic armour was not. Economically speaking this makes sense.
30 mm Panzer armor was FHA as standard in which case face hardening the 30 mm frontal plates would need to have been dropped during production, I don't know if there is any record from armor production sources that show the abandonment of FHA for 30 mm frontal plates so either this is a mistake of the document or they did indeed drop face hardening during production once the upgrade became accepted as standard. In either case this should still leave a large amount of vehicles that were upgraded in the field with FHA + FHA frontal plates.
Last edited by Contender on 27 Oct 2020 22:05, edited 5 times in total.

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Re: Armor quality of Panzer III and IV

Post by Richard Anderson » 27 Oct 2020 21:26

Peasant wrote:
27 Oct 2020 12:29
Source: https://tanksalotweb.com/2017/08/03/vul ... or-pz-iii/

Image

Image

Interestingly this source seems to imply that only the additional 30mm add-on plates were face hardened, while the basic armour was not. Economically speaking this makes sense.
Interesting. I wonder what "75mm SAP" is? The APC is as they say 75mm APC M61. Are they referring to M72? If so, it should be referred to as AP Shot or the like, not "SAP"?
"Is all this pretentious pseudo intellectual citing of sources REALLY necessary? It gets in the way of a good, spirited debate, destroys the cadence." POD, 6 October 2018

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Re: Armor quality of Panzer III and IV

Post by Yoozername » 28 Oct 2020 00:14

Perhaps Solid Armor Piercing? Which would be M72

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Re: Armor quality of Panzer III and IV

Post by Peasant » 28 Oct 2020 16:32

Contender wrote:
27 Oct 2020 21:17
30 mm Panzer armor was FHA as standard in which case face hardening the 30 mm frontal plates would need to have been dropped during production, I don't know if there is any record from armor production sources that show the abandonment of FHA for 30 mm frontal plates so either this is a mistake of the document or they did indeed drop face hardening during production once the upgrade became accepted as standard. In either case this should still leave a large amount of vehicles that were upgraded in the field with FHA + FHA frontal plates.
Good point. But I'm wondering whether the field workshops of Pz.Div. had the equipment necessary to drill the holes in the plates that were already assembled into a vehicle, as opposed to those made during production which, I assume, were drilled before being welded into a tank, because it sounds much easier to do.
Because if the vehicles delivered to the troops with the bolts already installed had RHA plates mounted as the basic layer, then Pz.IIIs with FHA+FHA arrangement may have not existed at all.

A bit of info from Panzertracts 3-2:
Image

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