DTD Testing of Panzer III Armour Plate

[ClintHardware]

I have been looking again at 2-Pdr performance and came upon several tests in the UK performed on sections cut from the front hull of more than one Panzer III. The various examples of plates were probably cut from the panzers and flown back to save time and possibly relate to panzers lost to the Germans during Crusader, but not necessarily. In the following test summary the total test piece was three plates welded to each other and appear to be under any externally added extra armour. The tests I have been looking at involved firing 2-Pdr AP, APC, APBC and APCBC even though two of these types were not issued IIRC.

The following is not conclusive but is of interest only.

D.T.D. EXPERIMENTAL REPORT AT 37. (Based on testing during May 1942)
Interim Report on Ballistic Properties of Armour from Front of Pz. Kw. III. (A.E.C.)

SUMMARY

A piece of the most prominent hull front plate from the vehicle has been proved with the 2-pdr. The plate was mounted in the vehicle with a forward tilt of 20 degrees. It was 31.2 mm. thick and the hardness of the face was over 500 Brinell. When struck with one round of 2-pdr. A.P. at 20 degrees and 1497 f.s. (Horizontal fire parallel to the line of approach of the tank at a range of approximately 1200 yards with M.V. 2600 f.s), the plate split in two. One of the pieces broke up after two more rounds of 2-pdr A.P.C. at 20 degrees and approximately 1500 f.s. The other piece broke up after one more round of A.P.C. at 30 degrees and 1634 f.s. (Horizontal fire at 23 degrees to the line of approach at a range of approximately 1000 yards.)

The behaviour of two main welds and of the welds by which certain fittings were attached to the inside of the plate was also examined. The main welds were only moderately satisfactory. Of four fittings, one flew off at the first impact, one flew off when the plate directly opposite it was struck, and two remained in position despite a near impact. In the first case the welding was very poor; in the second, it was of moderate quality.

Although the armour when under trail was not supported as it would be in a tank, we are of the opinion that it is so brittle that even in situ it would not stand up successfully to 2-pdr. attack at short ranges or to 6-pdr. attack at moderate ranges.
WO 194/1415

[ClintHardware]

I will add that the plates were welded together end on and were the original armour plates of the panzer to which any external additional plates would have been added.

[Urmel]

Define 'short' and 'moderate', Mr. Tester.

Maybe they should have put the bloke on a plane to North Africa to demonstrate this in situ during a German tank attack?

[Don Juan]

As Urmel said, unless what "short" range means is defined, these results are pretty meaningless. Tests in the UK and the Middle East on extant hulls gave the 2 pdr AP at 2600 fps a penetration of the frontal armour of the up-armoured Panzer III's of between 0 and 200 yards at 30 deg.

Interestingly, though, the Soviets conducted tests which indicated that some Panzer III's had armour of very poor quality:

http://tankarchives.blogspot.co.uk/2014 ... rmour.html

The tendency for the Germans to produce the occasional shocker persisted:

http://tankarchives.blogspot.co.uk/2017 ... ality.html

It's worth noting that not a single Panzer III or Panzer IV that the British captured (and they captured loads of them) was in sufficiently good mechanical condition to undergo running trials, which is why so many of them were shot up. That tells you all you need to know about the durability of these machines.

[ClintHardware]

Well everyone knows what moderate and short means why are you even asking me?

But seriously I agree they are virtually meaningless. The next chunk I have will be (IIRC) more useful but not extremely useful but at least interesting.

[Urmel]

It's worth noting that not a single Panzer III or Panzer IV that the British captured (and they captured loads of them) was in sufficiently good mechanical condition to undergo running trials, which is why so many of them were shot up. That tells you all you need to know about the durability of these machines.

Not sure that is the right conclusion to draw. Any vehicles captured would have been shot up, or broken down, with issues presumably ranging from complex to simple failures (e.g. a broken track). The policy appears to have been to then terminally disable the vehicles, rather than preserve them in a state that would enable repair. For example, the South African engineers blew up 35 German tanks captured in the D.A.K. workshops in mid-December 1941.

[Don Juan]

There were a few tanks that they captured that were earmarked for test, but it was quickly found that they were mechanically worn out. IIRC, in William Blagden's Middle East AFV Technical Report No.2, they forwarded a Panzer III to the MEE at Abbassia for trials, but as soon as they tried to run it, they realised it was a non-runner.

One Panzer IV was shipped to the UK for trials, but it was the same story. The tank was sent to Leyland Motors for rebuilding, who issued a report on it. I haven't been able to track down this report, but as far as I can tell Leylands only got a short mileage out of it. The tank was supposed to be returned to the FVPE for trials, but these never happened.

On the other hand, a Panzer II that was captured was run up to a mileage of over 7000 miles at the FVPE, proving that this was a particularly durable and reliable tank.

[Urmel]

Yes, but it’s still luck of the draw. They captured a brand-new Panzer III near Benghazi in December, odometer at 20km or something ridiculous like that. (I’ll check when I get to it). I presume with all the chaos it never made it to Egypt.

[Don Juan]

That tank must have been landed at Benghazi then?

This is something I've been thinking about for a while - why didn't the Germans land more tanks at Benghazi, and therefore cut out the wear induced by driving from Tripoli. I assume it was simply because it was a more hazardous port to reach, or was more in the range of British bombers.

Also, after Crusader, Rommel's winter offensive had the advantage of re-taking Benghazi - was the capture of the port one of the reasons why this offensive was undertaken?

There was such an advantage in landing tanks at Benghazi I can't understand why comparatively few were landed there.

[ClintHardware]

I have no specific evidence to hand to make the following observations, so this is from general observations over time:
1) The Benghazi route shipping was under daily air attack, when found, so risking panzers taken there by sea was probably too risky under common daily circumstances.
2) The number of times panzers were struck by 2-Pdr and 25-Pdr ammunition and then repaired for whatever reason would leave you by the time of Crusader with a lot of dented, scarred and worn looking panzers.
Urmel has done a brilliant job on shipping data and I am not arguing with his figures. I am still left with the impression that more panzers than we know arrived in North Africa but I have no hard specific evidence of that - so it remains an unanswered question and NOT in anyway a fact.

For those who do not want the question even raised: it has been and will be raised and it is not an opinion, it is a question.

[Urmel]

Yes, south of Benghazi I think. I need to find the relevant information again. Came in on Ankara (which had her own heavy lifting cranes) on 22 or 23 December 41.

As for why Benghazi wasn’t used more, it’s complicated.

Benghazi couldn’t really take larger vessels than 2,500 tons (ish) in 1941, not sure that was ever fixed. It also couldn’t take more than two vessels at a time. I’m also not sure if it had the 20 tin cranes needed to unload tanks there.

Benghazi was considerably less safe, subject to air and submarine interdiction and mining.

Italian escort assets were scarce on the ground, so they focussed on one route where the best overall outcome could be achieved.

[critical mass]

There are certain caveates with thesse DTD trials.

A) The plates tested were face hardened
Rigid FH plates cannot fail by ductile hole formation. They will always fail by plugging / discing, which may be viewed as one of the more brittle types of failure mode. FH plate relies not on it´s own strength but on the ability to shatter the projectile, which the Pz-III plate did just fine, even at the low velocities tested here (1497-1600´s fps). This tends to indicate a good ability of the FH Pz-III plate to damage AP and even capped AP projectiles.

B) the plates were removed from a PzIII hull with help of a cutting torch.
This is a significant information because use of a cutting torch means that the plate is subject to a secondary heat treatment, which includes heating within the heat affected zone and subsequent air-cool.
Surface hardened plates do not behave nicely under reheat-treatment and the aircool is almost set to embrittle the plate by definition. That´s why the use of cutting torches were prohibited for intact armor plate, or the plate had to be discarded.

C) actual resistence of the plate does not compare unfavourably with official british 2pdr AP and APCBC penetration data vs contemporary british FH armor.

[Dili]

Yes, south of Benghazi I think. I need to find the relevant information again. Came in on Ankara (which had her own heavy lifting cranes) on 22 or 23 December 41.

As for why Benghazi wasn’t used more, it’s complicated.

Benghazi couldn’t really take larger vessels than 2,500 tons (ish) in 1941, not sure that was ever fixed. It also couldn’t take more than two vessels at a time. I’m also not sure if it had the 20 tin cranes needed to unload tanks there.

Benghazi was considerably less safe, subject to air and submarine interdiction and mining.

Italian escort assets were scarce on the ground, so they focussed on one route where the best overall outcome could be achieved.

Why? destruction made by occupation in earlier 1941?

[critical mass]

"The other piece broke up after one more round of A.P.C. at 30 degrees and 1634 f.s. (Horizontal fire at 23 degrees to the line of approach at a range of approximately 1000 yards.)"

That FH plate tested was only 31.2mm at 30° vs capped A.P. However, when compared to period british penetration tables for 2pdr at 30° with an 80% probability of success for capped (...and ballistic capped*...) A.P. at 1000yd, one would recognize that the 2pdr capped A.P was rated to perforate much thicker FH plate: not 31.2mm but 49.3mm(!), that´s a whopping 58% thicker plate! In order to be inline with british FH material, they´d had to test not at 1634fps but at around ~1000 fps in order to simulate ranges of ~2600 yd in order to get a realistic result (compare that at 2000 yd, capped A.P. was still expected to defeat 36.1mm britihs FH at 30° and at 80% of the time!). Not sure what they intended to test for with this trial but either they rated the Pz III armor plate resistence considerably higher than their own FH plate (likely, because the A.P. trials too, where conducted under biased condition) or else (also probable), they tested for shatter effects of the capped A.P. The presence of a cap was intended to negate shatter altogether but apparently, the face hardened plate succeeded in inducing shatter on impact at rather low velocity vs this 0.78cal/d plate despite the presence of a capped A.P. Depending on from which angle You look at it, one might view this either as an exceptionally good result from the armor plate´s point of view (face hardened plates work by damaging the attacking projectile) or, alternatively, as an extremely disappointing result from the projectile´s point of view (capped A.P. suffered shatter like uncapped A.P. did).

The 20° capped A.P. tests are also instructive. They once did crack the plate due to EDGE EFFECTS (projectile condition unknown) and once shattered and obtained only partial penetration (base in front of plate, rest presumed to been through) at 1496/1502fps. This velocity equals to 1200yd range with 2pdr (i.V.=2600fps). At this range however, capped A.P. was rated with 80% penetration est. in order of 46mm british FH at 30°! Notice that the actual Pz III plate test at only 20° is considerably easier for the projectile than a 30° impact would have been, and that the Pz III´s 31.2mm plate are objectively thinner than the british 46mm estimate, so we can be readily sure due to the PP event that this plate, beyond doubt, acted ballistically of considerably superior resistence when directly compared to british FH plate and that the difference is large enough to not merely just constitute a quibble.

at 20° they tested the Pz III plate at De Marre K=2200
at 30° they tested the Pz III plate at De Marre K=2400
british FH plate at this velocity and 30° was penetrated (80%) at De Marre K=1740 to K=1800.

These discrepiancies are in my opinion only plausibly explainable by the lack of shatter when british capped A.P. strikes british FH plate and full shatter (despite presence of a cap!) when striking Pz III armor.

*) the lightweight, ballistic cap is not a substantial contributor to penetration

[Don Juan]

"The other piece broke up after one more round of A.P.C. at 30 degrees and 1634 f.s. (Horizontal fire at 23 degrees to the line of approach at a range of approximately 1000 yards.)"

That FH plate tested was only 31.2mm at 30° vs capped A.P. However, when compared to period british penetration tables for 2pdr at 30° with an 80% probability of success for capped (...and ballistic capped*...) A.P. at 1000yd, one would recognize that the 2pdr capped A.P was rated to perforate much thicker FH plate: not 31.2mm but 49.3mm(!), that´s a whopping 58% thicker plate! In order to be inline with british FH material, they´d had to test not at 1634fps but at around ~1000 fps in order to simulate ranges of ~2600 yd in order to get a realistic result (compare that at 2000 yd, capped A.P. was still expected to defeat 36.1mm britihs FH at 30° and at 80% of the time!). Not sure what they intended to test for with this trial but either they rated the Pz III armor plate resistence considerably higher than their own FH plate (likely, because the A.P. trials too, where conducted under biased condition) or else (also probable), they tested for shatter effects of the capped A.P. The presence of a cap was intended to negate shatter altogether but apparently, the face hardened plate succeeded in inducing shatter on impact at rather low velocity vs this 0.78cal/d plate despite the presence of a capped A.P. Depending on from which angle You look at it, one might view this either as an exceptionally good result from the armor plate´s point of view (face hardened plates work by damaging the attacking projectile) or, alternatively, as an extremely disappointing result from the projectile´s point of view (capped A.P. suffered shatter like uncapped A.P. did).

The 20° capped A.P. tests are also instructive. They once did crack the plate due to EDGE EFFECTS (projectile condition unknown) and once shattered and obtained only partial penetration (base in front of plate, rest presumed to been through) at 1496/1502fps. This velocity equals to 1200yd range with 2pdr (i.V.=2600fps). At this range however, capped A.P. was rated with 80% penetration est. in order of 46mm british FH at 30°! Notice that the actual Pz III plate test at only 20° is considerably easier for the projectile than a 30° impact would have been, and that the Pz III´s 31.2mm plate are objectively thinner than the british 46mm estimate, so we can be readily sure due to the PP event that this plate, beyond doubt, acted ballistically of considerably superior resistence when directly compared to british FH plate and that the difference is large enough to not merely just constitute a quibble.

at 20° they tested the Pz III plate at De Marre K=2200
at 30° they tested the Pz III plate at De Marre K=2400
british FH plate at this velocity and 30° was penetrated (80%) at De Marre K=1740 to K=1800.

These discrepiancies are in my opinion only plausibly explainable by the lack of shatter when british capped A.P. strikes british FH plate and full shatter (despite presence of a cap!) when striking Pz III armor.

*) the lightweight, ballistic cap is not a substantial contributor to penetration

Since every person who contributes to this forum has known for years that 2 pounder AP was useless against German face hardened armour at a distance over 100 yards, and that 2 pounder APCBC arrived too late for use in the Middle East and North Africa, what on earth are you trying to prove with this?