Tuesday, 4 February 2014

PzIII Armour

As a part of the agreement between the USSR and Germany, the USSR received a sample of Germany's latest and greatest in tank development. That latest and greatest was the Panzerkampfwagen III. After mobility trials, the tank was literally torn to pieces. Many things about it were interesting to Soviet engineers: the torsion bars, commander's cupola, gun position indicator, instrument panel, machinegun layouts, and its armour. These components were shipped to relevant factories and organizations for further study. The armoured hull went to the Izhor factory, where scientists from NII-48 began their experiments. Here is how the armour fared during trials.

"3. Proving grounds trials.

Trials were, at first, done with a 45 mm blunt-nosed shell from the anti-tank gun, then with DK bullets.

Only one shot was fired from the gun, with impact velocity of 533.8 m/sec, which is equivalent to the minimum requirement from GABTU for 30 mm armour. After the shell hit, the plate cracked into 8 parts. Photographs of these parts are shown in figures 4, 5, and 6. Figures 4 and 5 show the place where the shell hit and the nature of the damage to the plate from the front and rear. Figure 6 shows the fracture type on the fragments. The crack is shiny, crystalline, with burrs.

One of the fragments was then trialled with a DK bullet, fired at a speed of 823.2 m/s, from a distance of 100 and 50 meters. The results of the trials are as follows.

  • 100 meters. Hits: 2. Damage: 1 #11 and 1 #13.
  • 50 meters. Hits: 4. Damage: 1 #11, 1 #15, 1 #13 from hitting the location where the armour was prepared for a Brinell test, and one #13 from hitting the welding seam.
Proving grounds trials demonstrated that the metal was very brittle, and had decreased resistance to a DK bullet (PTP at 150 meters with the impact velocity of 840 m/s)."

Fig. 4. Front of the German plate. 

Fig. 5. Rear of the plate. Chalk markings indicate spalling damage from the 6 bullets that hit the plate.

"In order to confirm that the brittleness of the part is not due to its small size, or due to the shell hitting near its edge, the Izhor factory produced an equivalent armour part with hardness of 460-444 on the Brinell scale (probe depth 2.85-2.9 mm) out of batch #78261 of steel grade FD 5654, currently used by the Red Army. The chemical analysis of the part was as follows:
  • C = 0.27
  • Cr = 1.54
  • Ni = 2.32
  • Mo = 0.34
Trials of this part were performed in the same way, at impact velocities of 525.4 m/s and 564.2 m/s. Under these conditions, the rear of the plate does not show damage, and cracks did not form.

The condition of the plate after trials from the front and rear is shown in figures 7 and 8."

Fig. 7. Front of the plate produced at the Izhor factory.

Fig. 8. Rear of the plate produced at the Izhor factory. There is no damage to the rear as a result of the two hits.

"The trials show that the brittleness of the German armour is due to its unsatisfactory characteristics."
CAMD RF 38-11355-208

This is a very rare event, armour from two different countries in the same test, not only of identical thickness, but identical size and shape!

Those insisting that the Germans sent a bad tank on purpose should read the 1942 PzIII tests where the armour also cracks (although not as catastrophically) and the front armour screen falls off.

For an idea of what ranges this would come into play at, a model 1932 45 mm AT gun's BR-240 shell flies at 546 m/s at 1500 meters and at 529 m/s at 1600 meters. Therefore, a the armour sample was hit from an equivalent of  nearly 1600 meters, almost twice as much as the maximum distance attempted in the test. According to Soviet mathematical calculations, the PzIII should be vulnerable from the side until 1100 meters, but in reality was vulnerable from a distance in excess of 1600 meters. Looks like German armour fell short of Soviet standards.


  1. This is extremely interesting. Out of curiosity, who were the people in the testing department, and which bureau usually set all the armor standards? I have been reading about the Oboronka and the Yerzhovschina and the hell designers in the Stalin era could go through, but it seems like they were able to do a remarkably good job in spite of all that.

    1. Standards were set by GABTU, testing was done by lots of people. The major ones were NII-48 (armour) and the NIBT proving grounds at Kubinka.

  2. Interesting. Is there any comparison of GABTU standards with say, British, German, and American armor standards from the same time period? Also, with regards to the use of torsion bars - did the Panzer III's use of torsion bars have anything to do with the KV's use of torsion bars, or is that an unrelated development? Last question - did the Russians send any armored vehicles over in exchange for the Panzer III they received from the Germans?

    1. Sadly, I don't have those comparisons. Also the development of the KV started in 1938, way before anyone in the Soviet Union saw a PzIII.
      I am not aware of any armoured vehicles sent over by the USSR in exchange.

  3. "546 m/s at 1500 meters"? Do you have a firing table for the 45mm?

  4. How about direct link to source?

    We (Pasholok, Shein, Ulanov) are not against translation of documents, but direct link to source welcomed.

    1. Of course, I will include the link to the source from now on.

  5. I wish the Bolshevik Propaganda Ministry would have gotten their stories straight. According to Russian tests the 45mm/L46 either penetrates 35mm or 30mm armor 80% of the time at 1500m So what kind of poor armor was being used in these gun penetration tests if the 45mm can only dent the 30mm ‘currently used by Red Army’ armor at 1500m?

    1. The Russians were testing that 45mm/L46 on a Panzer III with 30mm German armor plates, not Russian plates! The poor armor in question was the real German plates that the Russian gun was expected to face.