"4. Quality of armour based on damage
Light anti-bullet armour, 8-15 mm thick
German and Czechoslovak homogeneous armour with Brinell hardness of 2.6-2.85, when hit with a 12.7 mm DShK bullet at a speed of 840 m/s holds approximately as well as domestic armour.
However, the presence of spalling of the German armour, in up to 85% of penetrations, indicates that the armour is very brittle, due to its high hardness. The brittleness is demonstrated when a DShK fires in bursts, armour fragments of up to 40-50 mm in size fall off, but without cracks.
45 mm shells give the same result. Breaches in armour, usually 1.5 times the caliber size, are formed. The edge of the breach is always very dry, crystalline. In some cases, the metal shows separating layers.
However, despite the brittleness of the armour, no through cracks were developed, likely due to the plate's thinness and low pressure on it.
Anti-shell armour, 20-40 mm thick
20-40 mm thick armour is homogeneous, hardened to 3.0-3.2 on the Brinell scale.
The resistance of the captured samples largely coincides with technological norms in the production of domestic armour.
However, despite the decreased hardness of anti-shell armour of PzIII tanks compared to anti-bullet armour, the amount of brittle damage is significantly higher. The behaviour of vehicle #233 is characteristic of the tanks: 75% of all penetrations resulted in fragments up to 3 calibers in size spalling off, as well as through cracks, resulting in the armour plate falling into pieces. Identical behaviour was observed with the surface-hardened armour on vehicle #131.
The armour of captured tanks is of low quality, and based on existing technical conditions for domestic armour, would be deemed unacceptable, due to its brittleness, cracking, and spalling.
Conclusions: based on the above, the following conclusions can be made:
- The armoured steel of captured tanks is usually more hardened than domestic steel. The chemical composition of captured steel provides nothing interesting for domestic metallurgy.
- Typically, only homogeneous high hardness armour is used. Heterogeneous (cemented) armour is used only for reinforcing front armour plates (armour screens).
- Despite the high hardness, the quality of the foreign armour is lower than domestic homogeneous armour.
- The layering characteristics of foreign armour are generally good by the standards of domestic armour.
- Based on the technical standards of domestic armour, captured German armour is unacceptable, due to its brittleness and tendency to crack, spall, or fragment when hit."