VULNERABILITY OF GERMAN TANK ARMOR
Tactical and Technical Trends, No. 8, September 24th, 1942
British forces in the Middle East have recently carried out tests with captured German tanks in order to determine the effectiveness of British and U.S. weapons against them.
The 30-mm front armor of the original German Mark III tank (see this publication No. 3, page 12) is apparently a plate of machinable-quality silico manganese. The additional 30- or 32-mm plates which have been bolted onto the basic 30-mm armor are of the face-hardened type. This total thickness of 60 to 62 mm stops the British 2-pounder (40-mm) AP ammunition at all ranges, breaking it up so that it only dents the inner plate. The U.S. 37-mm projectile, however, with its armor-piercing cap, penetrates at 200 yards at 70°. Against the 6-pounder (57-mm) AP and the 75-mm SAP, this reinforced armor breaks up the projectile down to fairly short ranges, but the armor plate itself cracks and splits fairly easily, and the bolts securing it are ready to give way after one or two hits. If 75-mm capped shot is used, however, such as the U.S. M61 round, the armor can be pierced at 1,000 yards at 70°.
Similar results may be expected against the reinforced armor of the Mark IV.
The new Mark III tank has a single thickness of 50-mm armor on the front, and this was found to be of the face-hardened type. The 2-pounder AP projectile penetrates by shattering the hardened face, but the projectile itself breaks up in the process and the fragments make a hole of about 45 mm. The 37-mm projectile does not shatter during penetration, which is secured at ranges up to 500 yards at 70°. The 50-mm plate is softer than the reinforced 32-mm plates being 530 Brinell on the face and 375 on the back. This plate is not particularly brittle and there is very little flaking.
In tests carried out against the side armor of both the old and new models of Mark III tanks, it was found that this armor showed signs of disking at the back. There is also internal petaling. This, and the condition of the front, which is flaked back at 45° for a short distance, indicates that the heat treatment makes the inner and outer skin harder than the core.
The Mark IV has only 22 mm of armor on the sides, but this is reinforced by an additional thickness of 22 mm covering the whole fighting and driving compartments. These additional plates are of the machinable type, and the hardness of this plate was found to be 370 Brinell. The bolts holding this extra armor in place are weak, and it was found that the threads stripped easily.
The above table shows the ranges at which the different types of German tank armor are penetrated by standard U.S. and British weapons. The angles of impact are determined by the normal slope of the armor on the tank