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