The 5.2cm shot in a battle report of Lt. Zabel, s.Pz.Abt.503

Here is a famous story of Tiger 231 of s.Pz.Abt.503 referred from Tigerfibel, and you can find also a most similar battle report by Lieutenant. Zabel.
But what is the shots of 5.2cm? I could not find any information in the field-gun or anti-tank gun at those days.
I appreciate your any advice.





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