5 cm KwK 38
The 5 cm KwK 38 L/42 "(5 cm Kampfwagenkanone 38 L/42)" was a German 50 mm calibre cannon used as the main armament of variants of the German Sd.Kfz. 141 Panzerkampfwagen III medium tank during the Second World War. There was no towed anti-tank gun equivalent. History. The Panzer III was intended to fight other tanks; in the initial design stage a gun was specified. However, the infantry at the time were being equipped with the PaK 36, and it was thought that, in the interest of standardization, the tanks should carry the same  armament. As a compromise, the turret ring was made large enough to accommodate a gun should a future upgrade be required. This single decision later assured the Panzer III a prolonged life in the German Army. The early Panzer III Ausf. A to early Ausf. G were equipped with a 3.7 cm KwK 36 L/45, which proved adequate during the campaigns of 1939 and 1940. In response to increasingly better armed and armored opponents, the later Panzer III Ausf. F to Ausf. J were upgraded with the 5 cm KwK 38 L/42. And the later Panzer III Ausf. J¹ to  M went with the longer 5 cm KwK 39 L/60 gun. Ammunition. Average penetration performance established against rolled homogenous steel armour plate laid back at 30° from the vertical.