Panzer III
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.