Column of Panzer III Ausf J
Efforts were made to rapidly initiate production of the 5cm KwK39 L/60 gun, resulting in the Ausf J series being divided between it and the 5cm KwK L/42. In August 1940, Hitler had originally ordered the L/60 gun, but the Waffenamt did not act on it, citing the recent success of the L/42. However, after seeing the Pz Kpfw III Ausf J without the long gun at his birthday demonstration in April 1941, Hitler insisted on its installation as soon as possible. The need for more powerful armament became apparent during events in Russia two months later. The only differences between the Ausf J with the 5cm KwK L/42 and those with the 5cm KwK39 L/60 were the gun itself and the ammunition storage, which had to be reduced due to the increase in shell length. The long 5cm KwK proved to be very effective in North Africa against tanks like the Grant and Valentine, but had little impact in frontal engagements with Russian T-34 or KV-1 tanks.