The gun was the armament of the Panther medium tank and two variants of the Jagdpanzer IV self-propelled anti-tank gun.

The increased muzzle velocity and operating pressure of the new gun required a new armour-piercing projectile to be designed.

39/42 was the result, and apart from the addition of wider driving bands it was otherwise identical to the older 7.5 cm PzGr.

The breech operated semi-automatically so that after the gun had fired, the empty shell casing was automatically ejected, and the falling wedge type breech block remained down so that the next round could be loaded.

Once the round was loaded the breech closed automatically and the weapon was ready to be fired again.