The increased muzzle velocity and operating pressure of the new gun required a new armour piercing projectile to be designed. The PzGr. 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. 39. The wider driving bands added a little extra weight, from 6.8 kg for the old PzGr.39, to 7.2 kg for the new PzGr.39/42.
The gun was fired electrically, the primer was initiated using an electric current rather than a firing pin. 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. Three different types of ammunition were used: APCBC-HE, APCR and HE.
Gander, Terry and Chamberlain, Peter. Weapons of the Third Reich: An Encyclopedic Survey of All Small Arms, Artillery and Special Weapons of the German Land Forces 1939-1945. New York: Doubleday, 1979 ISBN 0-385-15090-3
Hogg, Ian V. German Artillery of World War Two. 2nd corrected edition. Mechanicsville, PA: Stackpole Books, 1997 ISBN 1-85367-480-X
Penetration data extracted from a French DoD publication "Le Panther" Ministere de la Guerre, Section Technique de l'Armee, Groupement Auto-Chars, 1947.