7.5 cm Pak 40
The 7.5 cm Pak 40 (7,5 cm Panzerabwehrkanone 40) was a German 75 millimetre anti-tank gun developed in 1939-1941 by Rheinmetall and used during the Second World War. The Pak 40 formed the backbone of German anti-tank guns for the latter part of World War II, mostly in towed form, but also on a number of tank destroyers such as the Marder series. Approximately 23,500 Pak 40's were produced.
A modified version of the gun designed specifically for vehicle-mounting was the 7.5 cm KwK 40, which differed primarily in using more compact ammunition which allowed greater numbers of rounds to be carried inside the vehicles. The KwK 40 armed many of the German mid-war tank and destroyer designs, replacing the Pak 40 in the later role.
Depending on the source, the Pak 40 may be referred to as the 7.5/L46, referring to the barrel's length in calibres. There were two versions of the KwK 40, which would be referred to as the 7.5/L43 or 7.5/L48.
Development
Development of the Pak 40 began after reports of new Soviet tank designs began to reach Berlin in 1939. The 5 cm Pak 38 was still in testing at this point, but it appeared it would not be powerful enough to deal with these newer designs. Contracts were placed with Krupp and Rheinmetall to develop what was essentially a 7.5 cm version of the Pak 38. However, while the Pak 38 made extensive use of light alloys to reduce overall gun weight, these were now earmarked for Luftwaffe. As a result, the Pak 40 used steel throughout its construction and was proportionally heavier than the 5 cm model. To simplify production, the Pak 38's curved gun shield was replaced by one using three flat plates.