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 the 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. A version called the 7. 5 cm FK 7M59 was proposed towards the end of the war to fill a dual-purpose role of field gun and anti-tank gun. The carriage was modified to provide +35° of elevation which increased maximum range to 13,300 m (14,500 yd). Another dual purpose variant was the 7. 5 cm FK 7M85 which used the gun and recoil system of the Pak 40 on the carriage of the 10 cm le FH 18/40.