Several other changes were made to the FG 42 before it was allowed to be made. The first Rheinmetall design used chrome-nickel steel a lot. It was used on many parts which were needed to make the weapon work. There was not much of this material around. When the "Luftwaffe" was allowed to make 3,000 rifles for some more testing, the weapon was changed and manganese steel was used instead of chrome-nickel steel. The Heinrich Krieghoff company was asked to make some FG 42s. This was because Rheinmetall was not large enough to make lots of FG 42s. The weapon was first used by commandos during "Operation Eiche" in 1943. "Operation Eiche" was the dangerous mission that some "Fallschirmjäger" went on. During this mission, they had to rescue Benito Mussolini. The "Fallschirmjäger" team was led by Otto Skorzeny.