After the Battle of Crete the Luftwaffe ordered a light multi-purpose machinegun. The Fallschirmjäger units on Crete fought with MP40 sub-machine guns, 98K Mauser rifles, MG 34 machineguns, pistols and hand grenades against the well-equipped English and Greek forces which resulted in a high casualty rate on the German side. The small arms were separately dropped in canisters together with the German Paratroopers. Due to their harness and the way the German Paratroopers landed they could not carry heavy equipment on their body during a jump. The Greeks and British defenders had long distance machineguns and used them effectively to inflict heavy casualties on the German paratroopers who had to reach their weapon cannisters. The Fallschirmjägers were at a disadvantage.
Hermann Göring urged to develop of a new weapon for his paratroopers. The experience from the Battle of Crete resulted in the need of a weapon which could be carried by the Fallschirmjägers during a parachute jump. The order was given to develop a selective-fire hand held riffle with the rate of fire of the MP40 sub-machine gun, the range and accuracy of the 98K Mauser rifle, the suppressing capability of the MG 34 machine gun. It would not be longer than 1 meter, no heavier than the K98 Mauser rifle, capable to mount a bayonet, fire rifle grenades and use a detachable 10 to 20 round magazine.
Adolf Hitler changed his mind about the use of Paratrooper units after the Battle of Crete (Operation Mercury) and all plans were terminated. Hermann Göring privately interfered and ordered continuation of the project.
It was quite a list of requirements but Rheinmetall pulled it off and acquired almost all requirements or got very close to them. After tests and further development the Fallschirmjägergewehr 42, FG 42, was a fact. The automatic rifle was equipped with a ZFG42 or ZF4 scope with 4X magnification and a bipod. The gun had integral rails on the receivers to allow mounting of small optical sights, and the iron sights could be folded down for a clear field of view. You might still see some of these features on more modern rifles.
After the first model was tested combat some faults became apparent and small incremental changes were made which resulted in the second model of the FG 42. The third and last model changed the look of the rifle. The last FG 42’s were bulkier and heavier, which aided automatic fire somewhat. They used a wooden buttstock, and had improved bayonet retention. The grip was changed to a much more orthodox vertical design, and the bipod was moved from the midpoint of the barrel out to the muzzle. An adjustable gas regulator was also added to the third model guns.
The difference between model 1 and 2 is minimal, so this is often seen as 1 model.
About 7000 Fallschirmjaegergewehr 42 rifles were made during the war. They used 7,92mm Mauser rifle cartridges with 10 or 20 rounds and had a rate of fire of 750 rounds a minute (third model). It had an effective firing range of 600 meters. Model III weighted 4,95 kg and was 97,5 cm long.