This flexible 20 mm aircraft machine gun, Oerlikon M.G. F.F., is the German Air Force version of the Swiss Oerlikon 20 mm machine gun.
The weapon is a blowback, inertia-operated, air-cooled machine gun for fixed or flexible mounts. It fires from an open bolt and has an electrically operated trigger mechanism. The cartridge-counting mechanism is also electrically operated. It has a pneumatic charging mechanism to retract the bolt for the first shot.
Some minor modifications of the Swiss version of this machine gun have been introduced. It is chambered to fit the short German 20 mm round, and the travel of the recoiling parts has been redesigned to conform. The barrel has been shortened and the gun lightened considerably. It has been in use in this form without material alteration since the beginning of the war.
The gun was originally intended as a fixed weapon and was termed the M.G. F.F. A later type, the F.F.M., is mechanically the same but in some cases is provided with a cooling cowling and a hand firing device for use as a free gun. It is used both as a flexible and a fixed gun.
SPECIFICATIONS
| Caliber | 20 mm | |
| Weight | 76 1/2 lb. | |
| Length | 57 ins. | |
| Feed | Drum—60 rd. capacity | |
| Length of barrel | 32 1/4 ins. | |
| Cooling | Air | |
| Operation | Blowback (inertia) with solenoid trigger | |
| Fire | Automatic only | |
| Rate of fire | 450 to 500 rds./min.—cyclic |
German: p. 251