Type 99 Aircraft Cannon
Dai-Nihon Heiki · Machine Gun · Discontinued · 1939
Also known as: Type 99 Mark 1 Cannon, Type 99-1, Type 99 Model 1, Oerlikon FF derivative
Overview
The Type 99 Mark 1 was a 20mm aircraft autocannon adopted by the Imperial Japanese Navy and best known as the wing-mounted cannon of the early Mitsubishi A6M Zero fighter. Developed under license from the Swiss Oerlikon FF, it used an advanced-primer-ignition (API) blowback action and fed from a 60-round drum magazine. Its low muzzle velocity and slow cyclic rate gave a lobbing trajectory that Allied pilots found hard to aim, but its light weight suited the featherweight Zero airframe. A longer-barrelled, higher-velocity Mark 2 (chambered 20x101mmRB) followed.
Specifications
| Weight (empty) | 23000 g (811.3 oz) |
| Overall Length | 1330 mm (52.36") |
| Barrel Length | 810 mm (31.89") |
| Action Type | Blowback |
| Magazine Capacity | 60 rounds |
| Magazine Type | Drum |
| Muzzle Velocity | 600 m/s (1969 fps) |
| Muzzle Energy | 23040 J (16993 ft·lbf) |
| Effective Range | 600 m (656 yd) |
| Rate of Fire | 520 rpm |
| Barrel Rifling | Right Hand |
| Frame Material | Steel |
| Barrel Material | Steel |
Calibers
- 20x72mmRB · primary — also known as 20mm Type 99 Mark 1, 20x72RB, Oerlikon FF 20mm
Features
- Firing modes: Full Automatic
- Feed systems: Drum Magazine
- Features: Air Cooled, Api Blowback Action, Wing Mounted, Drum Fed, Lightweight Aircraft Cannon
Variants
- Type 99 Mark 2 — Long Barrel
Service history
Operators
- Imperial Japanese Navy · adopted 1940 · as Type 99 Mark 1
Conflicts
- World War II (1941-1945)
Production
Production years: 1939-1945
Total production figures not published; manufactured by Dai-Nihon Heiki throughout the war
Origin
Country of origin: Japan
Discontinued: 1945
Notes
Two principal marks: Mark 1 (short barrel, 20x72RB, ~600 m/s, drum-fed, modelled here) and Mark 2 (long barrel, 20x101RB, ~750 m/s, later belt-fed). Drum capacities of 15/30/45/60 and later 100 rounds were offered. Muzzle energy estimated from projectile weight and velocity.
Background
Its Oerlikon FF lineage made the Type 99 one of the lightest 20mm aircraft cannons of WWII, a perfect match for the featherweight Zero; the same Oerlikon FF design also fathered the German MG FF, making the Zero's cannon and the Luftwaffe's cannon mechanical cousins.