Armament

The Naval 1937 specifications for the 12-Shi fighter called for an armament of two 20mm cannon, two 7.7mm machine guns and provision for two 60kg bombs. Soon after production of the A6M3 Model 32 commenced, ammunition supply for the cannon was increased from 60 to 100 rounds per gun, and this armament was carried forward to the Model 22. The designation Model 22KO (A6M3 Model 22a) was used to denote replacement of the standard cannon with the long-barrel type. In a search for even greater hitting power, a few Model 22s were experimentally fitted with 30mm cannon and operationally tested at Rabaul.
The 7.7mm machine guns, with a magazine of 680 rounds per gun, were mounted to fire over the engine cowl and through the propeller arc. These weapons were similar to the Army's Type 89 gun, a derivative of the Vickers light machine gun. It used disintegrating belt ammunition, could fire at 1000rpm, had an effective range of 600m, a muzzle velocity of 2460ft/sec and had a weight of 26lb per gun.
The wing armament comprised various versions of the Type 99 cannon, a version of the Oerlikon 20mm weapon, manufactured under licence by the Dai-Nihon Heiki Company. The versions used in the Model 22 appear to have been drum-magazine types, but later models were belt-fed. The long-barrel type used in the Model 22a were known as the Model 2 Mark 3, and had a rate of fire of 490rpm with a muzzle velocity around 2000ft/see and a range up to l000m. The 30mm version, known as the Type 5, was fed from a 45-round magazine and had a muzzle velocity of 2460ft/sec.
Aiming was by means of a Type 98 reflector gunsight, and a Type 89 camera-gun could be fitted to the port wing root. A metal plate was found inside the fuselage of NZ6000, the inscription on it being translated as follows: '89 style Motion Picture Gun (Camera Gun) 2nd remodeled No/3899 Manufactured Roku Sakura Company'. This plate may relate to a camera gun fitted to this particular aircraft, or its presence may only be coincidental.