JPN - Type 99-1 Model 1 a 2 (20 mm kanon)

九九式二〇粍一号機銃一型 / 二型
Autocannon Type 99-1 Model 1 and Model 2 Autocannon Type 99 Mark 1 Model 1 and Model 2
Original Title:
Original Name: 九九式二〇粍一号機銃一型 / 九九式二〇粍一号機銃二型
Dai Nihon Heiki K. K., Toykawa Naval Arsenal
Period of production:
Production Period:
Units produced:
Number of Produced:
Prototype Produced:
Prototype Built:
Micubishi A6M2, G3M, G4M, Kawanishi H6K, H8K, Nakajima J1N
 Technical Data:
Weight: 23 kg51 lb
20 mm / 0.79 in
Barrel Length:
Barrel Length:
800mm2ft 7.5in
Overall Length:
Overall Length: 1331mm4ft 4.39in
Ammunition Used:
Ammo Used:
Bullet (124g), Armor Piercing (129g) Armor Piercing Incendiary, Tracer, Tearing, Tearing with Tracer, Tearing Incendiary and Incendiary Ball, AP (4.5 oz), API, T, HE, HET, HEI, I
Maximum Range:
Maximum Range:
0.8 - 1 km0.5 - 0.6 mi
Rate of Fire:
Rate of Fire:
520 rpm 520 rpm
Rate of Attack:
Muzzle Velocity:
600 m/s 1968.5 ft/s
九式一号機銃 - Kyū-Kyū Shiki Ichigō Kizjū, Kanji - 20mm gun type 99-1

This gun was produced in both fixed and mobile mount versions.
The fixed mount version was adopted first and first appeared in the A6M fighter Micubish, later a movable version was adopted and installed in the G3M bomber, this version was rotated 180° compared to the fixed mount gun - the drum magazine was under the gun. Depending on the space in the turret / firing range, magazines for 15, 30, 45 and 60 shells were used.
Other versions:
60 grenades for a fixed gun was not enough, so a large drum magazine for 100 grenades was used in the Type 99-1 Model 3, but the size of the drum was already a problem for the fighter's wing mount.
This problem was eliminated by the Type 99-1 Model 4 cartridge belt.

The Type 99-1 naval air gun was a modified copy of the Swiss Oerlikon FF-F.
Kyū-Kyū Shiki Ichigō Kizyū, Kanji: 九式一号機銃

The Navy cannon Type 99-1 was adopted by the Japanese Navy for both fixed and flexible installations.
First adopted was the fixed installation, for fighter aircraft, this gun fed by a 60-round drum magazine and mounted in the wings of the Mitsubishi A6M.
A flexible version, developed for the Mitsubishi G3M bomber, was inverted to put the ammunition drum below the line of sight of the gunner.
Smaller drums (15, 30 or 45 rounds) were used on flexible mounted where was little space.
The Type 99-1 Fixed Model 3 could be equipped with a 100-round drum, but the size of the drum was itself a problem in fighter installations, although the Model 3 guns were installed on the initial production versions of the A6M3. A more practical solution was provided by the Type 99-1 Fixed Model 4, which featured a Kawamura-developed belt feed mechanism.

It was a copy of the Swiss Oerlikon FF-F cannon.
René J. Francillon Ph.D., Japanese Aircraft of the Pacific War, Naval Institute Press, Annapolis Maryland, Reprinted 1990, ISBN-0-87021-313-X
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The image of the movable cannon Type 99 Model 1, used on the bomber Mitsubishi G4M Betty.
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