Tag Archive for 'type 99'

20 mm Aircraft Cannon Type 99 Mk. II

20 mm Aircraft Cannon Type 99 Mk. II

This is a gun of higher power than the Type 99 Mk. I, 20 mm cannon. Like the earlier gun, it operates on the Oerlikon principle and is found both with drum type magazine feed (Mod. III—top photo) and with belt feed (Mod. IV—lower photo).

The principal differences between this model and the Mk. I consist of a longer barrel and a longer chamber. The barrel protrudes 18 inches beyond the leading edge when mounted in the wings of fighter aircraft. The projectiles used are identical to the Mark I, but the cartridge employed contains approximately 40% more propellant than the older type, thereby increasing the velocity of the Mk. II 500 to 700 foot seconds. The muzzle velocity of the weapon varies from 2,500 to 2,700 foot seconds depending upon the type of projectile used. The gun has been found in ZEKEs and HAMPs. It is probably fitted in RUFEs and as a flexible gun in the tail turret of BETTY.


Caliber         20 mm (.787 in.)
Weight of gun 67 lbs.
Length of gun (overall) 73 ins.
Length of barrel 47 ins.
Length of rifling 41.5 ins.
Number of grooves 9
Depth of grooves 0.026 in.
Twist of rifling Right hand
Principle of operation Blow back
Feeding device French drum or belt
Capacity of drum 100 rds.
Cooling system Air
Sights Reflector type
Charging mechanism Pneumatic
Firing system Flexible cable
Effective range (est.) 600-700 yds.
Rate of fire (est.) 400-500 r.p.m.
Ammunition Ball, A.P., A.P./I., T., H.E., H.E./T., H.E./I.

Japanese: p. 254 (August 1, 1945)

20 mm Aircraft Automatic Cannon, Model 99 Mk 1 Flexible

20 mm Aircraft Automatic Cannon, Model 99 Mk 1 Flexible

This weapon is an air-cooled, blowback-operated, Oerlikon type machine cannon. It operates on the same basic principle as all Oerlikon cannons of this type. The Japanese gun is a close copy of the Swiss gun, in that it is designed for full automatic fire only. The gun is manufactured in Japan on Swiss machinery. The above illustration shows the flexible version.

A significant feature is that the parts which are subjected to little wear, such as the grips, mounts, gunners’ shoulder rest, and other exterior parts are generally made of light weight metal.

This weapon is almost identical with other Model 99 (1939), 20 mm aircraft cannon reported to be used in the majority of Japanese planes, both as fixed guns in fighter craft, and as flexible guns in bombing planes. The weapon is fed from a drum type magazine. It is cocked or charged by manual means, and has no semiautomatic charger or rounds counter. The cocking handle is rotated to draw the recoiling parts to the rear and cock the gun for the first shot, the gun firing from an open bolt. Cocking operations for succeeding shots are performed by the blowback operation of the gun itself.


Caliber         20 mm—0.87 ins.
Weight (without magazine) 62 lbs.
Weight of 60 rd. magaine (empty) 20 lbs.
Length (overall) 55 ins.
Length of barrel 30 ins.
No. of grooves 9; Uniform right hand twist
Width of grooves
Depth of grooves 0.022 in.
Width of lands
Muzzle velocity (shell) 1,930 f/s.
Cyclic rate 510 r.p.m.
Traverse Flexible aircraft
Length of recoil
Turns of cocking handle required to cock piece 11 1/2 ins.
Ammunition HE; HE with tracer; HE with self-destroying tracer; HE-I; AP; AP tracer; AP-HEI; Long burning tracer; Practice
Wt. of HE projectile 4.50 ozs.
Type of feed 60 rd. drum

Japanese: p. 251 (June 1, 1945)

7.7 mm Paratrooper Rifles

Japanese 7.7 mm Paratrooper Rifles

Both of the weapons shown above are basically the same as the Japanese 7.7 mm standard infantry rifle, Model 99. They have been designed, however, to incorporate a takedown feature which enables them to be used by paratroop units. Manufactured at Nagoya Arsenal, they are manually-operated, bolt-action, magazine-fed, clip-loaded rifles.

The modified Model 99 differs from the basic weapon in the following respects: the barrel locking adaptor is secured to the receiver; the barrel is secured into the adaptor by interrupted screw threads; the bolt handle is detachable; and the stock is in two parts.

The Model 2, called “Teraju” by the Japanese, is of much better workmanship than the Modified Model 99. The barrel and front end are detached from the stock at the receiver ring. When taken down, the barrel section is 25 1/2 inches long; the stock 20 1/4inches. Total weight of the loaded weapon is 8.9 pounds. The takedown system is simple and sturdy. The barrel has a straight, unthreaded shank with a lug on the bottom. The shank fits into a socket in front of the receiver. A tapered locking key passes through the receiver (from right to left) and engages in front of the barrel lug. The key cannot be taken out completely, but may be withdrawn far enough to allow removal of the barrel. It is locked in place by screwing a nut on the right side into the receiver wall.

A spring actuated plunger located in the front end of the buttstock locks the barrel and forestock in position. This plunger must be retracted before the barrel can be rotated for takedown.


Weight        8.9 lbs.
Length 44″
Principle of operation Manual, bolt-operated
Feeding device Clip
Capacity of feeding device 5 rounds
Ammunition types Model 99 rimless
Type of sight Front: inverted “V” blade on “T” base; Rear: leaf graduated from 328 to 1,640 yds. with aperature sight and aperture battle sight side arms for A.A. fire.
Weight of barrel
Length of barrel 25 7/8″
Length of rifling
   Twist Uniform, right hand; one turn in approx. 10 ins.
   Form Metford segmental
   No. of grooves 4
   Depth of grooves
   Width of grooves
Chamber pressure
Muzzle velocity 2,360 f/s
Maximum range 3,000 yds.
Effective range 600 yds.

Japanese: p. 212.1 (May 1, 1945)

88 mm Antiaircraft Gun Type 99

Japanese 88 mm Antiaircraft Gun Type 99

This weapon which was recovered at Rangoon has a barrel of monobloc construction, machined to take a rectangular breech ring. A large threaded brass locking collar holds the breech ring in position. Rifling is right hand twist. The breech mechanism is semi-automatic of the vertical sliding type; the firing mechanism is a percussion type.

The piece fits in a sleeve type cradle to which are fitted the buffer cylinder, the recuperator cylinders, the trunnions, and the elevating arc. The recoil mechanism is hydropneumatic. Two recuperator cylinders are located one on each side of the recoil cylinder which is centrally mounted above the piece. The elevating arc is mounted under the piece offset slightly to the left. It is operated by a handwheel and crank on the left of the gun, and like the traversing handwheel, on the right of the gun, is forward of the trunnions.

The upper carriage consists of two side plates joined by three cross members, and revolves on a ball race fitted to its base. A pintle, bolted to the center of the base, extends down into a bearing in the pedestal. Three brackets are set at regular intervals around the upper carriage to prevent lateral play. The pedestal is a single cast truncated cone, reinforced internally and externally by six ribs. Twelve bolts secure it to a circular steel base plate.

Follow-the-pointer dials are provided for azimuth, elevation, and fuze setting. Three mechanical fuze-setters are also provided. Some of the guns examined were equipped with open sights of very primitive design.


Caliber         88 mm (3.5 ins.)
Weight (complete) 14,560 lbs.
Weight of cradle 1,256 lbs.
Weight of carriage (including elevating & traversing mech.) 4,894 lbs.
Length (traveling position)
Length of barrel assembly 255.8 ins.
Height (traveling position)
Height (firing position)
Width (overall)
Length of bore
No. of grooves 32
Width of grooves
Depth of grooves 1 mm
Width of lands
Muzzle velocity (shell) 2,650 f/s
Max. range (horizontal)
Max. range (vertical)
Rate of fire
Traverse 360°
Elevation 80°
Length of recoil (approx.) 14-15 ins.
Ammunition H.E.
Wt. of projectile (H.E.) (approx.) 18 lbs.

Japanese: p. 114.2 (August 1, 1945)