Published on
January 18, 2010 in
Japanese.
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.
SPECIFICATIONS
| 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)
Published on
January 17, 2010 in
Japanese.
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.
SPECIFICATIONS
| 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)
Published on
January 17, 2010 in
Japanese.
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.
SPECIFICATIONS
| 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 |
| 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)
Published on
January 16, 2010 in
Japanese.
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.
SPECIFICATIONS
| 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° |
| Depression |
|
7° |
| 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)
