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 18, 2010 in
Japanese.
This Japanese 20 mm aircraft gun is a modified version of the Model 97 antitank gun described on page 101. It is a gas-operated, full-automatic, magazine-fed, air-cooled weapon. The barrel, of monobloc construction, is fitted with a muzzle brake and attached to the receiver by means of a bushing of the interrupted screw type. The magazine fits into a rectangular opening in the top of the receiver, and the empty cartridge cases are ejected from a similar opening in the bottom. The ejector is secured to the underside of the receiver top just behind the magazine opening.
The operation of the aircraft version of this gun is similar to that of the antitank rifle. The six phases are: loading, locking, firing, unlocking, extraction, and ejection.
The first three occur on the counterrecoil, and the last three on the recoil. The gun is cocked the first time by pulling the retracting handle to the rear. This retracts the operating group to the position where the sear will engage the gas piston and hold it to the rear. After the magazine is inserted and locked in place, the gun is ready to fire.
The gun was mounted in the dorsal turret of the Bomber “Helen” on a semicircular-shaped rack, and is fixed to the rack by the lower left hand edge of the receiver. The rack is used for elevating the gun. The gun and mount are in turn mounted on the turret ring. The sight used on this gun is a reflector type sight and it is believed that there is provision made for deflection shooting. A fixed version has also been reported. Documentary evidence discloses that the ammunition for the turret gun is referred to as HO1 and the fixed as HO3.
SPECIFICATIONS
| Caliber |
|
20 mm (.79 in.) |
| Weight (without mount) |
|
74 lbs. |
| Length (with muzzle brake) |
|
68 7/8 ins. |
| (without muzzle brake) |
|
67 1/4 ins. |
| Sight radius |
|
|
| Principle of operation |
|
Gas |
| Capacity of feeding device |
|
Magazine, 15 rds.
Inverted saddle type, 50 rds. |
| Cooling system |
|
Air |
| Ammunition types |
|
AP/T; HE/T; HE/I; Ball |
| Rate of fire (estimated) |
|
300 rds. per min. |
| Type of sight |
|
Reflector |
| Weight of barrel |
|
|
| Length of barrel |
|
47 ins. |
| Length of rifling (approx.) |
|
42 ins. |
| Rifling |
|
|
| Twist |
| Form |
| No. of lands & grooves |
|
8 |
| Depth of grooves |
| Width of grooves |
| Chamber pressure |
| Muzzle velocity (estimated) |
|
2,500-2,900 ft. per sec. |
| Muzzle energy |
| Effective range |
|
1,000 yds. |
| Type of mount |
|
Dorsal turret and fixed |
Japanese: p. 253 (August 1, 1945)
Published on
January 18, 2010 in
Japanese.
This weapon, an improvement on the 12.7 mm Japanese copy of the U.S. Cal. .50 aircraft machine gun, is a recoil-operated, disintegrating metallic link belt-fed, air-cooled, aircraft machine cannon. It is mounted as a fixed weapon and as such it is fired electrically by remote control.
The recoil mechanism consists of a metal cylinder into which is fitted a coil spring. Through the center of this extends a 5/16-inch rod which screws into a brass bushing. The rod extends through the spring follower which rests on the coil spring and is secured by two lock nuts. Buffering action takes place in the recoil direction only. There is no quick change barrel. Because of the weight of the bolt and the heavy recoil spring, a booster is used, this being found in the flash hider.
The gun has a high cyclic rate of fire, muzzle velocities of 2,304 f/s (A.P.), 2,430 f/s (H.E.), and a penetration performance of 7/8-inch homogenous plate at 20° at 200 yards; 1/2-inch at 20° at 580 yards. The maximum weight lifting capacity of the belt is 62 pounds.
The disassembly of the weapon is the same as the Browning Cal. .30 and Cal. .50 machine guns with a few minor exceptions. The Japanese weapon has no back plate latch. The back plate is held in place by two pins, one at the top, and one at the bottom.
SPECIFICATIONS
| Caliber |
|
20 mm (0.79 in.) |
| Weight w/accessories |
|
104 11/16 lbs. |
| Weight w/o accessories |
|
86 3/4 lbs. |
| Length (overall) |
|
63 3/4 ins. |
| Sight radius |
| Principle of operation |
|
Recoil with muzzle cup |
| Feeding device |
|
Metal link belt type |
| Capacity of feeding device |
|
100 rounds |
| Cooling system |
|
Air |
| Ammunition types |
|
A.P., H.E., Incendiary |
| Cyclic rate |
|
950 r.p.m. |
| Type of sight |
|
Reflector |
| Weight of barrel |
|
12 1/8 lbs. |
| Length of barrel |
|
35.4 ins. |
| Length of rifling |
|
31.5 ins. |
| Rifling |
| Twist |
|
R.H. |
| Form |
| No. of grooves |
|
8 |
| Depth of grooves |
| Width of grooves |
| Chamber pressure |
| Muzzle velocity (A.P. Shot) |
|
2,304 f/s |
| (H.E. Shell) |
|
2,430 f/s |
| Effective range |
|
600 yds. |
Japanese: p. 252 (June 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
October 26, 2009 in
German.
The Mk. 108 A-3 is an automatic, air cooled, belt-fed weapon operated by blowback and firing electrically from an open bolt. Initial cocking and initial depression of the sear to release the bolt are accomplished by compressed air. The gun is mounted on its side, and fires through the propeller hub in ME 109 G fighters. It is attached at the forward end of the receiver to a blast tube which extends through the engine. This gun is unusual in being a blowback operated, low muzzle velocity weapon.
Sixty rounds of ammunition are fed by means of a disintegrating belt from an ammunition can mounted above the gun. On release of the sear, the bolt travels forward under the action of two driving springs. A projection on top of the bolt passes through the ring extracting a round and forcing it into the chamber. After firing the empty cartridge case reseats itself in its link. The ejection is accomplished by pawls actuated by camming grooves cut in the top of the bolt. Position of a new round takes place by the same action. A feature of the gun is the fact that the barrel and receiver do not move in recoil, the entire force of which is taken up by the rearward motion of the bolt against driving springs which act as buffers on recoil. There is no locking action between the barrel and bolt at any time.
All ammunition found to date has been high explosive, high explosive-tracer, incendiary and incendiary tracer. It is doubtful if the muzzle velocity is high enough for the effective use of armor piercing ammunition.
SPECIFICATIONS
| Caliber |
|
29.6 mm (1.17 in.) |
| Weight (total) |
|
265 lb. |
| Weight of gun |
|
136 lb. |
| Weight of mount |
|
28 lb. |
| Weight of ammunition can |
|
36 lb. |
| Weight of ammunition (60 rounds) |
|
65 lb. |
| Weight of recoiling parts |
|
24 1/2 lb. |
| Length of gun with blast tube |
|
7 ft. 6 3/4 ins. |
| Length of gun |
|
3 ft. 5 1/4 ins. |
| Length of barrel |
|
21 1/2 ins. |
| Number of lands and grooves |
|
16 |
| Maximum length of recoil of bolt |
|
11 1/2 ins. |
| Rate of fire |
|
500 rds./min. |
| Muzzle velocity (approx.) |
|
H.E.—1,650 f/s.* |
*Not verified
German: p. 255
