Tag: 20mm

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German

2 cm Flak 38: A.A./A.T. Gun

2 cm Flak 38: A.A./A.T. Gun

The Flak 38 was introduced in 1940 to replace the 2 cm Flak 30. Its performance does not differ materially from that of the earlier weapon, except for a higher cyclic rate of fire of 450 rounds per minute.

The gun is operated by short barrel recoil and the residual pressure of gas in the barrel. Recoil unlocks the breech and imparts rearward acceleration to the breechblock carrier. This rearward acceleration is assisted by gas pressure after unlocking has been completed so that the breechblock travels back with sufficient force to perform the operations of extraction, ejection, and compression of the return spring.

The energy required for closing the breech and carrying a fresh round to the chamber is provided by the return spring, assisted at first by the buffer spring.

The breechblock is of the Solothurn type. Any tendency toward rebound is counteracted by the impact of an inertia block at the end of the forward movement. The barrel has resistance rings which brake the recoil and forward movements of the barrel; a buffer and buffer spring arrest the backward movement of the breech block.

This weapon may be adjusted for either semi-automatic or full-automatic fire. It is fired by a foot pedal. Cartridges are fed from a 20-round curved box magazine hinged on the left of the gun.

The mounting consists principally of the base, cradle, traversing and elevating gears, firing mechanism, and lighting equipment.

Traverse is 10° per turn of handwheel in fine gear and 30° in coarse gear; rate of elevation or depression is 4° per turn in fine gear and 12° in coarse gear.

The weapon, which is transported on a trailer, may be mounted on railways cars or road vehicles. When traveling over difficult country, gun and mounting may be split into six loads.

SPECIFICATIONS

Caliber         20 mm (.79 in.)
Length of tube
Weight (travelling position) 1,630 lb.
Weight (firing position) 924 lb.
Length (travelling position) 157 ins.
Height (travelling position) 67 ins.
Height (firing position) 30 ins. mounted flush
Width (overall) 71 ins.
Width of trail spread
Length of bore 44 ins.
No. of grooves
Width of grooves
Depth of grooves
Width of lands
Muzzle velocity (HE shell) 2,950 f.s. (A.P. shell)
2,624 f.s.
Max. range (horizontal) 5,246 yds.
Max. range (vertical) 4,012 yds.
Rate of fire 220 rds. (practical), 450 (theoretical)
Traverse 360°
Elevation +90°
Depression -20°
Length of recoil
Ammunition H.E. four types; A.P. two types
Wt. of 1 magazine of 20 rds 21 lb.

German: p. 136

Categories
German

2 cm Flak 30: Antiaircraft Gun

2 cm Flak 30: Antiaircraft Gun

The Flak 30 was the principal armament of German light antiaircraft units since the beginning of the war in Europe until the introduction of the 2 cm Flak 38 and 2 cm Flak 38 Vierling. The gun, which may be mounted on road or railway vehicles, is normally transported on a single-axle trailer which is drawn by either horse or motor vehicle. It is usually fired with its mounting on the ground and with the trailer removed. However, it can be fired from the trailer at both ground or aerial targets in emergencies.

This recoil-operated weapon is fed by a flat 20-round box magazine. The trigger mechanism is pedal-actuated; operation is either full-automatic or semi-automatic.

The barrel slides in the body with the barrel extension. A combined muzzle brake and flash eliminator is screwed to the muzzle and retained by a catch. The barrel extension is slotted on the right and left sides for ejection and feed respectively.

The body is formed to receive the barrel extension, which is hinged near the rear end of the body. The barrel return spring, buffer spring, buffer, and rod and sleeve are housed in a casing secured to the body at the rear.

The sights used are the Flakvisier 35, and the Linealvisier 21, the former is of the reflecting-mirror type with a data-calculating mechanism; the latter is a direct antiaircraft sight embodying course, speed, and range adjustment.

The gun carriage consists of a firm under carriage and a revolving top carriage supported on ball bearings. The under carriage is leveled by three adjustable feet, and is provided with a spirit level. The top carriage has a cradle which is adjustable for elevation. The elevation handwheel is located on the right side of the top carriage, and the traversing handwheel at the back.

SPECIFICATIONS

Caliber         2 cm (.79 in.)
Length of tube
Weigth (travelling position) 1,697 lb.
Weight (firing position) 992 lb.
Length (travelling position) 160 ins.
Length (firing position)
Height (travelling position) 63 ins.
Height (firing position) 29 ins. mounted flush
Width (overall); (travelling position) 72 ins.
Width of trail spread
Length of bore
No. of grooves
Width of grooves
Depth of grooves
Width of lands
Muzzle velocity (H.E. shell) 2,950 f.s.
(A.P. shell) 2,624 f.s.
Max. range (horizontal) 5,246 yds.
Max. range (vertical) 4,012 yds.
Rate of fire 120 practical; theoretical 280
Traverse 360°
Elevation +90°
Depression -10°
Length of recoil
Ammunition H.E. (four types); A.P. (two types)
Wt. of 1 magazine of 20 rds 21 lb.

German: p. 135

Categories
German

2 cm Flak 38 Geb.: A.A./A.T. Mountain Gun

Gebirgsflak 38: 2 cm Flak 38 Geb.: A.A./A.T. Mountain Gun

The 2 cm Flak 38, used in mountainous territory, is a semi- or full-automatic, short recoil operated gun. It is fed with a box type magazine containing 20 rounds. The breechblock is of the Solothurn type. The barrel is equipped with a flash hider. It is the 2 cm Flak 38 gun on a light mount.

This weapon is fired by means of a foot pedal on the right front of the mount. The layer’s seat behind the gun rotates with the mount in traverse. Elevating and traversing are manual by means of handwheels located on the right and left sides of the mount respectively. There are two speeds both in elevating and traversing; high speed is obtained by compressing a lever in the handwheel grip.

A small shield is attached to the front of the cradle, and a large shield of two sections is attached to the front of the mount. This mount is a two-wheeled, pneumatic-tired trailer and pack type which may be towed by a prime mover or taken apart and transported in sections by horse or foot troops.

SPECIFICATIONS

Caliber         20 mm (.79 in.)
Length of tube (with flash hider) 56.6 ins.
Weigth (travelling position) 825 lb.
Weight (firing position) 690 lb.
Length (travelling position) 143 ins.
Length (firing position)
Height (travelling position) 50-57 ins.
Height (firing position) 31-42 ins. mounted flush
Width (overall); (travelling position) 47 ins.
Width of trail spread
Length of bore 44 ins.
No. of grooves
Width of grooves
Depth of grooves
Width of lands
Muzzle velocity (H.E. shell) 2,950 f.s.;
(A.P. shell) 2,624 f.s.
Max. range (horizontal) 5,246 yds.
Max. range (vertical) 4,012 yds.
Rate of fire 220 yds. (practical): 450 (theoretical)
Traverse 360°
Elevation +90°
Depression -20°
Length of recoil
Ammunition H.E. (four types): A.P. (two types)
Wt. of 1 magazine of 20 rds 21 lb.

German: p. 137

Categories
German

2 cm Flakvierling 38: A.A./A.T. Gun

2 cm Flakvierling 38: A.A./A.T. Gun

The 2 cm Flakvierling 38, consisting of four 2 cm Flak 38’s on a quadruple mounting, may be employed against both ground and aerial targets. It is normally transported on a trailer (Sd. Ah. 52) but may be mounted on railed or semi-tracked vehicles. The Trailer 52 consists of a wishbone-shaped, welded 1/4 inch steel plate frame supported on pneumatic tires. Because of its collapsing seats, folding handles, and handy ammunition racks, the Flakvierling 38 is a trim, compact, and conveniently operated weapon. The monobloc barrels may be quickly and easily changed, and the piece rapidly emplaced for fire.

The method of operation is basically that of the Solothurn. Both barrel and bolt recoil a short distance together; the barrel stops, and the bolt continues on to the rear. The guns fire from an open bolt position and may be operated either automatically or semi-automatically. Each one is equipped with a spring type equilibrator that is attached to the mount.

The mount consists of a triangular base which has a jack at each apex for leveling the gun when it is in firing position; a traversing ring which is fixed to the base and upon which the carriage body sits; and the carriage body, which in turn supports the four barrels and accessories. A compensator bolted to the carriage body counteracts muzzle preponderance.

The guns are fired by a set of foot pedals; each of two pedals fires two diametrically opposite guns. The mount is traversed and elevated manually by the tracker who has the two handwheels within easy reach. Empty cartridge cases are ejected toward the center of the gun mount into chutes leading to a deflector box which holds about 500 cases.

Sighting equipment for the Flakvierling 38 consists of the tachymetric sight, Flakvisier 40, or for ground targets, the Linealvisier 21.

SPECIFICATIONS

Caliber         2 cm (.79 in.)
Length of tube 45.82 ins. plus flash hider of 5.75 ins.
Weight (travelling position) 4,890 lb.
Weight (firing position) 3,200 lb.
Length (overall) 169 ins.
Length (firing position)
Height (travelling position) 84 ins.
Height (firing position) guns elevated 10 ft., 1 in.
Width (overall), (travelling position) 95 ins.
Width of trail spread
Length of bore
No. of grooves 8 lands and grooves
Width of grooves
Depth of grooves
Width of lands
Muzzle velocity (H.E. shell) 2,950 f.s.
(A.P. shell) 2,624 f.s.
Max. range (horizontal) 5,246 yds.
Max. range (vertical) 4,012 yds.
Rate of fire 800 practical; 1,400 cyclic rds. per min.
Traverse 360°
Elevation 100°
Depression -10°
Length of recoil
Ammunition H.E. four types; A.P. two types
Wt. of 1 magazine of 20 rds 21 lb.
Ammunition stowage 320 rds.

German: p. 133

Categories
German

20 mm M.G. 151/20 (Mauser): Aircraft Machine Gun

20 mm M.G. 151/20 (Mauser): Aircraft Machine Gun
The M.G. 151/20 mm and M.G. 151/15 mm (Mauser) were designed and built by the famous Mauser factory. The M.G. 151/20 is a fixed aircraft cannon, recoil-operated and belt-fed, using a disintegrating metallic link belt. It was manufactured also in a 15 mm form. Although the receiver group and the recoiling portions are not identical, the superficial appearance of the two guns is very similar.

Two of these guns are mounted in each of the Focke-Wulf FW 190 types of planes. In this installation, they are synchronized, firing through the propeller arc. They are installed in the wing roots about 12 inches out from the engine cowling with the barrels protruding about 2 feet beyond the leading edge.

This gun is electrically cocked and fired, and electric detonation of the cartridge has been adopted in order to facilitate interruption when it is used as a synchronized gun. A longer-barreled version with mechanical detonation is used when the gun is mounted to fire through the propeller hub as in the ME-109.

In the version mounted in the fuselage, the feeding device has a capacity of 50 rounds, but more rounds are usually carried for each gun when it is wing mounted. A streamlined container holds the gun and the belted ammunition in newer installations.

The following types of ammunition are used in the 20 mm version: H.E. with S.D. fuze; H.E.I./T. with S.D. fuze; A.P.I., A.P.H.E., and two different H.E.I. (S.D. fuze) rounds.

SPECIFICATIONS

Caliber         20 mm (.787 in.)
Weight including electric control 93 1/2 lb.
Weight of barrel 22 lb., 14 oz.
Overall length 69 1/2 ins.
Length of barrel 43 1/2 ins.
Principle of operation Short recoil, no muzzle recoil booster, rotating bolt head
Cooling system Air
Feeding device Disintegrating metallic link belt
Capacity of belt 50 rds. and multiples thereof
Muzzle velocity (H.E.) 2,656 f/s
Rate of fire 780 r.p.m.
Ammunition used H.E. with S.D. fuze; H.E.I./T. with S.D. fuze; A.P.I.; A.P.H.E.; and two different H.E.I. (S.D. fuze) rounds.

German: p. 252

Categories
German

20 mm M.G. F.F.M. (Oerlikon): Aircraft Machine Gun

20 mm M.G. F.F.M. (Oerlikon): Aircraft Machine Gun

This flexible 20 mm aircraft machine gun, Oerlikon M.G. F.F., is the German Air Force version of the Swiss Oerlikon 20 mm machine gun.

The weapon is a blowback, inertia-operated, air-cooled machine gun for fixed or flexible mounts. It fires from an open bolt and has an electrically operated trigger mechanism. The cartridge-counting mechanism is also electrically operated. It has a pneumatic charging mechanism to retract the bolt for the first shot.

Some minor modifications of the Swiss version of this machine gun have been introduced. It is chambered to fit the short German 20 mm round, and the travel of the recoiling parts has been redesigned to conform. The barrel has been shortened and the gun lightened considerably. It has been in use in this form without material alteration since the beginning of the war.

The gun was originally intended as a fixed weapon and was termed the M.G. F.F. A later type, the F.F.M., is mechanically the same but in some cases is provided with a cooling cowling and a hand firing device for use as a free gun. It is used both as a flexible and a fixed gun.

SPECIFICATIONS

Caliber         20 mm
Weight 76 1/2 lb.
Length 57 ins.
Feed Drum—60 rd. capacity
Length of barrel 32 1/4 ins.
Cooling Air
Operation Blowback (inertia) with solenoid trigger
Fire Automatic only
Rate of fire 450 to 500 rds./min.—cyclic

German: p. 251

Categories
German

2 cm s PzB (Solothurn s/8-1100): A.T. Gun (Ex-Swiss)

2 cm s PzB (Solothurn s/8-1100): A.T. Gun (Ex-Swiss)

This gun, an improved version of the Solothurn 1933 model manufactured in Switzerland by the Waffenfabrik, is a magazine fed, recoil operated, semi-automatic shoulder weapon which can be fired from a bipod or a low-lying, pneumatic-wheeled carriage. The combined weight of gun and mount is approximately 200 pounds; the gun itself weighs 103 pounds.

The barrel is easily changed by giving it a half turn, thereby disengaging two lugs. Two types of magazines are used; one holding five rounds and the other ten.

The bolt is forward and all parts rigid when the firing pin strikes the cap of the projectile. When the last shot in the magazine is fired, the cartridge case is automatically ejected; then when a new magazine is inserted, the bolt is again thrown forward automatically and the gun is ready to fire.

Construction of all parts is exceptionally rugged and simple. The gun, which fires semi-automatically, is extremely accurate and easily handled. In comparison with the earlier model, the new gun shows a slight decrease in weight, increased muzzle velocity, and high armor-penetrating qualities. It also possesses the advantage of a dust-proof breech mechanism.

SPECIFICATIONS

Caliber         20 mm (.79 in.)
Weight of gun (complete) 103 lb.
Weight of barrel with muzzle brake (approx.) 44 lb.
Length of gun (overall) 7.1 ft.
Length of barrel 4.25 ft.
Rifling 8 lands and grooves; 5° uniform twist
Muzzle velocity (reported) 937-991 yds./sec.

German: p. 134

Categories
German

2 cm Flak (Madsen): A.A./A.T. Gun (Ex-Danish)

2 cm Flak (Madsen): A.A./A.T. Gun (Ex-Danish)

The Madsen 20 mm automatic antiaircraft and antitank gun, a Danish weapon used largely by the German Navy, is also in service in the Bulgarian, Finnish, Hungarian, Portuguese, and Spanish armies. This rapid-fire model is a heavy-caliber, air-cooled, recoil-operated cannon, which is much more sturdy than the ordinary Madsen.

The fixed parts of the gun comprise the barrel casing with the sights, the frame with the magazine receiver, and the trigger plate with the trigger device. Recoiling parts comprise the barrel, the breech, and the breechblock. The connection between the fixed parts and the recoiling parts is established by means of the recoil arm and the link of the breech, together with the return mechanism.

The muzzle of the barrel is threaded externally to take the muzzle brake, and at the chamber to fit into the breech. It is secured to the breech by a locking pin. The oblong breech has an elongated opening in its left wall to accommodate the 60-round drum magazine feeding device.

The trigger mechanism can be set for either single-shot or automatic firing by means of a change over swivel.

The sighting gear, placed on the upper side of the barrel casing, consists of a leaf rear sight graduated from 100 to 1,800 m, and can be set in accordance with the graduations by means of the rear sight slide.

The cannon employs a universal mount.

SPECIFICATIONS

Caliber         20 mm (.79 in.)
Weight in action 390 lb.
Weight of cannon 119 lb.
Length of cannon (overall) 7.38 ft.
Length of barrel 3.94 ft.
Rifling 10 lands and grooves; 5° twist
Rate of fire (practical) 200 rds./min.
Muzzle velocity 2,950 f/s
Range 6,015 yds.
Effective ceiling 6,960 ft.
Elevation 85°
Depression -5°
Traverse 360°
Ammunition H.E.; A.P.

German: p. 132

Categories
Japanese

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.

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)

Categories
Japanese

20 mm Aircraft Machine Gun (Modified Model 97 Antitank Gun)

20 mm Aircraft Machine Gun (Modified Model 97 Antitank Gun)

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)