Flying Guns: Post-War Fighters

After WWII

The first jet fighters were developed during WWII: The Heinkel He 280, Messerschmitt Me 262, Heinkel He 162, Gloster Meteor, de Havilland Vampire, Lockheed P-80, and McDonnell FH Phantom. Their advantages were so obvious that only a handful of propeller-driven fighters entered service after the war.

The number of people at work in one picture strongly suggests that it was staged. But it illustrates how the four Hispano cannon were installed in the Meteor.

Jet fighters brought higher speeds, and that in itself made gun aiming more difficult. To cope with the aerodynamic forces at higher speeds, the structure of the aircraft became sturdier, with thicker skins. All this increased the need for powerful armament. On the other hand radar equipment, better gunsights and later head-up displays promised to make guns far more accurate. At first the electronics systems were maintenance-intensive and poorly suited to the stress of combat, but the sophistication of today’s aircraft is such that any round fired has a high probability to hit the target.

The armament of the first jet fighters was fundamentally the same as that of the last piston-engine fighters. There was only a change in armament installation: Most jet fighters had their guns in the nose. Installing guns in the nose instead of the wings gave concentrated fire at a wide range of distances. The nose also offered more room than the wings, which were being made thinner to reach higher speeds. And putting the guns in front helped to balance the weight of the jet engine in the tail. A problem, especially for night operations, is the muzzle flash, that might blind the pilot temporarily.

While Germany did not continue to build military aircraft after the defeat in 1945, it is interesting to have a look at the designs that were on the drawing boards. These were eagerly studied by the victorious allies, and inspired many post-war aircraft. The Luftwaffe initially demanded that the replacement of the Me 262 would be a high-altitude jet fighter capable of 1000km/h between 7000m and 9000m, and with an endurance of 60 minutes at full throttle. The pilot had to be put in a pressure cabin, with sufficient armour to stop .50 ammunition. Initially, the Luftwaffe was satisfied with two 30mm MK 108 cannon. But it quickly upgraded its demands to four MK 108 cannon, and two hours endurance. The proposals were all swept-wing jet fighters. Alternatives to the four MK 108 cannon proposed by the designers included two MK 103 and two MG 151/20 cannon, or two MG 213C revolver cannon.

The MG 213C was designed in 1944, and it was a revolver gun with a five-chamber cylinder. By dividing the loading of a cartridge in three steps, a high rate of fire could be achieved while keeping the forces within the gun limited. There were 20mm and 30mm versions. The MG 213C made linear action guns largely obsolete for fighters, and was copied widely.

Name Ammunition Rate of FireMuzzle velocityWeight Q-factor
MG 213C/20 20 x 135
(112 g) 
1400 rpm 1050 m/s 75 kg 19200
MG 213C/30 30 x 85B
(330 g) 
1200 rpm 530 m/s 75 kg 12400
BK 27 27 x 145 B
(260 g) 
1700 rpm 1025 m/s 100 kg 38700
Aden Mk.4 30 x 113
(220 g) 
1300 rpm 790 m/s 87 kg 17100
Aden 25 25 x 137
(180 g) 
1750 rpm 1050 m/s 92 kg 31500
KCA 30 x 173
(360 g) 
1350 rpm 1030 m/s 136 kg 31600
DEFA 554 30 x 113
(275 g) 
1800 rpm 820 m/s 80 kg 34700
GIAT 30M791 30 x 150
(275 g) 
2500 rpm 1025 m/s 110 kg 54700
M39 20 x 102
(101 g) 
1700 rpm 1030 m/s 81 kg 18700
Revolved Cannon

Initially, in Britain the armament of four 20mm Hispano cannon remained the standard. The Meteor had actually been designed for six such cannon, but the mounting of two of them was too unpractical to be safely used. The Hispano remained in use until the first swept-wing fighters appeared with the 30mm Aden cannon, a copy of the MG 213C. With four Aden guns, the Hawker Hunter was considered over-gunned by many observers: A rare distinction for any fighter aircraft. Two Aden guns, as in the Lightning, Jaguar, Saab J35 Draken, and Folland Gnat, was a more common armament.

The evolution in France was almost identical to that in Britain, except that the Hispano was not replaced by the Aden but by the DEFA, a French derivative of the MG 213C. The Aden and DEFA guns initially used slightly different ammunition, but later common ammunition was introduced, creating a de facto standard for 30mm rounds. Because of the successful export of French aircraft, the DEFA gun is still used world-wide. The later developments had an increased rate of fire (up to 1800 rpm) and are fitted to modern fighters such as the Mirage 2000.

Sweden adopted the Swiss 30mm Oerlikon KCA, a very powerful revolver cannon, for the Saab JA 37 Viggen interceptor. It is relatively slow-firing, but has excellent ballistics and it has been estimated that its ammunition has twice the destructive power of the Aden/DEFA ammunition of the same calibre.

The US Navy initially followed the British example. This had already begun during the war, with types such as the F4U-1C and F8F-1B. Its first jet fighters almost all had four 20mm Hispano cannon, for example the FH Phantom, F2H Banshee, and F9F Panther. The M3 version of this gun was boosted to 850rpm. Like the Hispano Mk.V, it had been lightened by shortening the barrel, in this case by 15in. The USN was unusual in that it continued the use of linear-action weapons on swept-wing fighters and right into the supersonic age, although in an upgraded version: The Colt Mk.12. The Mk.12 fired a lighter projectile with a larger charge. But on the Navy’s Mach 2 fighter, the Vought F8U Crusader, the Colt guns were an anachronism. They had a good rate of fire and a high muzzle velocity, but were inaccurate, unreliable, and unpopular. But the F8U at least had guns, and they contributed to the good reputation that this fighter acquired in Vietnam. No gun was installed on the F-4 Phantom II, in part because the belief that guided missiles would result in combat being fought at ranges beyond that of guns, but also because the weight, bulk and vibration of guns were undesirable in aircraft that had to find room for a lot of fragile electronics. Experience in Vietnam indicated that it was still highly desirable to have a gun, and currently USN fighters are equipped with the six-barrel M61 Vulcan.

Name Ammunition Rate of FireMuzzle velocityWeight Q-factor
Colt Mk.12 20 x 110
(110 g) 
1000 rpm 1010 m/s 46 kg 20300
AM-23 23 x 115
(200 g) 
950 rpm 690 m/s 39 kg 19300
NS-23 23 x 115
(200 g) 
550 rpm 690 m/s 37 kg 11800
NR-23 23 x 115
(200 g) 
950 rpm 690 m/s 39 kg 19300
NR-30 30 x 155B
(410 g) 
900 rpm 780 m/s 66 kg 28300
N-37 37 x 155
(755 g) 
400 rpm 690 m/s 103 kg 11600
GSh-30-1 30 x 165
(400 g) 
1800 rpm 890 m/s 46 kg 103000
Linear action guns.

The USAF was even more conservative. In the late 1940s the standard armament of USAF fighters, with only few exceptions, was still six Browning .50 M3 guns. The M3 had a higher rate of fire than the M2 version used in WWII, but experience in Korea demonstrated that this armament was painfully insufficient. A report by Colonel Eagleston estimated that two thirds of all MiG-15s hit with the .50 guns escaped. On the other side it was observed that MiG-15s with 40 or 50 hits routinely returned home. The American pilots still held the advantage, because of better training, better gunsights, and generally better equipment.

In some nightfighters and fighter-bombers the USAF installed the 20mm M24 cannon, a version of the Hispano M3 of the US Navy, modified to use electrically primed ammunition. The first versions of the F-89 Scorpion, for example, carried six of these guns. The F-86K carried four.

It’s only a mock-up: For tests, six M24 Hispano cannon were installed in a mock-up of the nose of the XF-88.

A much-needed improvement was the Pontiac M39, a 20mm revolver cannon broadly based on the MG 213C, but almost entirely redesigned. This far better weapon was installed on fighters such as the F-86H Sabre, F-100 Super Sabre, and Northrop F-5. A switch to 30mm cannon was considered, but rejected in the belief that guided missiles would soon make the cannon obsolete. Apparently, two F-89C protototypes were the only US fighters that ever carried 30mm cannon.

The F-4 and F-106 appeared without cannon, but like the USN the USAF had to change its mind because of combat experience, and during the Vietnam war cannon were installed in these fighters. The standard weapon became the six-barrel M61 Vulcan, and it is still in use today, usually in its M61A1 form. The M61 was the first rotary cannon, generally (and not entirely correct) called a Gatling gun. Such weapons are reliable and offer a very high rate of fire, and by dividing the firing over several barrels their wear is reduced. Of course such guns weigh more than single-barrel weapons. Characteristic of the M61A1, and most US rotary cannon, is the beltless feed mechanism: Rounds are transported on a kind of conveyer belt system, and empty cases are transported back into the drum. The original M61 had a belt feed, but this could not take the strain of firing rates higher than 4000 rpm.

An objection raised against rotary cannon is that the spin-up time is fairly long: It takes 0.4 sec before the M61A1 spins up to its nominal rate of fire, while a revolver gun reaches its nominal rate of fire after 0.05 sec. Hence the advantage of the rotary cannon is minimal or non-existent during a short burst. It somewhat depends, however, on the power source of the rotary gun.

Name Ammunition Rate of FireMuzzle velocityWeight Q-factor
M61A1 20 x 102
(101 g) 
6600 rpm 1035 m/s 120 kg 49600
GSh-6-23 23 x 115
(200 g) 
8000 rpm 740 m/s 76 kg 96100
GSh-6-30 30 x 165
(400 g) 
5400 rpm 850 m/s 145 kg 89700
Rotary guns.
The N-37

The Soviet Union was more reluctant to abandon its guns, and it indeed developed a surprisingly large number of new ones in the post-war years. Apparently the USSR was reluctant to copy the MG 213C. It did show a preference for large-calibre weapons, with calibres up to 57mm proposed for installation in fighters. In these early years of the Cold War only the USA had nuclear weapons, and the only means to deliver these bombs was the B-29 or B-50 bomber. Hence Soviet fighters were given armament sufficiently powerful to shoot down B-29s. The first Soviet jet fighter, the MiG-9, was designed for two 23mm NS-23 cannon and one 57mm N-57, but the latter was replaced by the less ponderous 37mm N-37 before the aircraft flew. This was essentially a lighter, less powerful development of the NS-37. Soviet designers estimated that it would take eight 23mm shells, or two 37mm shells, to destroy a B-29. The same armament was retained by the MiG-15, except that the NS-23 was soon replaced by the faster-firing NR-23. In Korea it was shown that this armament, though powerful, was stuck in a fighter that was a poor gun platform and had primitive gunsight. However, the much-improved MiG-17, with the same armament, was very effective in Vietnam.

The supersonic MiG-19 abandoned the N-37. Initial deliveries had two NR-23 cannon, but the standard weapon was the NR-30, basically a scaled-up NR-23. But for its first generation of Mach 2 fighters, the Su-9 and MiG-21, the USSR too abandoned guns. On all-round fighters they soon returned. The twin-barrel GSh-23 guns were installed on the MiG-21 and the MiG-23. This weapon uses the Gast principle, named after its inventor Carl Gast, who developed it in Germany during WWI. In these guns, the firing of one barrel drives the action of the other half of the gun.

Name Ammunition Rate of FireMuzzle velocityWeight Q-factor
GSh-23L 23 x 115 ( 200 g) 3400 rpm 740 m/s 72 kg 43100
Gast guns.

Modern Fighter Guns

The choice for modern fighters is generally between revolver guns and rotary guns. The former are lighter and fire more rounds in a short burst, the latter have a higher sustained rate of fire.

For European aircraft projects, including the Tornado and the Typhoon, the Mauser BK 27 was developed. This 27mm revolver cannon is a new design. No attempt was made to use existing ammunition, and the 27mm calibre is unique. The BK 27 was also adopted for the Swedish JAS 39 Gripen. The BK 27 was also considered for the American F-35, but this plan was abandoned.

The French alos developed a new gun for the Rafale, the GIAT 30/791. This is one of the fastest-firing single-barrel guns, thanks to the use of a seven-chamber cylinder.

Current Soviet fighters are armed with the six-barrel GSh-6-23 and GSh-6-30, or with the single-barrel GSh-30-1. The MiG-31 has the very fast-firing GSh-6-23. This is probably the fastest-firing gun in use, and the manufacturer claims rates of fire as high as 10000 to 12000 rpm for this gun! The GSh-6-30 was used on the MiG-27, for ground support missions. But apparently the GSh-30-1 is preferred for the MiG-29 and Su-27 because of its greater destructive power and lower weight. The GSh-30-1 is unique, because it is the only linear action gun used in a modern fighter. Its rate of fire is similar to that of a revolver cannon, and the GSh-30-1 is considerably lighter. And while its muzzle velocity is modest by modern standards, its accuracy is reported to be very good.

The USAF and USN again show conservatism. Development of the new 25mm GAU-7 gun using caseless ammunition was abandoned, and the old M61 is still the main fighter gun. Some effort has been made to reduce the weight of the gun, which also decreases spin-up time. The disadvantage of the M61 is now the relatively small killing power of its ammunition: Other nations have now adopted larger calibre guns, that fire rounds two or three times heavier than the M50 ammunition of the Vulcan. These 20mm rounds are still the same size as that adopted for the M39s in the 1950s, and at time they were deemed acceptable in the belief that guns would soon become obsolete!

The table below gives the firepower parameters of some modern fighters. Note that the apparent advantage of rotary guns in rate of fire would decrease if short bursts are fired, because of their longer spin-up time. Data for the number of rounds fired in the first second by the M61A1 vary from 47 to 72.

Fighters Guns Rounds/sec Weight/sec
MiG-31 1 x GSh-6-23133.3 26.7 kg/sec
Su-27, MiG-29 1 x GSh-30-130.0 12.0 ks/sec
Rafale C 1 x 30M79141.7 11.5 kg/sec
F-14, F-15, F-16, F-18 1 x M61110.0 11.1 kg/sec
Mirage 2000 2 x DEFA 55430.0 8.3 kg/sec
JA 37 Viggen 1 x KCA22.5 8.1 kg/sec
Eurofighter, JAS 39 Gripen 1 x BK 2728.0 7.4 kg/sec

This can be compared with the data for WWII Fighters. At the end of WWII, the best fighters had an armament firing about 5kg/sec. All modern fighters are well above that, but the difference is smaller than one would expect. The reason is the decreased importance attached to guns in modern air combat, as missiles are now the primary weapon. The is less pressure to improve firepower than there used to be. This is particularly obvious for US fighters: If only the guns are taken into account, the F-22 ended up slightly less firepower than the F-100 Super Sabre!

Next: Korean War Fighters

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s