This war is unique in all history, in that more people have participated personally than in any other armed conflict since time began. The airplane, turned from cargo to weapon bearer, has given members of every race, color and creed, a chance to see, hear, and all-too-frequently to feel the stinging quality of death-dealing implements. Actually, this conflict is more than a decade old. It started when Kawanishi biplanes, armed with two small-caliber machine guns, strafed coolie barges along China's rivers. Italians glorified the use of air weapons against the helpless Ethiopians. Air borne musketry and ordnance got its first full-scale test on the defenseless flesh of Spain.
Until recently, no air, weapon used on any appreciable scale was a pure wartime product. Many of them were born in the last war. Competitive armament was simply a process of digging up existing weapons and adapting them to air use. This made good sense, for man had been fighting on the ground much longer than in the air, and it would have been foolish for air strategists to ignore this accumulated knowledge.
Aside from bombs and rockets, the main armament of aircraft in the bored class (machine guns and cannon), is divided into two general categories. There are air-to-air weapons used between airplanes in a struggle for mastery of the space over an area, and air-to-surface weapons with which the planes can attack troops, armored vehicles, fortified ground positions, rolling stock, or vessels of various kinds. While there is no distinct line drawn between the two classes of weapons, and while air-to-air weapons can be grouped to attack surface objectives, the general trend seems to be toward specialized weapons. Basic job of the air-to-air gun is to kill or disable the crew of the enemy airplane. Failing in this, it must either set it afire or shoot off enough of the airframe or power plant to render the craft unflyable.
Because of the great variety of ground targets, the possible range in size and trajectory of air-to-ground missiles is subject to great variation.
Air-to-air weapons come in two general sizes, the third- and half-inch class. We and the British still use the caliber system of measurement (decimals of an inch) to measure bore widths. The rest of the world uses straight metric measure. Out of the last war, aircraft inherited the rifle-caliber machine gun as its main weapon. In the last days of that conflict, airmen and air strategists conceded that the one-third inch weapons were inadequate and began seeking heavier air weapons. The 37- and 20-mm cannons were produced, but the war ended before their effect could be noted to any large degree.
During the slow, painful period of development following the war, the rifle-caliber air weapon was jammed down the throats of air forces by politically, tactically and financially more powerful ground generals. It should be noted that the one-third inch weapon generally declined in importance as the dominance of ground over air command decreased. The ground commanders wanted the rifle-caliber gun standardized for all the services for reasons of supply, and, for a time, the logistic argument was the first consideration.
In the United States our standard .30-cal Browning gun, frequently interchangeable with the ground weapon, has all but vanished. In the Army, it appears only in training aircraft, where it is used because the ammunition is lighter and cheaper. No Army tactical plane of any consequence carried a .30-cal gun. The Navy still has a few positions armed with .30's, with the Curtiss Seagull and Vought Kingfisher carrying these lighter weapons, despite opposition in some quarters.
Until recently, the RAF's main weapon was the .303 Browning. Conservative British logistics held firmly to this strict standardization. The immortal early Hurricanes and Spitfires tried to make up for the lightness of their fire power by putting four of them in each wing. This made the ship's rate-of-fire 6,600 rounds per minute. However, their maximum effectiveness depended on the fact that the guns were harmonized, or set to fire a close pattern at a set distance. This required a high grade of gunnery, and the amount of weight invested in the guns themselves was out of proportion. The extent to which the British were willing to stick to their original premise is best shown by the battery of 12 of the .303 guns, mounted in some early versions of the Hawker Typhoon.
Russia's .30 is the most remarkable of the class, the light, simple 7.6 mm Shkas. Some modifications can be rigged to fire our M1 and M2 ammunition, but the aircraft variety shoots an electro-sensitive shell at a controlled rate up to 1,800 rounds per minute. Since the days of long-barreled flintlocks, the Circassian gun barrels, reported to be the world's first bored weapons, were famous for their longevity. The Cossack bought a gun for himself, his son and his grandson, and hunting weapons over a century old are still found in the back country in fair shooting shape after constant use. Part of this skill has gone into Red machine gun barrels, which constantly astound experts with their ability to stand up under high-speed fire. Some versions of the I-26 and the I-20 carry six of these in the wing outside the propeller arc, to support a hub firing gun. Their collective rate-of-fire was as high as the Spitfire's.
Germany's main rifle-caliber units measure 7.9 mm in width, the equivalent of .31 cal. The fixed weapons are synchronized so as to fire through the propeller on the Me-109F and the Focke-Wulf 190 to support the heavier guns. Their job, in the fixed installation, is chiefly to "line up" the shots for the wing- or hub-firing cannon. They are used for the same purpose in the new Messerschmitt 210 and 410 fighter bombers. There seems to be a marked outward trend for these guns from a fixed position, some of the later models having recently been spotted carrying heavier machine guns synchronized on the cowl.
Virtually all German medium bombers use flexible 7.9 guns for lateral defense. These are usually the MG-81 series of single or free guns, slid through holes in the side window for taking pot shots at the enemy.
One of the newer gadgets which the Germans are using in order to use up their stockpile of 7.9 guns and ammunition is a streamlined shape about the size of a droppable gas tank, called a waffenbehalter. This contains up to a half-dozen 7.9 guns and ammunition, and is hung in pairs on either side of a Dornier 217 or Ju-88. After the ship has finished its strafing run and must get away, the entire unit is dropped and the ship lightened for escape.
The Italian 7.7 mm Breda-SAFAT gun is so close to the Vickers-Browning that it can shoot the RAF's ammunition without conversion. Recoil and blowback operated, it fires up to 800 rounds per minute and has proved a satisfactory but unspectacular weapon. Most of the standard Italian fighters, the Macchi 200 and 202, carried two of these outside the prop arc on the wings, supporting heavier synchronized guns.
Japan started the war using the 7.7 gun as her standard air gun and heavy ground weapon. The fixed gun was the 97 model, a literal copy of Britain's .303 Vickers gun for fixed mounting. This was used in a synchronized nose mount on Zeke, to support her heavier armament, and was also used to arm the bombers and torpedo planes that bombed Pearl Harbor. These were frequently supplemented by their type 92, an almost exact copy of the World War I Lewis gun, in flexible mounts. The most recent addition to this family was an exact Nambu copy of Germany's Rheinmetall Borsig 81 design. This seemed to arrive around the same time that the first Me-109's arrived to face the Allies in the Burma-India theater. Some of the later modifications of Nell, Betty and other Jap medium bombers have single and double racks of this 7.9 gun in their side or waist positions.
Almost universally, the trend is away from the one-third inch class weapon. Many factors contributed to its fall. First, it was a light weapon and, even in the single-seater class, the gun had to be closely harmonized for maximum effect. In the case of British bombers, where 2 or 4 of them were mounted in power-driven turrets, they had to allow the enemy to get in dangerously close for effective shooting. This restricted the bombers to night operation, or made them operate under heavy escort. Note the fact that when the British discuss using their Lancasters for daylight runs, they also discuss rearming the plane.
The ancestor of the half-inch class gun was the .51-caliber Sharps carbine of the Civil War period. Buffalo Bill made the gun immortal when he used it for hunting bison. The gun was developed by big game experts into the famous elephant gun, the sole weapon that could be used for pachyderms. When the Germans were confronted with the first tanks during World War I, they dusted off the sportsman's rifle and, with some modernization and militarization, used it against tanks. In the post-war search for better air-to-air weapons, the late General Mitchell became interested in the .50-cal ammunition captured from the Germans, and encouraged the Colts Patent Firearms Co, in their experiment with it. To obtain a test weapon, they scaled up the standard .30-cal aircraft gun and without making a major change, they achieved the first truly modern air-to-air gun.
When airmen asked for special guns and ammunition, during the early twenties, economy-minded legislators and a few earth-bound horse commanders almost doomed the .50-cal weapon. Then a few ground technicians discovered that the weapon might be useful as a heavy offensive weapon and the 50-cal project was resumed. Now it is used, fixed and free, on virtually every fighter and bomber we own. The Thunderbolt carries eight, some versions of the Boeing B-17 Flying Fortress tote as many at fifteen, the new super bombers will bristle with them.
England's half-inch class did not fare so well. In the days when the ground forces rescued the United States air gun, arch-conservatives in Britain stymied Vickers 12.7-mm project. The company eventually salvaged its experimental investment by selling it to Breda of Italy. It became Italy's standard heavy gun, and it appears on as the fixed synchronized gun on the Fiat Falcho, the Macchi Saetta and 202, the Reggiane Re 2001 and other craft. Virtually all turrets on Italian bombers carry this 12.7 gun.
When Germany discovered that the .50-cal gun was the most effective air-to-air weapon in existence, the Italian gun was redesigned for German use, emerging as the MG-131 13-mm heavy machine gun. This is used in many of the single-place fighters in place of the synchronized 7.9 guns, also appears in the Junkers Ju-88 and the Dornier Do 217 in power-driven dorsal turrets and in ventral handmounts. Its most spectacular application is in the side-barbettes of the Messerschmitt 210 and 410.
Japan's 12.7 Tasuku gun is rapidly replacing the lighter 7.7 weapons because of our universal use of the .50-cal Zeke, Hap, Oscar, and the new Tony, all carry 12.7s as main or auxiliary armament, and the newest type Betty and Helen bombers carry 12.7s in manual turrets on top.
Russia's half-inch gun is the UB model with a 12.7 bore. The Shkas scaled up to size, it is ranked as the crown prince of the 50s. Electrically fired, it shoots over 1,000 rounds per minute. The main weapon on the new La-5 radial air-cooled fighter, its rate-of-fire permits the use of fewer guns. The first La-5s carried two 12.7s and two 7.6s. The latest information indicates that both the wing guns and synchronized guns are now half-inch weapons.
Our .50-cal gun, used in multiples of six to eight, in such vehicles as the B-25 Mitchell or the A-20 Havoc, is useful in attacks against parked airplanes, or on fields heavily defended by flak. For all practical purposes, any air-borne gun over the half-inch class is rated as a cannon. The only possible exception is Germany's 15-mm hub-firing cannon used in some of the Messerschmitt 109Fs.
The next class up is the 20-mm size. With one exception, all 20-mm guns have one ancestor, the 20-mm Becker gun, designed by an Austrian in 1918. A few of them were built, but none saw action at that time. In 1919, the inventor, seeing no possibility for his weapon in Germany, sold the rights to Oerlikon in Switzerland.
Japan's 20-mm cannon is a straight Oerlikon copy. A short-barreled version is used in her fighters, Zeke, Hap and Rufe, and in flexible mounts in the tail of the heavy twin-engined bomber, Betty, and the four-engined flying boat, Mavis. The Jap 20-mm cannons have been only moderately successful and the Japs evidently hope to do better with multiple 50-cal guns.
Most weapons above 20-mm are virtually useless as plane-to-plane guns. Their rate-of-fire is so slow that the chance of getting a hit on the enemy plane is virtually nil. The ancestor air-to-air gun is the 37-mm cannon which Hispano-Suiza fitted into the engine-hub of Guynemer's Spad in the late days of World War I.
The sound in the wind seems to indicate heavier guns being sky borne. The newer uses to which planes are being put for ground-army cooperation calls for more gunpower. No one knows what tomorrow's weapons will be, but one shouldn't be surprised at 155s and bigger bearing wings before combat is over.
This article was originally published in the March, 1944, issue of Air News magazine, vol 6, no 2, pp 28-30, 69.
Air News was published on newsprint in 10½" × 13½" format.
The original article includes 28 photos of aircraft gun installations and the planes that carry them, and one line drawing of Madsen MG and cannon in the nose of a twin-engined fighter.
page with 13 photos , page with 15 photos.
A PDF (14 MiB) of the article, which includes the illustrations, is available.
Photos credited to Acme, Rudy Arnold, International, Boeing, Schostal Press, Lockheed, British Information, Air News, Sovfoto, Black Star, British Combine; drawing credited to Flight.