Rotary cannon

A rotary cannon is a large-caliber, multiple-barreled automatic firearm. It uses a Gatling-type rotating barrel assembly to deliver sustained, direct fire. This design allows for a much higher rate of fire than single-barreled autocannons of the same caliber. Because these weapons are often heavy and cumbersome, they are typically mounted on large platforms. These platforms include vehicles, ships, and aircraft. They are frequently used as close-in weapon systems to protect these larger assets.

The mechanism of a rotary cannon relies on a synchronized, repeating cycle. As the entire barrel assembly rotates, different functions occur in different barrels at the same time. First, a barrel reaches a specific position to fire a single cartridge. Next, the assembly continues to turn so that a different barrel ejects the spent casing. Finally, a third barrel loads a new round into place at another position in the rotation. This simultaneous operation allows the gun to fire much faster than a single-barrel design.

This rotating design also solves two major engineering problems: heat and malfunctions. In a single-barrel weapon, continuous fire causes rapid barrel heating. This often leads to stoppages caused by overheating. In a multi-barrel rotary gun, the barrels have more time to dissipate heat into the surrounding air between shots. For example, a five-barreled gun firing at 1,000 rounds per minute only fires 200 rounds per barrel per minute. Additionally, rotary cannons are resistant to defective ammunition. Since the power source is usually external, the gun can simply extract a defective round like a regular spent casing.

The history of these weapons began in the mid-19th century. In 1852, an Irish immigrant named Delany proposed a revolving barrel gun with a unique ignition method. Later, Dr. Richard J. Gatling designed the famous Gatling gun in 1861. He patented the design in 1862. This early version was hand-cranked and used a hopper to feed ammunition. It initially fired 200 rounds per minute. By 1876, the design had a theoretical rate of 1,200 rounds per minute. However, the weapon was quite heavy and difficult to move over rough ground. The U.S. Army eventually declared all Gatling guns obsolete in 1911.

Modern development was driven by the need to hit fast-moving jet aircraft after World War II. The U.S. Air Force required large-caliber shells that could carry more explosives. In 1946, the General Electric Company began Project Vulcan to develop such a gun. Engineers even tested a 40-year-old museum Gatling gun with an electric motor. This test reached a rate of 5,000 rounds per minute. In 1956, the T171 20mm gun was standardized as the M61 20mm Vulcan. This became a famous aircraft gun used by the U.S. Army and Air Force.

There are several types of rotary cannons used today. The M61 Vulcan is a six-barreled 20mm autocannon that fires up to 6,600 rounds per minute. Another famous example is the GAU-8 Avenger. This is a seven-barreled 30mm autocannon used on the A-10 Thunderbolt II aircraft. It is the heaviest autocannon ever mounted in an aircraft. It outweighs the German WWII Bordkanone BK 7,5 by about 630 kg when including ammunition.

Other nations use different designs, such as the Russian GSh-6-23 and GSh-6-30. These are gas-powered cannons that can reach rates of 9,000 to 10,000 rounds per minute.

Powering the rotation is another way these guns differ. Most modern Gatling-type guns are externally powered by electric motors. However, some are self-driven using gas or recoil. The Russian GShG-7.62 and GSh-6-23 use a gas piston drive in the center of the barrel cluster.

During the Vietnam War, the M134 Minigun was used on helicopters. It could fire between 2,000 and 6,000 rounds per minute. This weapon was also used on AC-47 gunships, which were nicknamed "Puff the Magic Dragon." These diverse systems show how rotating technology can be adapted for many different roles.