An automatic weapon is a gun, rifle, or pistol that fires continuously without any external aid such as hand-cranking (or even electric power) for as long as the trigger is pressed. Early designs were hand-cranked in one way or another, but they laid the framework for the first true automatic designs.

 

Early American designs

The best known early mechanical weapon was the Gatling (Figure 1), developed by the American inventor Richard Gatling (1818–1903) and first demonstrated in 1863. This used six barrels rotated by a hand crank and for 50 years the design was sold and copied throughout the world using a wide variety of calibers (barrel sizes). Later true automatic weapons used electric motors or gas pressure taken from the barrel. In the blowback action, part of the explosive force propelling the bullet ejects the spent cartridge and re-cocks the firing mechanism. In a gas-operated weapon hot gases led from the barrel force back a piston that works the ejection and re-cocking mechanisms.

 

Another American design was the Lowell gun, produced in 1875. This was also a hand-cranked weapon but one that overcame the heating problem affecting all machine guns after 300 or 400 rounds (bullets) have been fired, when the barrel becomes too hot for further use. It had four barrels, one of which was used at a time. When this became too hot a new barrel was rotated into position.

 

The next development came from another American, Hiram Maxim (1840–1916). He designed an automatic weapon (Figure 2) in London, starting by modifying a Winchester rifle. He used a hook fixed to the barrel to lock the bolt in place for firing. The recoil drove both hook and bolt back until the hook was lifted by passing under a bridge. The bolt continued back, driving round a crank to extract and reload the cartridge and was then forced back by a spring. Ammunition was fed into the gun by means of a belt, which could be joined to successive belts to provide continuous feed for long periods of firing.

 

Satisfied with the success of this design, Maxim simplified it and set up a company to produce the gun with Vickers, the shipbuilding company. Demonstrations in Europe impressed everybody who saw the gun in action. Vickers eventually took over the company and developed an improved version of the Maxim, which became the standard machine gun for many years.

 

As designs proliferated three main mechanisms came into use: blowback, recoil (as in the Maxim) and gas-operation. With the recoil method, the breech is locked to the barrel and they move back as one to start the cycle of extraction, ejection, cocking, feeding, chambering, locking and firing again.

 

World War II

By the start of World War II machine guns were grouped into three main types: the light machine gun such as the Bren (Figure 5), which can quickly be set up and fired; the medium machine gun such as the Vickers, capable of sustained fire but of necessity heavier and more robust; and the heavy machine gun used against aircraft and similar targets. The differences between the types are, however, more tactical than technical. The light or sub-machine gun was not popular until it proved its worth in the war in the shape of the many excellent German weapons such as the Erma, numerous cheap and simple Russian weapons and the Sten and Thompson (Figure 4).

 

The Americans relied on massed fire-power from the Garand or M1 automatic rifle, described by General Patton (1885–1945) as "the best battle implement ever designed". This was a gas-operated rifle of great simplicity and reliability. It was augmented later by a shorter carbine for use by troops (other than front-line infantry), who found a full-size rifle a hindrance. This was the concept behind the Belgian FN automatic rifle (Figure 6) after the war.

 

Automatic pistols and later developments

"Automatic" pistols (strictly speaking, semi-automatic weapons) started to come into their own at the turn of the century (Figure 7). One of the best known – the 9-millimeter Luger —went into service in 1908. It was officially replaced by the Walther P38 in 1938, but remained in general use although, being a particularly well-made gun, it was dependent on the quality of the ammunition. The advantages of the automatic over the revolver was its more rapid rate of fire and larger magazine. But it was more likely than the simpler revolver to jam in dirty conditions. This is one of the crucial points in the designs of all weapons, particularly automatics. These guns have to be able to operate in extreme conditions without loss of efficiency.

 

With the coming of fighter planes, then bombers that needed to defend themselves, the machine gun took to the air. The Lewis gun, Spandau and Hotchkiss were used in World War I fighters, with eight 12.7-millimeter (0.5-inch) guns being mounted in fighters in the later stages of World War II, and up to 13 in the Flying Fortress bomber. Brownings were the most popular choice of Allied forces.

 

With the coming of fast fighters the target was often in range for only a split second and was generally heavier and stronger. Cannon (with explosive bullets) began to replace machine guns long before the war ended but the ultimate weapon for this purpose came with the development of the rotating-barrel Vulcan, which uses a similar principle to the Gatling for its phenomenal rate of fire.

 

The GEC Vulcan was designed for use in fighters in its 20-millimeter form. Later the 7.62-millimeter MiniGun was developed for helicopter use in Vietnam against ground targets, where the 6,000 rpm rate had devastating results. The Vulcan is here mounted on a tracked chassis for anti-aircraft work with a power-operated traverse to track low-flying supersonic aircraft. Although wasteful of ammunition, the Vulcan represents the optimum in current machine guns.