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In 1885 the American inventor, Hiram Maxim, demonstrated the world's first automatic portable machine-gun to the British Army. Maxim used the energy of each bullet's recoil force to eject the spent cartridge and insert the next bullet. The Maxim Machine-Gun would therefore fire until the entire belt of bullets was used up. Trials showed that the machine-gun could fire 500 rounds per minute and therefore had the firepower of about 100 rifles.

The Maxim Machine-gun was adopted by the British Army in 1889. The following year the Austrian, German, Italian, Swiss and Russian armies also purchased Maxim's gun. The gun was first used by Britain`s colonial forces in the Matabele war in 1893-94. In one engagement, fifty soldiers fought off 5,000 Matabele warriors with just four Maxim guns.

The success of the Maxim Machine-gun inspired other inventors. The German Army's Maschinengewehr was based on Maxim's invention. John Moses Browning produced his first machine-gun in 1890 and five years it was adopted by the US Navy.

By the outbreak of the First World War, the British Army had adopted the Vickers Machine-gun Fitted with interrupter gear, the Vickers was also standard armament on all British and French aircraft after 1916. During the war the British also used the Lewis Gun. Easier to produce and far lighter than the Vickers, it was used by soldiers on the Western Front and on armoured cars and aircraft.

In the Second World War the British Army used the extremely reliable Vickers 303. It was a recoil-operated machine gun, water cooled and belt fed. It weighed 40lb without its tripod and fired the standard .303 British cartridge at about 450rpm.

During the war the German Army developed the MG42 machine-gun. Its 1,000rpm could be extremely wasteful during battle. The Red Army used the Maxim-Gun at the beginning of the war but later switched to the drum-fed and gas-operated Degtyarev Model 1940. The United States Army preferred the Browning M2 that fired 100 round belts at 450 rpm.

History of U.S. Military Machine Guns: Part 3

A U.S. soldier in Vietnam carrying an M60 machine gun. CREDIT: YouTube

By the end of World War II, engineers largely had the concept of the machine gun figured out. Air-cooled designs now functioned well at high rates of fire, and strategies for effectively using suppressing fire had been developed and battle tested. As with the progression of any technology, guns got smaller and lighter as time went on. At this point in machine gun history, nearly all the firearms used by the U.S. were largely just improved versions of earlier actions, usually those created by the late John Moses Browning.M60 General Purpose Machine Gun (1957)

After World War II, there was a push for a new, lighter machine gun that could be more easily used at the infantry level, and still serve multiple roles as a fixed-position gun. To that end, development of the M60 machine gun started in the late 40s. The design capitalized on captured German technology from the FG 42 and MG 42, as well incorporating influences from the failed M1941 Johnson LMG.

The FG42 was basically an improved Lewis Gun, with the Germans building upon the effective design by the American inventor. American engineers would borrow from that, copying the overall layout, bolt, and gas piston system. The MG 42 struck fear into the hearts of American G.I.s with its exceptional rate of fire, earning the nickname Hitler’s Buzz Saw, because of its distinctive sound. The belt feed components and top cover were appropriated from this design for the M60.

The experimental T-44 prototype developed from the German FG 42 and MG 42 machine guns. Wikimedia Commons

Early prototypes, such as the T52 and T161, looked like a child born from marriage of the M1941 Johnson LMG and the FG 42. The sum of these parts was a gas-operated, air-cooled, belt-fed machine gun capable of full-auto fire only. Of particular note is the unique gas system, which used the “gas expansion and cutoff” principle also found in the M14.

This system was simpler than many of its contemporaries, and was particularly easy to clean. The resultant gun was known as the T161E3, which was changed to M60 when the U.S. Army officially adopted it in 1957. The new weapon fired 7.62x51mm NATO from an open-bolt at a rate of 550 rounds per minute.

A U.S. Marine fires his M60 machine gun at an enemy position during the Battle of Huế in Vietnam War. Wikimedia Commons

The M60 would become the face of Vietnam conflict, finding its way into the bush and skies alike, with all branches of service. It served as the door gun in the infamous Huey helicopter that both put many in harms way as well as ushering them to safety.

The gun was nicknamed “The Pig,” by grunts in the field, though the origins of that nickname are a bit muddy. Some say the gun earned the moniker because of its 24-pound weight, while others contend that the sound it made resembled that of a hog.

One thing is certain, every member of a squad would carry 200 rounds of belted ammo to feed The Pig, with some carrying spare barrels as well.

The original M60 was designed to be a crew-served machine gun, with one man shooting, and another feeding the ammo belt. Later variants made the system much easier to operate by one person.

The gun used 7.62 NATO ammunition in a disintegrating belt held together by M13 links, which replaced the M1 links used with the M1917 and M1919 Browning machine guns in the mid 20th century.

An M60 machine gun team changes barrels using an asbestos mitt. Wikimedia Commons

Anyone that is an Alice in Chains fan likely knows the story about guitarist and lyricist Jerry Cantrell’s father, as told in the song Rooster. The gun the protagonist used was likely an M60D, a pintle-mounted variant of the M60 that saw service as the door gun in most of the choppers that visited sunny Southeast Asia during the Vietnam War.

It replaced the short-lived M60B, which was held by the gunner—obviously not a good solution. Unlike other models in the M60 line up, the D has spade grips. It also features a ring-type sight more typically found on aircraft guns.

In Full Metal Jacket (1987), the door gunner (Tim Colceri) uses a pintle-mounted M60.

To prevent helicopter engines from ingesting spent casings from the gun, which could cause a real problem, the M60D was fitted with a canvas brass catcher to intercept ejected casings and links before they caused an issue. The gun is most associated with the UH-1B Huey, but it also found its way onto the CH-47 Chinook, the ACH-47A, and on the UH-60 Black Hawk.

The M60D has been mostly replaced by the M240H on U.S. aircraft, but U.S. Ordnance-built M60Ds are still used on the SH-60 Seahawk.

Despite drawing on a number of successful firearms and serving through the Vietnam War and into the 1980s, the gun was not without its flaws. The fire control mechanism was known to fall out if jarred hard enough to defeat the single spring locking it in place. There were stories of M60 gunners reaching down to find their pistol grip and trigger missing, dropped somewhere a few miles back in the dense brush.

The gas system was held in place with a single nut, which could walk off with recoil and the heat of long strings of fire. This was remedied in the field by wiring the nut in place, which significantly slowed barrel changes.

The lack of a carrying handle also created issues when it came time to switching barrels. The Army issued an asbestos mitt to grab hot barrels, much like it did for the M1919 in WWII. But getting this glove on in the midst of a firefight was less than ideal.

Additionally, the way the action was designed required a metal part attached to the barrel to actually impact the bolt face during firing, sending it backward. This caused peening, which was remedied by regular filing to keep the guns running and often required replacement of the bolt after enough use.

The metal in the receivers was made relatively thin to save on weight. While many served well through Vietnam, later in life, when they’d had a few thousand rounds through them, they began to fail and spread apart. This was a particular problem in the 1980s when a lot of M60s were nearing the end of their lifespan.

A Marine “Huey” helicopter covers Marines on patrol with an M60 in Born on the Fourth of July (1989).

The Army went back to the drawing board in an effort to rectify these issues. The first attempt was designated the M60E3. The first issue they sought to address was the gun’s weight, shaving ounces wherever they could to drop from 23 to about 18.5 pounds.

These reductions in weight also included making the barrel thinner, which required the cyclic rate to be turned down to 200 rpm.

Some claimed that the Stellite Superalloy barrel liner that was added made long strings possible, but the excessive heat generated usually shut down operation of the gun. To deal with this, two barrels were created, a lighter variant for infantry use and a heavier one more suited to prolonged suppressive fire from a fixed position.

A few features were added on the M60E3 to make the gun more useful in the field. It included a bipod attached to the forearm, which didn’t complicate barrel changes, and greatly improved stability. A vertical forward grip was also included, allowing the operator to fire from a standing position and from the shoulder. An ambidextrous safety was welcomed by gunners, as was the universal sling attachment points that meant the gun didn’t always have to be carried over one’s shoulder.

A carrying handle was added to the barrel, which facilitated swapping hot barrels without gloves. The gas system was simplified in an effort to speed cleaning. The reduced-weight parts found life on the battlefield difficult as a result, durability suffered. The gun unfortunately now experienced more breakages and accelerated wear than its predecessors.

The M60E3 was a lightweight version of the machine gun developed in the mid 1980s for the U.S. Marine Corps and adopted in 1986 to replace their stocks of original production M60s, which were starting to wear out after extended use. The decreased weight led to decreased reliability and heating problems.

The next evolution is the M60E4, built to eliminate the problems that were created during the last round of tinkering. Externally, the gun stayed much the same, but was given a different forward grip, iron sights, butt stock and bipod. Most of the changes occurred on the internal components, with a goal of enhanced reliability.

The feeding system was given a facelift, fitted with a new pawl that pulled the belt with greater force. Early models had a duckbill flash suppressor, though these were ultimately phased out.

A mounted M60E4 crewed by a Seabee on a convoy in Iraq, May 2003. Wikimedia Commons

The gun gained a few pounds, but still remains lightweight at about 20.5 lbs. The footprint was also shrunk a bit to make it easier to maneuver in the tight spaces often encountered in jungle and urban warfare. As a result, the automatic weapon can be shoulder-fired with a fair degree of accuracy. The M60E4 now has multiple M1913 Picatinny rails for mounting optics, lasers, night vision systems and other accessories.

The gun can be used on all NATO Standard mounts, though some do require an adaptor. All of the major components interchange with the legacy M60s, with U.S. Ordnance manufacturing a conversion kit to upgrade older models. Despite these advances, the M60 was largely phased out in the U.S. military by the adoption of the M249 SAW.

6 Important Machine Guns from World War One

As the first truly modern war, the First World War exposed antiquated fighting techniques to modern technologies. Perhaps the most iconic of these is the machine gun.

It gave the defending force an overwhelming advantage, and significantly reduced the mobility of the war. It meant that many lives had to be sacrificed for small gains to made.

Below is listed six of the more important models.

Machine Guns

Machine guns inflicted appalling casualties on both war fronts in World War One. Men who went over-the-top in trenches stood little chance when the enemy opened up with their machine guns. Machine guns were one of the main killers in the war and accounted for many thousands of deaths.

Crude machine guns had first been used in the American Civil War (1861 to 1865). However, tactics from this war to 1914 had not changed to fit in with this new weapon. Machine guns could shoot hundreds of rounds of ammunition a minute and the standard military tactic of World War One was the infantry charge. Casualties were huge. Many soldiers barely got out of their trench before they were cut down.

A British Vickers machine gun crew at the Somme

This British Vickers machine gun is being fired by a team of two who are wearing early gas masks in case of a gas attack. To ensure that the machine gun’s barrel did not overheat, the weapon was cooled using a large water cooling jacket. An ammunition belt fed it bullets. This machine gun could shoot 450 rounds a minute. As well as the Vickers machine gun, the British used the Hotchkiss and the Lewis gun.

At the start of the war, senior British army officers were less than sure about the effectiveness of the machine gun. Therefore most battalions were only issued with two.

This was a lot less than the Germans who were much more sure as to the effectiveness of the machine gun. The Germans placed their machine guns slightly in front of their lines to ensure than the machine gun crews were given a full view of the battlefield. At the Battle of the Somme, their efficiency lead to the deaths of thousands of British troops within minutes of the battle starting.

Going over the top at the Somme

This still above was taken from film as British troops ‘went over the top’ at the start of the Battle of the Somme. Within a few strides from their own trench, these men were almost certainly the victim of German machine gun fire.

From Machine-guns to Cannons

The first attempt to install cannons firing explosive shells had been made during WWI. The British found that the recoil caused their planes to stall. The French were more successful, equipping some of their aces with 37mm cannon.

By the start of WWII, machine-guns were still standard. However, improved plane armor and the self-sealing fuel tank enabled planes to survive hits they could not have done before. Explosive rounds were needed to take them down.

There was a balancing act in deciding what weapons to equip planes with. The German Messerschmitt Bf109 could fire five shells a second from its cannon, allowing quick hits with explosive rounds. The British Hurricane’s eight machine-guns could spray 160 bullets in the same amount of time. The choice was between quantity or quality.

The result was often a compromise. The British installed later models of their Hurricanes and Spitfires with a mixture of cannons and machine-guns.

Groundcrew of No. 274 Squadron RAF overhaul Hawker Hurricane Mark I (V7780 “Alma Baker Malaya”) at LG 10/Gerawala, Libya, during the defence of Tobruk.


Combat experience in the Manchurian Incident of 1931 and subsequent actions in Manchuria and northern China reaffirmed to the Japanese army the utility of machine guns in providing covering fire for advancing infantry. [4] The earlier Type 11 light machine gun was a lightweight machine gun, which could be easily transportable by an infantry squad into combat. However, the open hopper design of the Type 11 allowed dust and grit to enter into the gun, which was liable to jam in muddy or dirty conditions due to issues with poor dimensional tolerances. [5]

This gave the weapon a bad reputation with Japanese troops, and led to calls for its redesign. [6] The Army's Kokura Arsenal tested the Czech ZB vz. 26 machine gun, samples of which had been captured from the National Revolutionary Army of the Republic of China, and (after borrowing certain elements) issued a new design, designated the Type 96 light machine gun, in 1936. The gun was produced at Kokura, Nagoya Arsenal and Mukden between 1936 and 1943, with a total production run of about 41,000. [7]

While the Japanese design was completely different internally, it did resemble the ZB vz. 26 in its basic layout using the top feed magazine and a bipod mount. The similar looking Type 97 heavy tank machine gun however was a true license built copy of the ZB design firing the heavier 7.7x58mm Arisaka cartridge it was mounted in the tanks of the Japanese Army.

The Type 96 light machine gun was almost identical in construction to the Type 11 in that it was an air-cooled, gas-operated design based on the French Hotchkiss M1909 machine gun. As with the Type 11, it continued to use the same 6.5x50mm Arisaka cartridges as the Type 38 rifle infantry rifle, [8] although the more powerful 7.7x58mm Arisaka round had already been adopted and was starting to enter into service with front line combat units. Due to its visual resemblance to the British Bren light machine gun they are often mistakenly regarded as clones. [9]

The major difference from the Type 11 was the top-mounted curved detachable box magazine holding 30 rounds, which somewhat increased reliability and lessened the weight of the gun. The finned gun barrel could also be rapidly changed to avoid overheating. The Type 96 had a blade front sight and a leaf rear sight, with graduations from 200 to 1,500 meters, with windage adjustment. A 2.5X telescopic sight with a 10 degree field of view could be attached at the right side of the gun. [8]

The Type 96 also had a folding bipod attached to the gas block, and could be fitted with the standard infantry bayonet, which could be attached to the gas block below the barrel, making it, alongside the later Type 99 the only machine gun used in the Second World War that a bayonet could be attached to. The gun had no select-fire capability. [10]

Despite the fact it could cause stoppages, designer Kijiro Nambu did nothing to address the dimensional tolerance issue between the bolt and barrel, which would lead to feed failure if casings got stuck in the chamber. In order to ensure reliable feeding (theoretically), Nambu resorted to oiling the cartridges via an oil pump in the magazine loader. [5] In practice, this tended to worsen the problem instead, as the oiled cartridges tended to become coated with dust and sand. [11] This feature and its inherent faults were dropped with the introduction of the Type 99 light machine gun.

The Type 96 came into active service in 1936 and was intended to replace the older Type 11 however the Type 11 had already been produced in large quantities, and both weapons remained in service until the end of the war. The Type 96 was regarded as rugged and reliable, but its 6.5 mm bullets lacked penetration against cover, especially in comparison to other rifle rounds of the day such as the American .30-06 Springfield and the design was supplanted by the more powerful Type 99 light machine gun with the larger 7.7 mm bullet in 1937.

After World War II, it was used by Indonesian forces during the Indonesian National Revolution against Dutch forces [12] notably during the attack on Jogjakarta 1949. [ citation needed ] It was used by the Viet Minh and the North Vietnamese forces during the First and Second Indochina Wars. [13]

Gatling Gun

A hand-driven machine gun, the Gatling gun was the first firearm to solve the problems of loading, reliability, and the firing of sustained bursts. It was invented by Richard J. Gatling during the American Civil War, and later used in the Spanish-American War, but was supplanted by advanced weaponry soon after. Years later, the technology behind the gun was re-introduced by the U.S. military, and new versions of the gun are still in use today.

The Gatling gun is a machine gun that consists of multiple barrels revolving around a central axis and is capable of being fired at a rapid rate. Gen. Benjamin F. Butler of the Union army first used the gun at the siege of Petersburg, Virginia, in 1864-1865.

Did you know? Richard Gatling had actually hoped that the tremendous power of his new weapon would discourage large scale battles and show the folly of war.

The gun is named for its inventor, Richard Jordan Gatling, a physician. Gatling neatly divided his sympathies during the Civil War. While trying to sell machine guns to the Union, he was an active member of the Order of American Knights, a secret group of Confederate sympathizers and saboteurs.

The conservatism of the Union army chief of ordinance and the unreliability of early models of the gun frustrated efforts to sell it to the U.S. Army. But Gatling soon improved on the original six-barrel, .58 caliber version of the gun, which fired 350 rounds a minute, by designing a ten-barrel, .30 caliber model, which fired 400 rounds a minute. The U.S. Army adopted the Gatling gun in 1866, and it remained standard until it was replaced in the early twentieth century by the Maxim single-barrel machine gun.

The Gatling gun played an important role after the Civil War, giving small numbers of U.S. troops enormous advantages in firepower over the western Indians. In newly colonized portions of Africa and Asia, the Gatling gun provided the Europeans’ margin of victory over local forces.

A modern, helicopter-mounted version of the Gatling gun, the Vulcan minigun, was widely used by the U.S. Army in the Indochina war. The minigun, popularly known as ‘Puff, the Magic Dragon’ for the flames and smoke emitted from its muzzle, fires at the staggering rate of 6,000 rounds per minute, enough to decimate an entire village in one burst. The minigun continues to be used as a counterinsurgency weapon in Central America. A larger version, the 20mm Vulcan is used for antiaircraft defense.

The Reader’s Companion to American History. Eric Foner and John A. Garraty, Editors. Copyright © 1991 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

The First Machine Gun

The grandfather of the machine gun is the Gatling Gun. Richard Gatling developed this firearm with the idea of saving lives on the battlefield after watching the slaughter that was the American Civil War. The idea being that needing fewer men on the battlefield would result in fewer casualties. Unfortunately, his theory didn’t pan out as he planned.

The Gatling gun and later machine guns didn’t immediately change battlefield tactics, and it wasn’t until the end of the first World War that military leaders realized that marching men in lines against weapons with high rates of fire was suicidal. His invention spawned all future machine guns, which have heavily influenced battlefield tactics and changed the way countries, armies, and squads fight wars.

Model 1883 Gatling Gun

The first machine gun was a multi-barrel (6-10 barrels depending on the model) crank-fired weapon that needed its own squad to operate and maintain the weapon. Each barrel had a bolt and firing pin which meant constant supervision.

The Gatling gun was originally purchased privately by Union military commanders and first saw combat in the Siege of Petersburg in 1864 with devastating effects. A nine-month siege that saw trenches heavily used by both sides. It foreshadowed tactics that would be adopted in the first World War. The Gatling gun was formally purchased by Union forces in 1866. It saw action in several conflicts but due to its weight being comparable to the artillery of the day, it was quickly phased out by machine guns in the early 20th century that were lighter weight, gas-operated weapons, with even higher rates of fire.

How Machine Guns Work

Historians count the machine gun among the most important technologies of the past 100 years. As much as any other factor, it set the brutal, unrelenting tone of World War I and World War II, as well as most of the wars since that time. Unlike earlier guns, which had to be manually loaded and fired, with this machine, one soldier could fire hundreds of bullets every minute, mowing down an entire platoon with only a few passes. The gun would continue to fire until the operator stopped pressing the trigger or the gun finally ran out of ammunition.

Military forces had to develop heavy battle equipment like tanks just to withstand this sort of barrage. This single weapon had a profound effect on the way we wage war. The machine gun gave small numbers of troops the fighting capabilities of large battalions. It also increased the potential for mass casualties.

In light of their monumental role in history, it's somewhat surprising how simple machine guns really are. These weapons are remarkable feats of precision engineering, but they work on some very basic concepts. In this article, we'll look at the standard mechanisms machine guns use to spit out bullets at such a furious rate.

Ballistic Background: Barrel

To understand how machine guns work, it helps to know something about firearms in general. Almost any gun is based on one simple concept: You apply explosive pressure behind a projectile to launch it down a barrel. The earliest, and simplest, application of this idea is the cannon.

A cannon is just a metal tube with a closed end and an open end. The closed end has a small fuse hole. To load the cannon, you pour in gunpowder -- a mixture of charcoal, sulfur and potassium nitrate -- and then drop in a cannonball. The gunpowder and cannonball sit in the breech, or rear part of the bore, which is the open end of the cannon. To prepare the gun for a shot, you run a fuse (a length of flammable material) through the hole, so it reaches down to the gunpowder. To fire the cannon, all you have to do is light the fuse. The flame travels along the fuse and finally reaches the gunpowder.

Gunpowder burns rapidly when it ignites, producing a lot of hot gas in the process. The hot gas applies much greater pressure on the powder side of the¬ cannonball than the air in the atmosphere applies on the other side. This propels the cannonball out of the gun at high speed.

For more on the earliest applications of this technology, read on to the next page.

The first handheld guns were essentially miniature cannons you loaded some gunpowder and a steel ball, then lit a fuse. Eventually, this technology gave way to trigger-activated weapons, such as the flintlock and percussion cap guns.

Flintlock guns ignited gunpowder by producing a tiny spark, while percussion caps used mercuric fulminate, an explosive compound you could ignite with a sharp blow. To load a percussion cap gun, you pour gunpowder into the breech, stuff the projectile in on top of it, and place a mercuric fulminate cap on top of a small nipple. To fire the gun, you cock the hammer all the way back and pull the gun's trigger. The trigger releases the hammer, which swings forward onto the explosive cap. The cap ignites, shooting a small flame down a tube to the gunpowder. The gunpowder then explodes, launching the projectile out of the barrel. (Take a look at How Flintlock Guns Work for more information on these weapons.)

The next major innovation in the history of firearms was the bullet cartridge. Simply put, cartridges are a combination of a projectile (the bullet), a propellant (gunpowder, for example) and a primer (the explosive cap), all contained in one metal package. Cartridges form the basis for most modern firearms. The backward motion of the gun's bolt also activates its ejection system, which removes the spent shell from the extractor and drives it out of an ejection port. We'll discuss this in more detail later. But first, let's take a look at how all of this works -- in a revolver.

Click on the trigger to see how a revolver fires.

In the last section, we saw that a cartridge consists of a primer, a propellant and a projectile, all in one metal package. This simple device is the foundation of most modern firearms. To see how this works, let's look at a standard double-action revolver.

This gun has a revolving cylinder, with six breeches for six cartridges. When you pull the trigger on a revolver, several things happen:

  • Initially, the trigger lever pushes the hammer backward. As it moves backward, the hammer compresses a metal spring in the gun stock (the handle). At the same time, the trigger rotates the cylinder so the next breech chamber is positioned in front of the gun barrel.
  • When you pull the trigger all the way back, the lever releases the hammer.
  • The compressed spring drives the hammer forward.
  • The hammer slams into the primer at the back of the cartridge, igniting the primer.
  • The primer sets off the propellant.
  • The exploding propellant drives the bullet out of the gun at high speed.
  • The inside of the barrel has a spiral groove cut into it, which helps spin the bullet as it exits the gun. This gives the bullet better stability as it flies through the air and increases its accuracy.

When the propellant explodes, the cartridge case expands. The case temporarily seals the breech, so all the expanding gas pushes forward rather than backward.

Obviously, this sort of gun is easier to use than a flintlock or a percussion cap weapon. You can load six shots at a time and you only have to pull the trigger to fire. But you're still fairly limited: You have to pull the trigger for every shot, and you need to reload after six shots (although some modern revolvers can hold 10 rounds of ammunition). You also have to eject the empty shells from the cylinders manually.

Now let's take a look at how gun manufacturers addressed the disadvantages of using revolvers.

Machine Guns and Gun Systems

In the 1800s, gun manufacturers designed a number of mechanisms to address the problems associated with limited firing ability. A lot of these early machine guns combined several barrels and firing hammers into a single unit. Among the most popular designs was the Gatling gun, named after its inventor Richard Jordan Gatling.

This weapon -- the first machine gun to gain widespread popularity -- consists of six to 10 gun barrels positioned in a cylinder. Each barrel has its own breech and firing pin system. To operate the gun, you turn a crank, which revolves the barrels inside the cylinder. Each barrel passes under an ammunition hopper, or carousel magazine, as it reaches the top of the cylinder. A new cartridge falls into the breech and the barrel is loaded.

Each firing pin has a small cam head that catches hold of a slanted groove in the gun's body. As each barrel revolves around the cylinder, the groove pulls the pin backward, pushing in on a tight spring. Just after a new cartridge is loaded into the breech, the firing-pin cam slides out of the groove and the spring propels it forward. The pin hits the cartridge, firing the bullet down the barrel. When each barrel revolves around to the bottom of the cylinder, the spent cartridge shell falls out of an ejection port.

The Gatling gun played an important role in several 19th century battles, but it wasn't until the early 20th century that the machine gun really established itself as a weapon to be reckoned with.

The Gatling gun is often considered a machine gun because it shoots a large number of bullets in a short amount of time. But unlike modern machine guns, it isn't fully automatic: You have to keep cranking if you want to keep shooting. The first fully automatic machine gun is actually credited to an American named Hiram Maxim. Maxim's remarkable gun could shoot more than 500 rounds per minute, giving it the firepower of about 100 rifles.

The basic idea behind Maxim's gun, as well as the hundreds of machine gun designs that followed, was to use the power of the cartridge explosion to reload and re-cock the gun after each shot. There are three basic mechanisms for harnessing this power:

In the next couple of sections, we'll discuss each of these systems.

Machine Gun Recoil Systems

Click and hold the trigger to see how a recoil-action gun fires. For simplicity's sake, this animation doesn't show the cartridge loading, extraction and ejection mechanisms.

The first automatic machine guns had recoil-based systems. When you propel a bullet down the barrel, the forward force of the bullet has an opposite force that pushes the gun backward. In a gun built like a revolver, this recoil force just pushes the gun back at the shooter. But in a recoil-based machine gun, moving mechanisms inside the gun absorb some of this recoil force.

Here's the process: To prepare this gun to fire, you pull the breech bolt (1) back, so it pushes in the rear spring (2). The trigger sear (3) catches onto the bolt and holds it in place. The feed system runs an ammunition belt through the gun, loading a cartridge into the breech (more on this later). When you pull the trigger, it releases the bolt, and the spring drives the bolt forward. The bolt pushes the cartridge from the breech into the chamber. The impact of the bolt firing pin on the cartridge ignites the primer, which explodes the propellant, which drives the bullet down the barrel.

The barrel and the bolt have a locking mechanism that fastens them together on impact. In this gun, both the bolt and the barrel can move freely in the gun housing. The force of the moving bullet applies an opposite force on the barrel, pushing it and the bolt backward. As the bolt and barrel slide backward, they move past a metal piece that unlocks them. When the pieces separate, the barrel spring (4) pushes the barrel forward, while the bolt keeps moving backward.

The bolt is connected to an extractor, which removes the spent shell from the barrel. In a typical system, the extractor has a small lip that grips onto a narrow rim at the base of the shell. As the bolt recoils, the extractor slides with it, pulling the empty shell backward.

The backward motion of the bolt also activates the ejection system. The ejector's job is to remove the spent shell from the extractor and drive it out of an ejection port.

When the spent shell is extracted, the feeding system can load a new cartridge into the breech. If you keep the trigger depressed, the rear spring will drive the bolt against the new cartridge, starting the whole cycle over again. If you release the trigger, the sear will catch hold of the bolt and keep it from swinging forward.

Machine Gun Blowback Systems

Click and hold the trigger to see how a blowback-action gun fires. For simplicity's sake, this animation doesn't show the cartridge loading, extraction and ejection mechanisms. See the "Machine Gun Feeding: Belt System" section to find out how these components work.

A blowback system is something like a recoil system, except that the barrel is fixed in the gun housing, and the barrel and bolt don't lock together. You can see how this mechanism works in the diagram below.

This gun has a sliding bolt (3) held in place by a spring-driven cartridge magazine (5), and a trigger mechanism (1). When you slide the bolt back, the trigger sear (2) holds it in place. When you pull the trigger, the sear releases the bolt, and the spring drives it forward. After the bolt chambers the cartridge, the firing pin sets off the primer, which ignites the propellant.

The explosive gas from the cartridge drives the bullet down the barrel. At the same time, the gas pressure pushes in the opposite direction, forcing the bolt backward. As in the recoil system, an extractor pulls the shell out of the barrel, and the ejector forces it out of the gun. A new cartridge lines up in front of the bolt just before the spring pushes the bolt forward, starting the process all over again. This continues as long as you hold the trigger down and there's ammunition feeding into the system.

Click and hold the trigger to see how a gas-action gun fires. For simplicity's sake, this animation doesn't show the cartridge loading, extraction and ejection mechanisms. See the "Machine Gun Feeding: Belt System" section to find out how these components work.

The gas system is similar to the blowback system, but it has some additional pieces. The main addition is a narrow piston attached to the bolt, which slides back and forth in a cylinder positioned above the gun barrel. You can see how this system works in the diagram below.

This gun is basically the same as one using the blowback system, but the rear force of the explosion doesn't propel the bolt backward. Instead, the forward gas pressure pushes the bolt back. When the bolt swings forward to fire a cartridge, it locks onto the barrel. Once the bullet makes its way down the barrel, the expanding gases can bleed into the cylinder above the barrel. This gas pressure pushes the piston backward, moving it along the bottom of the bolt. The sliding piston first unlocks the bolt from the barrel, and then pushes the bolt back so a new cartridge can enter the breech.

The diagrams we've presented only depict particular examples of how these systems work. There are hundreds of machine gun models in existence, each with its own specific firing mechanism. These guns differ in a number of other ways as well. In the next two sections, we'll look at some of the key differences between various machine gun models.

Machine Gun Feeding: Spring and Hopper System

One of the main differences between different machine gun models is the loading mechanism. The early manual machine guns, such as the Gatling gun, used a device called the ammunition hopper. Hoppers are just metal boxes containing loose individual cartridges that fit on top of the machine gun mechanism. One by one, the cartridges fall out of the hopper and into the breech. Hoppers can hold a good amount of ammunition and they're easy to reload even while the gun is firing, but they are fairly cumbersome and only work if the gun is positioned right side up.

The hopper system was replaced by the belt-fed system, which helps control the ammunition's movement into the gun. Ammunition is contained on a long belt, which the operator holds, or is contained in a bag or box. After a round is fired, it moves out of the way, and a new round slips into place.

Another system is the spring-operated magazine. In this system, a spring pushes cartridges in a magazine casing up into the breech. The main advantages of this mechanism are that it's reliable, lightweight and easy to use. The main disadvantage is that it can only hold a relatively small amount of ammunition.

Read on for more information about the belt system's advantages.

Heavy belt-fed machine guns, usually mounted on a tripod or a vehicle, may need more than one operator. Individual troops usually carry light weapons, with extendible bipods or tripods for stability. Smaller automatic guns that use cartridge magazines are classified as automatic rifles, assault rifles or submachine guns. In a general sense, the term "machine gun" describes all automatic weapons, including these smaller weapons, but it's also used to describe heavy belt-fed guns specifically.

Machine Gun Feeding: Belt System

Top-view diagram of a common feed mechanism.

For sheer volume of ammunition, the belt system is usually the best option. Ammunition belts consist of a long string of cartridges fastened together with pieces of canvas or, more often, attached by small metal links. Guns that use this sort of ammo have a feed mechanism driven by the recoil motion of the bolt.

The bolt (1) in this gun has a small cam roller (5) on top of it. As the bolt moves, the cam roller slides back and forth in a long, grooved feedcam piece (2). When the cam roller slides forward, it pushes the feed cam to the right against a return spring (6). When the cam roller slides backward, the spring pushes the cam back to the left. The feed cam lever is attached to a spring-loaded pawl (8), a curved gripper that rests on top of the ammunition belt. As the cam and lever move, the pawl moves out, grabs onto a cartridge and pulls the belt through the gun. When the bolt moves forward, it pushes the next cartridge into the chamber.

The feed system drives the ammunition belt through cartridge guides (2) just above the breech. As the bolt slides forward, the top of it pushes on the next cartridge in line. This drives the cartridge out of the belt, against the chambering ramp (3). The chambering ramp forces the cartridge down in front of the bolt. The bolt has a small extractor, which grips the base of the cartridge shell when the cartridge slides into place. As the cartridge slides in front of the bolt, it depresses the spring-loaded ejector (6).

When the firing pin hits the primer, propelling the bullet down the barrel, the explosive force drives the operating rod and attached bolt backward. When the shell clears the chamber wall, the ejector springs forward, popping the shell out of the gun through the ejection port. This system lets you fire continuously without reloading.

Click and hold the trigger to see how the loading and ejection system works.

The basic mechanism of the machine gun has remained the same for more than a hundred years, but gun manufacturers are continually adding new modifications. One modern design transforms from a box to a gun with the single push of a button [source: Sofge]. In addition, new lightweight small arms technologies (LSAT) are made of lighter materials that could reduce the weight of machine guns and their ammunition by 40 percent.

Whether or not you've ever held a machine gun or even seen one, this powerful device has had a profound effect on your life. Machine guns have had a hand in dissolving nations, repressing revolutions, overthrowing governments and ending wars. In no uncertain terms, the machine gun is one of the most important military developments in the history of man. For additional information about machine guns and related topics, head to the links on the following page.

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