The Machine Gun's Impact on Modern Warfare

Experts regard the machine gun as one of the most pivotal inventions of the last century. It played a crucial role in shaping the intense, relentless nature of both World Wars and continues to influence modern conflicts.

Unlike earlier firearms, which required manual loading and firing, the machine gun allowed a single soldier to unleash a torrent of bullets, mowing down entire squads with continuous fire. The weapon would keep firing rapidly until the operator released the trigger or the ammunition ran out.

The advent of this weapon forced militaries to develop heavy artillery, like tanks, to endure its devastating firepower. This one weapon dramatically changed warfare tactics, enabling small units to combat like large battalions and amplifying the potential for mass casualties.

Given their significant impact on history, it's fascinating how deceptively simple machine guns can be. These weapons are wonders of engineering precision, yet they operate based on a few fundamental principles. This article will explore the basic mechanisms that allow machine guns to unleash bullets at such rapid rates.

Ballistic Insights: The Barrel

To grasp how machine guns function, it's helpful to first understand firearms in general. Most guns follow one basic principle: explosive force propels a projectile down a barrel. The cannon, one of the earliest and simplest firearms, is a prime example of this concept.

The Structure of a Cannon

A cannon is essentially a metal tube with one closed end and one open end. The closed end features a small hole for a fuse. To load the cannon, you pour in gunpowder — a blend of charcoal, sulfur, and potassium nitrate — followed by a cannonball.

The gunpowder and cannonball rest in the breech, the rear section of the bore, which is the cannon's open end. To ready the cannon for firing, you insert a fuse (a piece of flammable material) through the hole, ensuring it reaches the gunpowder.

To fire the cannon, simply ignite the fuse. The flame travels along the fuse until it reaches the gunpowder.

The Power Behind Gunpowder

Gunpowder burns quickly when ignited, creating a large volume of hot gas. The gas exerts significantly more pressure on the gunpowder side of the cannonball than the surrounding air does on the opposite side, propelling the cannonball at high velocity.

The Early Firearms

The first handheld firearms were essentially compact cannons capable of firing only a single shot at a time. You would load gunpowder and a steel ball, then ignite it with a fuse. Over time, this primitive technology evolved into trigger-operated firearms, such as the flintlock and percussion cap guns.

Flintlock vs. Percussion Cap Systems

Flintlock guns ignited the gunpowder by generating a small spark, while percussion caps used mercuric fulminate, an explosive material that could be set off with a sharp impact. To load a percussion cap gun, you pour gunpowder into the breech, insert the projectile on top, and affix a mercuric fulminate cap to a small nipple.

To fire the weapon, you pull the hammer all the way back and squeeze the trigger. This releases the hammer, causing it to swing forward and strike the explosive cap. The cap ignites, sending a flame down a tube to the gunpowder. The resulting explosion pushes the projectile out of the barrel.

An Introduction to Bullet Cartridges

A key advancement in firearm technology was the bullet cartridge. In simple terms, a cartridge combines the projectile (bullet), propellant (like gunpowder), and primer (explosive cap) into a single metal casing. Cartridges are the foundation of most modern firearms. The recoil from the gun's bolt also activates the ejection system, which removes the spent shell from the extractor and forces it out through the ejection port.

Revolvers

Earlier, we saw that a cartridge consists of a primer, propellant, and projectile, all housed in one metal casing. This simple yet effective device is the cornerstone of most modern firearms. To explore its operation, let's examine a standard double-action revolver.

Design and Functionality

The revolver features a rotating cylinder with six chambers to hold six cartridges. When you pull the trigger, a sequence of actions takes place:

Strengths and Weaknesses of Revolvers

Clearly, this firearm is simpler to operate than earlier models like the flintlock or percussion cap guns. You can load six rounds at once and simply pull the trigger to fire.

Despite their advantages, revolvers still have some limitations. You must pull the trigger for each shot, and after firing six shots, you need to reload (though some modern models can hold up to 10 rounds). Additionally, you must manually eject the spent cartridges from the chambers.

Next, let's explore how firearm manufacturers addressed the challenges associated with using revolvers.

Machine Guns and Firearm Systems

During the 1800s, gun designers developed several mechanisms to solve the limitations of revolvers. Many of these early machine guns featured multiple barrels and firing hammers integrated into a single system.

The Gatling Gun: A Game Changer in Firepower

One of the most influential designs was the Gatling gun, created by Richard Jordan Gatling. This weapon, the first machine gun to achieve widespread use, featured six to ten rotating barrels arranged in a cylinder. Each barrel was equipped with its own breech and firing pin mechanism.

To operate the Gatling gun, the user turns a crank, which causes the barrels to rotate inside the cylinder. As each barrel moves to the top of the cylinder, it passes under an ammunition hopper or carousel magazine, where a new cartridge falls into the breech and loads the barrel.

Each firing pin is connected to a small cam head that locks into a slanted groove in the gun's frame. As the barrels rotate, the groove pulls the firing pin back, compressing a spring. Once a new cartridge is in place, the cam slides out of the groove, releasing the spring to propel the pin forward, striking the cartridge and firing the bullet. Spent shells are ejected when the barrel reaches the bottom of the cylinder.

The Gatling gun played a significant role in several 19th-century conflicts, but it wasn't until the early 1900s that the machine gun truly solidified its place as a formidable weapon on the battlefield.

Although the Gatling gun is often regarded as a machine gun due to its ability to fire a rapid succession of rounds, it is not a fully automatic weapon like modern general-purpose machine guns. To keep firing, you must continue cranking the handle.

The First Fully Automatic Machine Gun

The first truly automatic machine gun is attributed to the American inventor Hiram Maxim. Maxim's design could fire more than 500 rounds per minute, delivering the firepower equivalent to approximately 100 rifles.

The core concept behind Maxim’s gun, as well as the many machine gun designs that followed, was to harness the power generated by the cartridge's explosion to reload and cock the weapon after each shot. This process relies on three main mechanisms:

In the upcoming sections, we will delve into the details of each of these systems.

Machine Gun Recoil Systems

The earliest automatic machine guns were designed with recoil-based systems. When a bullet is propelled through the barrel, the force pushing the bullet forward creates an equal and opposite force that pushes the gun backward.

In a revolver-style firearm, this recoil force merely causes the gun to move backward towards the shooter. However, in a recoil-operated machine gun, internal mechanisms within the gun absorb some of this backward force.

Firing Mechanism and Bullet Propulsion

The process is as follows: To ready this gun for firing, you pull the breech bolt back, compressing the rear spring. The trigger sear then catches the bolt, holding it in place. The feed mechanism runs an ammunition belt through the gun, positioning a cartridge into the breech (more details on this later).

When the trigger is pulled, it releases the bolt, and the compressed spring forces the bolt forward. This motion pushes the cartridge from the breech into the chamber.

The firing pin at the tip of the bolt strikes the cartridge, igniting the primer. This explosion ignites the propellant, which propels the bullet down the barrel. A locking mechanism on both the barrel and the bolt secures them together during the impact.

Recoil Action, Shell Ejection and Continuous Firing

In this design, both the barrel and bolt are able to move freely within the housing. The energy from the bullet’s forward motion generates an opposing force on the barrel, pushing both the barrel and the bolt backward. As the bolt and barrel slide back, they pass a metal piece that disengages the locking mechanism.

As the pieces separate, the barrel spring pushes the barrel forward, while the bolt continues its backward motion. Attached to the bolt is an extractor that pulls the spent shell from the barrel. In a standard system, the extractor features a small lip that grips the narrow rim of the shell's base.

As the bolt moves backward, the extractor moves with it, pulling the empty shell in the same direction.

The recoil of the bolt also triggers the ejection system. The ejector’s role is to detach the spent shell from the extractor and force it out through an ejection port.

Once the spent shell is ejected, the feeding system can load a fresh cartridge into the breech. If the trigger remains pressed, the rear spring forces the bolt against the new cartridge, restarting the cycle. If you release the trigger, the sear catches the bolt, halting it from moving forward.

Machine Gun Blowback Systems

A blowback system operates similarly to a recoil system, but with a key difference: the barrel remains fixed in the gun housing, and the barrel and bolt do not lock together.

This firearm uses a sliding bolt, secured by a spring-driven cartridge magazine and a trigger mechanism. When the bolt is pulled back, the trigger sear locks it in place. Upon pulling the trigger, the sear releases the bolt, allowing the spring to push it forward. After the bolt chambers the cartridge, the firing pin ignites the primer, which triggers the propellant.

The explosive gas from the cartridge propels the bullet down the barrel. Simultaneously, the gas pressure pushes in the opposite direction, forcing the bolt to move backward.

As with the recoil system, an extractor pulls the shell from the barrel, and the ejector expels it from the firearm. A new cartridge positions itself in front of the bolt just before the spring pushes the bolt forward, restarting the cycle.

This process continues as long as the trigger is held down and ammunition is fed into the system.

Machine Gun Gas Systems

The gas system shares similarities with the blowback system but introduces a few extra components. The key addition is a small piston connected to the bolt, which moves back and forth inside a cylinder located above the gun barrel.

In this case, the mechanism operates similarly to the blowback system, except that the rearward force from the explosion does not push the bolt backward. Instead, the forward pressure from the gas moves the bolt in the opposite direction.

When the bolt moves forward to fire a cartridge, it locks into the barrel. After the bullet travels down the barrel, the expanding gases flow into the cylinder above the barrel. The gas pressure pushes the piston backward, moving it along the bottom of the bolt. The piston first unlocks the bolt from the barrel and then forces it backward to allow a new cartridge to be loaded into the breech.

The diagrams shown are only specific examples of how these systems function. Numerous machine gun models exist, each featuring its own distinct firing mechanism. These weapons also differ in a variety of other ways. In the next sections, we will explore some of the key distinctions between different machine gun models.

Machine Gun Feeding: Spring and Hopper System

A key distinction among various machine gun models lies in their loading mechanisms.

The Ammunition Hopper System

In the early manual machine guns like the Gatling gun, an ammunition hopper was used. This hopper is essentially a metal container filled with individual loose cartridges that sit atop the machine gun’s mechanism. As the gun operates, the cartridges fall one by one into the breech.

Hoppers can store a significant amount of ammunition and are relatively simple to reload while the gun is in use. However, they are quite bulky and function properly only when the gun is upright.

Transition to the Belt-fed System

The belt-fed system replaced the hopper system, offering better control over how ammunition feeds into the gun. The ammunition is stored on a continuous belt, either held by the operator or contained in a bag or box. Once a round is fired, it moves out of the way, allowing a fresh round to slip into position.

The Spring-operated Magazine System

Another type of feeding system is the spring-operated magazine. This mechanism uses a spring to push cartridges from a magazine into the breech. Its main advantages include reliability, light weight, and ease of use.

However, its major downside is that it has a limited ammunition capacity.

Mounted Machine Guns

Heavy, belt-fed machine guns, which are typically mounted on a tripod or vehicle, often require more than one operator. In contrast, soldiers usually carry lighter machine guns, equipped with extendable bipods or tripods to provide stability while firing.

Smaller automatic weapons that utilize cartridge magazines are classified as automatic rifles, assault rifles, or submachine guns. In a broader sense, the term 'machine gun' encompasses all automatic weapons, including these smaller firearms, but is also specifically used to refer to heavy, belt-fed guns.

Machine Gun Feeding: Belt System

For the highest volume of ammunition, the belt system is typically the most efficient choice. These belts consist of a continuous series of cartridges linked together with canvas pieces or, more commonly, small metal links. Guns using this type of ammunition feature a feed mechanism driven by the recoil motion of the bolt.

Mechanics of the Belt Feed System

In a belt-fed firearm, the bolt features a small cam roller on top. As the bolt moves, the cam roller slides back and forth within a long, grooved feed cam.

When the cam roller moves forward, it pushes the feed cam to the right, compressing a return spring. As the roller moves back, the spring forces the cam back to the left. The feed cam lever is connected to a spring-loaded pawl, which is a curved gripper that sits atop the ammunition belt.

As the cam and lever move, the pawl extends, grabs a cartridge, and pulls the belt through the firearm. When the bolt moves forward, it pushes the next cartridge into the chamber.

The feed system drives the ammunition belt through cartridge guides positioned just above the breech. As the bolt slides forward, its top pushes the next cartridge in line, ejecting it from the belt and directing it against the chambering ramp.

The chambering ramp pushes the cartridge down in front of the bolt. The bolt features a small extractor that grips the base of the cartridge shell as it slides into place. As the cartridge moves into position, it presses against the spring-loaded ejector.

When the firing pin strikes the primer, launching the bullet down the barrel, the explosive energy drives the operating rod and attached bolt backward. Once the shell clears the chamber wall, the ejector springs forward, expelling the shell out of the ejection port. This system allows for continuous fire without the need for reloading.

Evolution and Impact of Machine Guns

While the core mechanism of the machine gun has remained consistent for over a century, manufacturers continue to introduce new innovations. One modern design can transform from a box into a fully functioning gun with a simple push of a button [source: Sofge]. Additionally, new lightweight small arms technologies (LSAT) utilize lighter materials that could potentially reduce the weight of both the gun and its ammunition by 40%.

Whether or not you have ever held or even seen a machine gun, this formidable weapon has undoubtedly influenced your life. Machine guns have played a role in the fall of nations, the suppression of revolutions, the overthrow of governments, and the conclusion of wars—and in the wrong hands, they have led to tragic events. In no uncertain terms, the machine gun stands as one of the most significant military innovations in human history.