The First Guns

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

A percussion cap gun (left) and a flintlock gun (right), two important steps on the way to modern firearms. To learn more about these weapons, check out How Flintlock Guns Work.

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 poured gunpowder into the breech, stuffed the projectile in on top of it, and placed a mercuric fulminate cap on top of a small nipple. To fire the gun, you cocked a hammer all the way back, and pulled the gun's trigger. The trigger released the hammer, which swung forward onto the explosive cap. The cap ignited, shooting a small flame down a tube to the gunpowder. The gunpowder exploded, launching the projectile out of the barrel. (Check out How Flintlock Guns Work for more information on these weapons.)

Ballistic Background: Cartridge
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.

Needless to say, cartridges were a phenomenal success. In fact, they form the basis for most modern firearms. In the next section, we'll see how these sorts of weapons work.

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. Will discuss this in more detail later. But first, let's look at how all of this works -- in a revolver.

Revolvers

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.

Click on the trigger to see how a revolver fires.

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

1. 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.
2. When you pull the trigger all the way back, the lever releases the hammer.
3. The compressed spring drives the hammer forward.
4. The hammer slams into the primer at the back of the cartridge, igniting the primer.
5. The primer sets off the propellent.
6. The exploding propellent drives the bullet out of the gun at high speed.

The inside of the barrel has a spiral groove cut into it, which serves to spin the bullet as it exits the gun. This gives the bullet better stability as it flies through the air, increasing 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.

Revolvers, which come in a range of shapes and sizes, are one of the most popular gun designs of all time. Their design is so simple that they almost never jam or misfire.

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. You also have to eject the empty shells from the cylinders manually.

Now let's take a look at how gun manufacturers addressed the problems inherent in revolvers.

Machine Guns: Guns and Gun Systems

Gatling Gun
In the 1800s, gun manufacturers worked up a number of mechanisms to address the problems of 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. You can see how this weapon works in the diagram below.

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 carrousel 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 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.

Photo courtesy Department of Defense A U.S. airman fires a GAU-17 mini-gun from a UH-1 Huey during training exercises in Australia. Mini-guns are modern updates of the Gatling gun, with an electric motor, rather than a hand-crank, to rotate the barrels.

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. In the next section, we'll look at the next major step in machine gun evolution.

Fully Automatic
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 is not fully automatic. You have to keep cranking if you want to keep shooting. The first fully automatic machine gun is 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.

Hiram Maxim and one of his early machine gun designs: When Maxim introduced his weapon to the British army in 1885, he changed the battlefield forever.

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:

• Recoil systems
• Blowback systems
• Gas mechanisms

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

Machine Guns: Recoil Systems

The first automatic machine guns had a recoil-based system. In nature, every action has an equal and opposite reaction. This principle is responsible for the recoil effect in guns. 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. You can see how this works in the diagram below.

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. See the "Machine Gun Feeding: Belt System" section to find out how these components work.

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. There are a number of extractor systems in modern guns, but the basic idea in all of them is fairly simple. 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 (more on this later).

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.