How Revolvers Work

In 1856, Samuel Colt had to produce 150 guns a day to meet growing demand. See more gun pictures.
In 1856, Samuel Colt had to produce 150 guns a day to meet growing demand. See more gun pictures.
David De Lossy/Getty Images

In 1830, when he was only 16, Samuel Colt left home and took a job on a merchant ship bound for India. In his spare time, he toyed with designs for a new sort of gun -- one that could be fired repeatedly without reloading. While a number of repeating weapons had already been developed, none of them had caught on with the public, mostly because they were too complicated and cumbersome.

Inspired by a capstan mechanism on the ship, Colt developed a simple revolving ammunition cylinder. Initially, people weren't particularly impressed with the new weapon; but by the 1850s, Colt's company was enjoying phenomenal success. In 1856, he had to churn out 150 guns a day just to keep up with the growing demand!


The extremely simple, highly reliable weapon had a profound effect on life in the United States and later in the rest of the world. Armed with a revolver, anybody could kill another person in a matter of seconds. War, crime, law enforcement and even everyday arguments were infused with a new deadly element.

In this edition of HowStuffWorks, we'll look at the basic operating principle of the revolver to see why it remains such a popular weapon after more than 150 years on the market. We'll also look at the basic concepts behind firearms and check out a few of the important weapons that preceded the revolver.

Gun Basics and History

To understand how a revolver works, it helps to know something about guns in general. Almost every gun is based on the same 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, the rear part of the bore (the open space in the cannon). To prepare 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, you light the fuse. The flame travels along the fuse and finally reaches the gunpowder.


When you ignite gunpowder, it burns rapidly, 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.

The first handheld guns were essentially miniature cannons; you loaded some gunpowder and 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
A percussion-cap gun (left) and a flintlock gun (right), two important steps on the way to modern firearms

Flintlock guns ignited gun powder 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 a ball 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 ball out of the barrel. (Check out How Flintlock Guns Work for more information on these weapons.)

In the 1800s, the percussion-cap gun slowly gave way to the revolver, which only had to be reloaded every five or six shots instead of after each shot. In the next section, we'll see how this system works.

The Revolver

The first revolvers used gunpowder, balls and caps like the earlier percussion-cap pistols. The shooter would load each of the six chambers in the cylinder with gunpowder and a projectile, and place separate percussion caps on corresponding nipples. While the loading procedure was tedious, a shooter could have six rounds fully prepared ahead of time.

In the 1870s, these models were replaced by revolvers that used bullet cartridges instead of gunpowder and caps. 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.


In a modern revolver, cartridges are loaded into six chambers, each of which can be positioned in front of the gun's barrel. A spring-loaded hammer is positioned on the other side of the cylinder, in line with the barrel. The basic idea of the gun is to cock the hammer back, line up a new cartridge in between the hammer and the barrel and then release the hammer by pulling a trigger. The spring throws the hammer forward so it hits the primer. The primer explodes, igniting the propellant, which drives the bullet down the barrel.

The inside of the barrel is lined with spiraling grooves, which spin the bullet to give it stability. A longer barrel improves stability, since it spins the bullet for longer. Extending the barrel also increases the speed of the bullet, since the gas pressure accelerates the bullet for a longer period of time.

In early revolvers, a shooter had to pull the hammer back before each shot and then pull the trigger to release the hammer. In modern revolvers, simply pulling the trigger will force the hammer backward and then release it.

The sequence of events in each shot is very simple:

  • The trigger lever pushes the hammer backward.
  • As it moves backward, the hammer compresses a metal spring in the gun stock (the handle). The diagram above shows a coiled spring; uncoiled tension springs are also used in revolvers.
  • At the same time, a pawl attached to the trigger pushes on a ratchet to rotate the cylinder. This positions the next breech chamber in front of the gun barrel.
  • Another pawl lodges in a small depression on the cylinder. This stops the cylinder in a particular position so it is perfectly lined up with the barrel.
  • When the trigger lever is pushed all the way back, it releases the hammer.
  • The compressed spring drives the hammer forward. The firing pin on the hammer extends through the body of the gun and hits the primer. The primer explodes, igniting the propellant.
  • The propellant burns, releasing a large volume of gas. The gas pressure drives the bullet down the barrel. The gas pressure also causes the cartridge case to expand, temporarily sealing the breech. All of the expanding gas pushes forward rather than backward.
  • To reload the gun, the shooter swings the cylinder out and pushes on the ejector rod to operate the extractor in the middle of the cylinder. The extractor grabs the base of the spent shells and removes them from the cylinders.
  • To reload, the shooter can place individual cartridges into the chambers or load six at once with a speed loader (basically, a small metal holder with cartridges secured in the right position).

In double-action revolvers, the shooter can either pull the trigger to cock and fire or pull the hammer back ahead of time. The advantage of cocking the hammer first is that the trigger moves more easily when it is time to fire.

Obviously, a revolver is easier to use than a flintlock or a percussion-cap weapon. A shooter can load six shots at a time and only needs to pull the trigger to fire. But revolvers seem very limited next to newer technologies: The shooter must pull the trigger for every shot and stop to reload regularly. On the battlefield, the revolver can't possibly stand up to modern automatic weapons.

The enduring popularity of revolvers is due to the simplicity of their design. Everything fits together so well that the guns very rarely jam. And since they are made with a relatively small number of parts, they are relatively inexpensive to manufacture. For the home defender and criminals alike, it is an ideal, affordable weapon.

For more information on revolvers and other weapons, check out the links on the next page.