How Guns Work: Learn the Parts of a Gun

By: Marshall Brain  | 
A young woman with her instructor practicing how to shoot a gun at a shooting range.
Guns permeate society; police officers carry them, wars are fought with them and ordinary citizens own them. Now you can learn all the different components of guns. RichLegg / Getty Images

Guns permeate society — police officers carry them, wars are fought with them, ordinary citizens own them. How this complicated piece of machinery works, however, can be a bit of a mystery. In this article, we'll explore the basic parts of a gun to better understand how a firearm works.

There are many types of firearms, but the most commonly operated by civilians include the handgun, the rifle, and the shotgun. These modern firearms all have three basic parts: the action, the stock, and the barrel. Within these common parts, there is a lot of variation.


  1. Action
  2. Stock
  3. Barrel


The action is the part of the gun containing the moving parts involved in loading and firing ammunition and expelling the spent cartridge or shells. There are multiple types of actions.

Trigger Mechanism

The best-known component of the action is probably the trigger. The trigger is the part of a larger trigger mechanism that may also contain:


  • Trigger guard: The trigger guard is a frame that houses the trigger and prevents accidental discharge. Most guns have an additional safety in the form of a switch or lever that can deactivate the gun by disconnecting the trigger from the firing mechanism.
  • Sear: The sear holds the bolt, hammer or striker (firing pin) until the shooter applies sufficient pressure to the trigger.
  • Hammer: In firearms that have them, pulling the trigger activates the hammer, which then strikes the cartridge primer or activates the firing pin.
Semi-automatic Pistols

The trigger system on an automatic or semi-automatic pistol has a few special features:

  • Slide: A semi-automatic pistol typically has a slide located on top of the barrel. The slide moves via recoil energy: When you fire the gun, the slide recoils backwards. It then hits a recoil spring, which pushes it forwards.
  • Magazine: The word "magazine" can refer to any type of ammunition storage. On a handgun, the magazine stores cartridges. The magazine release on a semi-auto handgun allows the user to remove the magazine for easy loading. When the recoil spring pushes the slide forward via a recoil spring, it loads the next cartridge from the magazine into the chamber.
  • Slide lock: When the last cartridges of the magazine have been used, the slide lock (also known as the slide stop) will activate.

In a revolver, the ammunition is stored in a cylinder. The cylinder contains multiple chambers, each capable of holding a single cartridge. When you activate the firing mechanism, the cylinder revolves (hence the name "revolver"), aligning the next chamber with the barrel.

Modern revolvers typically have a release for easy reloading.



The stock is the part of the gun the action and barrel are mounted to. Rifles and shotguns have a butt stock or shoulder stock designed to be placed against the shooter's shoulder. Instead of a shoulder stock, handguns have a grip, held in the shooter's hand.

The stock typically extends from the grip (the part of the gun the shooter holds) toward the shooter's body.



The barrel is the metal tube the bullet travels through. At the rear end of the barrel is the chamber, which holds the cartridge. When you fire a gun, the bullet or other ammunition is released from the chamber and travels through the barrel.

The bullet exits through the muzzle, located at the front end of the barrel. In an old-fashioned muzzle-loaded gun, the ammunition is loaded into the muzzle rather than the chamber.


Long guns like rifles and shotguns have long barrels (at least 16 inches or 40.6 centimeters long), while modern handguns (like a a semi-automatic pistol), have shorter barrels (less than 15 inches or 38 centimeters long).

Designed for shooting at a distance, long guns typically have front and rear sights mounted on the barrel to help the shooter aim at the target.