Cartridge Firing Sequence
Cartridge Firing Sequence
The process of firing the gun starts when you load the cartridge into the chamber of the firearm. After loading the cartridge, you aim the firearm and pull the trigger. The mechanics of the gun very, but a firing pin eventually strikes the primer, which ignites the propellant.
- A firing pin strikes and ignites the primer. A Primer is a primary explosive which produces heat
- The priming compound ignites the powder (gunpowder).
- The burning power forms gases.
- The expanding gases propel the projectile (shot or bullet) down the barrel and out the muzzle.
The spark from the primer ignites the gunpowder. Gas converted from the burning powder rapidly expands in the cartridge. The expanding gas forces the bullet out of the cartridge and down the barrel with great speed. The rifling in the barrel causes the bullet to spin as it travels out of the barrel.
The primer is where all the action starts. It’s the small round metal object located in the centre of the base of the cartridge. Just like the caps for a toy cap gun, a primer is filled with a chemical compound that explodes when it’s smashed. So when the firing pin—a rod that’s driven forward when you pull the trigger—impacts and dents the base of the primer, the compound inside of the primer explodes. This (relatively) small conflagration creates a flame that is directed through a small hole and into the main body of the cartridge case, igniting the powder. (More on that in a bit.)
The case is the container that holds the powder. Think of the case as a container of sorts for all the other things that make up a cartridge. The primer fits into a small pocket at the base of the case; the powder resides inside of it, and the bullet is seated at the opposite open end of the cartridge case.
The case is the part that is flung out of your semi-automatic gun (or dropped or extracted from your revolver or bolt-action rifle) after you fire.
If you shake a cartridge, you’ll feel and hear something akin to sand rustling around inside. That’s the powder. Called “propellant” by gun geeks, it’s a specially formulated compound that burns really, really fast—faster than rocket fuel, or even marshmallows over a hot fire. In fact, it burns so fast that many people assume it explodes. We don’t need to get into the technicalities here, just know that this rapidly burning powder doesn’t technically explode. Rather, the fast burn creates hot, expanding gas that develops a lot of pressure really quickly inside of the cartridge.
All that gas has to go somewhere, so it follows the path of least resistance and pushes the bullet out of the case and down the barrel. As the powder burns, and pressure builds, the bullet moves ever faster down the barrel until it escapes the confines of your gun. The pressurized gases that escape the barrel just behind the bullet
At this point, the bullet part is pretty self-explanatory. It’s the only part of the cartridge that travels forward when you fire the gun. Also called the projectile, the bullet is what does the work downrange.
Bullets are made from different materials and come in various shapes and sizes. Most handgun bullets have a copper exterior (called the jacket) that surrounds a lead core. However, some bullets are made entirely from lead, while others might be made entirely from copper. The reason for these differences might be cost, or the desire for a specific effect when the bullet hits something.
Different bullets in the same calibre family might also be shaped very differently, depending on how you want them to behave. Rifle bullets for long-range shooting will be long and skinny, making them more aerodynamic and less affected by the wind. Self-defense or hunting bullets might be constructed in such a way as to expand when they strike their target. Match or competition bullets might get extra special attention during manufacturing to ensure that they are perfectly shaped, and each one is identical to the others. That ensures that each shot will hit exactly where it’s supposed to, assuming the shooter executes the shot the same way each time.
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Eric Beer | BC Firearm Academy
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