A shell casing is a piece of ammunition that is made of metal. It is often brass, but it can be made of other metals as well, and the more durable the better. Shell casings can be made from any kind of ammunition that is fired from a pistol, rifle or shotgun. It is not a bullet, but it is a piece of the larger ammunition mechanism that is loaded into the chamber to be shot. To understand the role of the shell casing, it is better to understand the way that a gun works, and its purpose in firing.
How a Gun Works
A gun is an instrument to fire bullets, but much of the explosion actually comes from the bullet. A bullet is like a miniature firework that is rigged to explode. It comes in three pieces, the primer, the propellant, and the proper part of the bullet. These sections are housed inside a brass jacket called a shell casing.
When a bullet is fired
The gun works by hammering a tiny pin into the end of the ammunition and igniting the primer, which is a small explosive charge. The spark ignites the propellent, which is like a tiny version of setting a match to gasoline. This causes a much bigger fire or explosion. The casing is designed to force the explosion to go only one direction, which is forward and out the barrel of the gun. The casing surrounds the entire bullet area, and is like a metal cylinder that is wrapped around the bullet, its primmer, and its propellant. It is usually hollow inside to make room for the propellant liquid or gas, and the end of it is flat with a small dimple or indentation that makes room for the pin to strike the primer as directly as possible. The casing is thickest on this strike plate to protect the person firing, so that things only explode away from the shooter and not toward them.
Finding Shell Casings
Shell casings are often found at the sites of places where guns were fired. They are expelled from a gun, usually when a new bullet is loaded into the chamber to be fired. When crime scenes or hunting areas are searched after bullets or shot has been fired, casings are a common remnant in the area. With bullets, the casings are entirely metal, and usually reasonably small. Shot casings are larger, with a brass strikeplate on the bottom and a plastic sleeve that held the shot attached to it.
