The cartridge is the entire pre-assembled firearm packaging referred to as a bullet. The bullet is a projectile that’s housed inside a cartridge.
Ammunition is a cartridge composed of shells, propellant, primer, and projectiles commonly used in firearms. The standard ammunition comprises the following basic components: Cartridge Case, primer and primer cap, powder or propellant, wads, and the projectile.
This article further deals with the various components of the cartridge in detail.
Cartridge Case of Bullets
A cartridge case is also known as the shell after its contents are discharged. It provides housing for various components of the cartridge. It is usually made up of brass for rifle, pistol, and revolver ammunition.
For shotgun, it is made up of several layers of thin paper, which are tightly compressed. The base of the paper shell is made up of brass. Plastic shells are also manufactured. Cartridge cases are classified into three major groups based on various factors.
- Based on the Shape of Cartridge
- Straight cased: The case diameter is approximately equivalent along its length. It is meant for low-velocity weapons.
- Bottle-necked: The cartridge case is wide at the body but reduces in diameter near the mouth of the cartridge case. It is meant for a high-velocity weapon.
- Tapered neck– These types of cartridges are wide at the base and narrow down along the length.
- Based on the Configuration of the Base of the Cartridge
- Rimmed: These types of cartridges have a flange at the base, which is larger than the diameter of the body of the cartridge case. Most of the revolver ammunition has rimmed cartridges.
- Semi-Rimmed: These have a slightly larger flange than the diameter of the cartridge case and a groove around the case body just in front of the flange.
- Rimless: In these cartridge cases, the flange diameter is the same as the body of the case, and there is also the presence of a groove on the body just in front of the flange.
- Rebated– This cartridge case has an extractor flange that is less in diameter than the diameter of the cartridge case.
- Belted Case: These types of cases have raised belts encircling the base of the cartridge.
- Based on the Position of the Firing Pin
- Rimfires: These firearms have primer on the rim of the cartridge. These are limited to low-pressure loads.
- Centrefire: In this, the primer is present in the center of the cartridge case. They are used in rifles, shotguns, and handguns.
The primer cap contains the primer mixture, which gets sandwiched between the anvil and the firing pin. When the firing pin strikes on it with force, it gives rise to a hot piercing flame, which initiates the main charge.
The main ingredient of the primer in the past was either mercury fulminate or lead azide. The primers which are used nowadays contain compounds of lead, antimony, and barium.
To propel the bullet or shot charge through the barrel and then through the sir, a certain force is necessary. The powder charge provides this force. The powder charge gets ignited through primer and converts into the gas at a very rapid rate. The generated gas, under compression, develops pressure in the cartridge and finally forces out of the barrel, propelling the projectile. The three types of propellant charge known are black powder, smokeless powder, and semi smokeless powder.
Wads are used in the cartridge primarily to keep the propellant and the shot charge in their respective positions. In addition, they seal the barrel to prevent the escape of gases and, consequently, their respective reduction in the velocity.
In shotgun cartridges, several wads are used, which include over powder wad, a cushion wad, undershot wad, and overshot wad. Cushion wads are made from felt, cork, or cardboard, whereas the other wads are made of special quality cardboard.
In shotgun cartridges, the projectile consists of small lead balls or pellets. All shots, except in the very large sizes, are made by dropping molten lead from a high tower into water and, hence, drop shots.
In rifles, revolvers, and pistols, the projectiles consist of a single bullet that fits the bore size. Bullets are made of lead, alloyed with tin or antimony.
Various components of the cartridge have distinct functions and compositions. Knowing about these different compositions helps the investigating officers to determine the type of cartridge that helps to link it to the firearm used to fire.