What is a cartridge used for in firearms?

A cartridge is essentially a self-contained unit of ammunition used in firearms. It consists of several components, including a projectile (bullet), gunpowder (propellant), and a primer, all housed within a casing. When a firearm is fired, the trigger releases the firing pin, striking the primer, which ignites the gunpowder and propels the bullet out of the barrel. This process is fundamental to the operation of firearms, making the cartridge a crucial element in providing the necessary ammunition for firing.

The other options relate to functions or components that do not accurately describe the role of a cartridge. Stabilizing the firearm involves aspects like the design of the gun and how it is held, not the cartridge itself. The handle of a firearm refers to the grip or stock, while the barrel is a separate component designed to guide the bullet, not something housed by the cartridge. Understanding the function of a cartridge is vital for safe and effective firearm use.