What component within a cartridge is responsible for the bullet's propulsion?

The component within a cartridge that is responsible for propelling the bullet is the gunpowder, also known as the propellant. When a firearm is discharged, the primer ignites the gunpowder, causing a rapid expansion of gases. This expansion builds up pressure inside the cartridge, which forces the bullet out of the casing and down the barrel of the firearm at high speed.

Understanding this process is crucial for grasping how firearms operate and the role of each component in a cartridge. The bullet, while essential for the projectile aspect, does not create propulsion itself; it is the result of the explosive reaction of the gunpowder that provides the necessary force to propel the bullet forward. Similarly, the casing holds the bullet, primer, and gunpowder together, but it does not contribute to the propulsion. The primer ignites but doesn't provide the sustained energy needed for propulsion, making gunpowder the key component in driving the bullet from the firearm.