What role does powder play in the firing of a bullet?

The role of powder in the firing of a bullet is pivotal, as it functions to propel the bullet out of the casing. In a firearm, when the trigger is pulled, the firing pin strikes the primer, which ignites the powder contained in the cartridge. This ignition causes a rapid expansion of gases—the result of the combustion of the gunpowder—which builds pressure within the cartridge. The increasing pressure forces the bullet forward and out of the barrel at high velocity.

Understanding this function is essential for grasping the mechanics of firearms. The powder does not provide structural support, ignite any other materials as an explosive igniter, or serve as a container for the bullet; instead, its primary role is to generate the energy needed for propulsion during the firing sequence.