What role do expanding gases play when a rifle is fired?

When a rifle is fired, expanding gases play a crucial role in propelling the bullet out of the cartridge and down the barrel. This process begins when the gunpowder inside the cartridge ignites and generates a rapid increase in pressure due to the heat and expansion of the gases produced. As these gases expand, they create force that pushes against the base of the bullet seated in the cartridge.

This force is what ultimately drives the bullet forward, overcoming the resistance of friction from the barrel. The speed and energy with which the bullet exits the barrel are largely a direct result of the rapid expansion of these gases. Understanding this function is important for safe and effective marksmanship, as well as for discussing the mechanics of how firearms operate.