What does the powder in a cartridge do when ignited?

When the powder in a cartridge is ignited, it generates high-pressure gas. This process occurs when the primer is struck by the firing pin, causing the powder to combust. The rapid combustion transforms the solid powder into gas, which expands quickly and forces the bullet out of the casing and down the barrel of the firearm. The pressure generated from this gas is what propels the bullet forward at high speed.

Other options do not accurately describe the primary function of the powder. While sound is produced when the bullet is fired, it is a byproduct rather than a purpose of the powder. The powder does not offer structural support; instead, it is a combustible material essential for providing propulsion. Additionally, while the weight of the bullet is an important factor in its performance, the powder itself does not directly influence this characteristic. Its main role is to produce gas under pressure, which is critical for the firing process.