What does the primer do in the firing process?

The primer's role in the firing process is crucial, as it is responsible for igniting the gunpowder contained within the cartridge. When the firing pin strikes the primer upon pulling the trigger, it creates a small explosion that produces sufficient heat and pressure to ignite the powder. This ignition then leads to the rapid expansion of gases generated by the burning powder, which propels the bullet down the barrel and ultimately out of the firearm.

By understanding the function of the primer in this context, it becomes evident how essential it is for the entire firing sequence. Other aspects of the firing process, such as ejection of the cartridge, chambering the next round, or cooling the barrel, involve different mechanical functions or systems within the firearm that do not relate directly to the ignition of the powder.