The primer in ammunition serves what purpose?

The primer in ammunition plays a crucial role in the firing process by igniting the ignitable material within the cartridge. When the firing pin strikes the primer, it creates a small explosion that ignites the gunpowder inside the cartridge case. This ignition is essential for propelling the bullet out of the barrel of the firearm.

Understanding this function highlights the primer's importance as a component of ammunition, which is designed to ensure reliable ignition under various conditions. The other options do not accurately describe the role of the primer: the bullet's weight is determined by its design and material, gunpowder is stored in the case itself rather than the primer, and trajectory stabilization is influenced by factors such as bullet design and rifling, not the primer.