What component is NOT part of a round?

The trigger is a component that is part of the firearm itself, not a component of the cartridge or round. A round consists of several key elements that work together when fired, including the cartridge case, primer, and bullet. The cartridge case holds all the components, the primer ignites the propellant, and the bullet is the projectile that is expelled when the gun is fired. Therefore, the trigger, which is involved in the firing mechanism of the firearm, does not belong to the round or cartridge. Understanding this distinction helps clarify the various parts of a firearm and its ammunition, which is essential for effective law enforcement and safety practices.