What are the differences between semi-automatic and automatic firearms?

The distinction between semi-automatic and automatic firearms is primarily based on their firing mechanics. Semi-automatic firearms are designed to fire one single round each time the trigger is pulled. After firing, they automatically cycle to load the next round into the chamber, but they do not fire again until the trigger is pulled once more. This characteristic allows for controlled and deliberate shooting, making them popular for civilian use in various contexts, including sport shooting and self-defense.

In contrast, automatic firearms are designed to continue firing as long as the trigger is held down. This capability allows for a rapid and continuous discharge of rounds until the trigger is released or the ammunition is exhausted. This fundamental difference in firing mechanism distinguishes the two types of firearms, with automatic firearms often being reserved for military or law enforcement applications, where sustained fire may be necessary.

The other statements in the choices do not accurately reflect the fundamental mechanics that define semi-automatic and automatic firearm operation, making the second option the effective characterization of their relationship.