What mechanism typically ejects the spent cartridge after firing a round?

The correct answer, the bolt system, plays a crucial role in the operation of a firearm, particularly in semi-automatic and automatic weapons. After a round is fired, the energy generated by the explosion propels the bullet forward and also exerts force on the spent cartridge casing. The bolt system is responsible for moving backward under this force, which simultaneously unlocks and ejects the spent cartridge from the chamber.

Once the cartridge is ejected, the bolt system also prepares to chamber a new round from the magazine. This entire sequence is vital for the continuous operation of firearms that rely on self-loading mechanisms. The ejection of the cartridge relies on the bolt's movement, making it essential for the firearm's cycling process.

The other systems mentioned, such as the gas system and recoil system, contribute to the overarching process of firearm operation but do not directly handle the ejection of the spent cartridge. The gas system may use gas from the fired round to cycle the action, while the recoil system helps manage the backward motion when the firearm is fired. The trigger mechanism, on the other hand, is solely responsible for firing the weapon, not for the ejection of cartridges. Understanding these distinctions highlights the importance of the bolt system in the functioning of firearms.