What part of a firearm is responsible for loading, firing, and ejecting cartridges?

The action of a firearm is the integral component responsible for loading, firing, and ejecting cartridges. Essentially, it is the mechanism that holds the bolt and operates the firing cycle. When you operate the action, it brings a fresh cartridge into the chamber from the magazine, aligns it, and preps for firing. After firing, the action also facilitates the extraction and ejection of the spent cartridge, making it ready for the next shot.

The other components, such as the barrel, stock, and trigger, have distinct functions: the barrel is where the bullet travels upon firing, the stock provides structural support and stability, and the trigger is the part that releases the firing mechanism when pulled. Therefore, the action is essential for the overall operation of the firearm, tying together the functions of loading, firing, and ejection.