Which of the following describes the heart of the firearm?

The heart of the firearm is described as the action. The action is a critical component that encompasses the mechanisms involved in loading, firing, and ejecting cartridges. It is essentially the operating system of the firearm, responsible for chambering rounds, extracting fired cases, and resetting the firing mechanism.

A well-functioning action ensures that the firearm operates smoothly and reliably with each shot fired. This includes various types of actions such as bolt, lever, pump, or semi-automatic. In this sense, understanding the action is crucial for safe handling and effective usage of the firearm, making it the core component that dictates how the firearm operates.

While the barrel serves as the pathway for the bullet, the stock provides the structural support and grip, and the trigger is the mechanism that initiates the firing process, none of these components would be functional without a properly functioning action.