Although shotguns have changed a great deal since they were first invented, the terms used for their parts have changed very little. All modern shotguns have three basic groups of parts: action, stock, and barrel.
Action: The action is the heart of the firearm—the moving parts that load and fire the ammunition and eject the shells. There are several types of shotgun actions.
Stock: The stock is the part of the firearm that is held by the shooter. The stock also serves as the platform for supporting the action and the barrel.
Barrel: The barrel is the metal tube that the projectile travels through as a result of pressure from burning gunpowder, compressed air, or other like means. The barrel also guides the projectile in the intended direction.