What is referred to as the metal housing for the working parts of a firearm's action?

The metal housing for the working parts of a firearm's action is known as the receiver. The receiver serves as the central component of the firearm, housing critical mechanisms such as the trigger, firing pin, and bolt. It plays a vital role in the operation of the gun, as it connects various parts that make the firearm functional.

In contrast, the barrel is the part of the firearm through which the bullet travels when fired, while the stock provides support and stability for the shooter to hold and aim the firearm. The chamber is a specific part of the receiver where the cartridge is inserted before firing, but it doesn't encompass the entire action of the firearm. Therefore, while all these parts are integral to a firearm's operation, the receiver is specifically defined as the metal housing for the working components of the action.