What constitutes a "firearm part" according to firearm regulations?

A "firearm part" refers to components that are essential to the operation or structure of a firearm, and according to firearm regulations, certain parts play significant roles in its functionality.

The slide, bolt, or breech block of a firearm are critical components responsible for cycling the action, which includes loading, firing, and ejecting cartridges. These parts are integral to the shooting process and are specifically noted in regulations as they can affect the overall operation and legality of a firearm. When assembled with other parts, they enable the firearm to function as intended.

In contrast, while the grip, magazine, and barrel also serve important roles in the construction and use of a firearm, they do not relate as directly to the firing mechanism and operation as the slide, bolt, or breech block do. The grip is primarily a support structure, the magazine serves as a storage for ammunition, and while the barrel is essential for directing the bullet, it does not partake in the action mechanics involved in firing. Therefore, the specific mention of the slide, bolt, or breech block underscores their categorization as key firearm parts under the law.