Definitions Shape the Framework
Federal firearms regulation turns on precise statutory definitions, because whether a rule applies to an object depends entirely on whether that object meets a defined term. A legal definition can diverge sharply from everyday usage, so reading the statutory language is essential. This overview explains the key defined terms.
"Firearm" Under the Gun Control Act
The Gun Control Act defines "firearm" to include not only weapons that expel a projectile by explosive action but also the frame or receiver of such a weapon, plus certain other items. This is why a bare receiver, with no barrel or stock, is itself regulated as a firearm. The definition reaches the regulated core component, not just the assembled weapon.
The Frame or Receiver
Because the frame or receiver is the regulated part, serialization and transfer rules attach to it rather than to interchangeable components like barrels or grips. Identifying which part is the receiver can be technical, and the ATF has issued rules clarifying it for modern multi-part designs. The receiver is the anchor to which the recordkeeping framework attaches.
"Firearm" Under the National Firearms Act
The National Firearms Act uses its own, narrower definition, listing the specific regulated items: machine guns, short-barreled rifles and shotguns, suppressors, destructive devices, and any other weapons. An object can be a "firearm" under one act's definition but treated differently under the other's. Which statute's definition applies determines which regime governs.
Antiques and Exclusions
Federal law generally excludes "antique firearms," broadly certain pre-1899 firearms and some replicas, from the definition of firearm, placing them outside much of the framework. The antique exclusion shows how a defined carve-out can remove an item from regulation entirely. Exclusions are as consequential as inclusions.
Worked Example
Suppose someone possesses a stripped lower receiver with no other parts. Under the Gun Control Act's definition it is a "firearm" because the receiver itself is regulated, so it must be serialized and transferred through the licensed channel, even though it cannot fire anything on its own. The definition, not the object's current capability, decides how the framework treats it.
A Common Misconception
People often assume "firearm" means only a complete, functional weapon. Legally the term can include a bare frame or receiver while separately excluding certain antiques that plainly can fire, so the statutory definition is both broader and narrower than intuition in different places. Reading the definition, not the object, is what tells you the rule.