A Class 3 weapon is the common (and technically incorrect) name for a firearm regulated under the National Firearms Act of 1934. The label actually refers to a federal dealer tax classification, not the weapon itself, but in everyday use it describes six categories of tightly regulated firearms: machine guns, short-barreled rifles, short-barreled shotguns, suppressors, destructive devices, and a catch-all group called “any other weapons.” The correct term is NFA firearm or Title II firearm.
Where the “Class 3” Label Comes From
“Class 3” is a Special Occupational Taxpayer (SOT) classification for federally licensed firearms dealers who pay an annual $500 tax for the privilege of buying and selling NFA-regulated items.1Bureau of Alcohol, Tobacco, Firearms and Explosives. Special Tax Registration and Return National Firearms Act (NFA) Because ordinary buyers acquire these firearms through Class 3 dealers, the dealer’s tax class became shorthand for the product being sold. The weapons themselves have no “class.” Federal law calls them NFA firearms, and that’s the term used in the statutes, regulations, and forms.
The Six Categories of NFA Firearms
Federal law defines each category with specific technical criteria in 26 U.S.C. § 5845.2Office of the Law Revision Counsel. 26 USC 5845 – Definitions A firearm either meets the definition or it doesn’t; there is no discretion.
- Machine guns. Any firearm that fires more than one round with a single trigger pull. The definition also covers the receiver of such a weapon, conversion parts, and any combination of parts that could be assembled into one.
- Short-barreled rifles (SBRs). A rifle with a barrel under 16 inches or an overall length under 26 inches. A weapon modified from a rifle to meet either measurement also qualifies.
- Short-barreled shotguns (SBSs). A shotgun with a barrel under 18 inches or an overall length under 26 inches, or a shotgun modified to meet either threshold.
- Suppressors (silencers). Any device that reduces the sound of a gunshot, along with individual components designed solely for building or repairing one.3Office of the Law Revision Counsel. 18 USC 921 – Definitions
- Destructive devices. Explosive ordnance like bombs, grenades, mines, and rockets with a propellant charge over four ounces. The category also includes firearms with a bore diameter over half an inch, though shotguns recognized as suitable for sporting purposes are exempt.
- Any other weapons (AOWs). A catch-all for concealable devices that fire using an explosive charge but don’t fit the other categories. Pen guns, cane guns, and smooth-bore pistols chambered for shotgun shells are common examples.
Not Every Large-Bore Firearm Is a Destructive Device
The ATF can exempt shotguns and shotgun shells recognized as particularly suitable for sporting purposes, and large-bore rifles intended solely for sporting use can also fall outside the definition.4eCFR. 27 CFR Part 479 – Machine Guns, Destructive Devices, and Certain Other Firearms Antique devices redesigned for signaling, pyrotechnic, or safety purposes are excluded too.
Machine Guns Are a Special Case
Of the six categories, machine guns are by far the most restricted. The Firearm Owners’ Protection Act, signed May 19, 1986, banned civilian possession of any machine gun not already lawfully owned before that date.5Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts No new machine guns can enter the civilian market. That fixed supply drives prices for transferable pre-1986 machine guns from around $8,000 for basic models to more than $50,000 for desirable examples. Government agencies and licensed manufacturers with special demo permissions can still acquire post-1986 machine guns; ordinary buyers cannot.
The other five categories have no equivalent freeze. New suppressors, SBRs, SBSs, AOWs, and destructive devices can be manufactured, sold, and transferred to eligible civilians through the standard NFA process.
How Someone Legally Owns One
Every NFA transfer requires ATF approval before the buyer takes possession.6Office of the Law Revision Counsel. 26 USC 5812 – Transfers The buyer selects the item at a licensed dealer, and the dealer holds it while the paperwork clears. The buyer submits ATF Form 4 with fingerprints and a passport-style photograph, and sends a copy of the completed form to the chief law enforcement officer in their jurisdiction as a notification (not a request for permission).7Bureau of Alcohol, Tobacco, Firearms and Explosives. ATF Form 5320.4 (Form 4) – Application to Transfer and Register NFA Firearm
The ATF runs a federal background check. If the transfer would put the buyer in violation of any law, federal or state, the application is denied. Someone building an NFA firearm rather than buying one uses ATF Form 1, with the same fingerprint, photo, and CLEO notification requirements.8Bureau of Alcohol, Tobacco, Firearms and Explosives. Firearms Forms Electronic filings clear faster than paper: as of January 2026, the average processing time for an electronic Form 4 is about 10 days for individual applicants and 11 days for trust applicants.9Bureau of Alcohol, Tobacco, Firearms and Explosives. Current Processing Times
Possessing an NFA item that isn’t registered to you in the National Firearms Registration and Transfer Record is a federal felony. The maximum penalty for any NFA violation is 10 years in federal prison and a fine of up to $250,000 for an individual, plus seizure and forfeiture of the firearm.10Office of the Law Revision Counsel. 26 USC 5871 – Penalties
The 2026 Tax Change
For decades, every NFA transfer carried a $200 federal transfer tax, reduced to $5 for AOWs. As of January 1, 2026, that tax dropped to $0 for suppressors, short-barreled rifles, short-barreled shotguns, and AOWs. Machine guns and destructive devices still carry the $200 transfer tax.11Office of the Law Revision Counsel. 26 USC 5811 – Transfer Tax Registration and background check requirements did not change. The paperwork is the same; it just costs less to file for most categories.
State Law Still Applies
Federal approval does not override state law. Suppressors are currently illegal for civilians in California, Delaware, Hawaii, Illinois, Massachusetts, New Jersey, New York, and Rhode Island. Machine gun rules vary separately: some states permit pre-1986 transferable machine guns, others ban them outright. SBR and SBS rules also differ by state. An ATF-approved Form 4 will not protect you from state prosecution, so anyone considering an NFA purchase should confirm their state allows that specific category before starting the federal process.