Any Other Weapon (AOW): Registration, Ownership, and Penalties

Under the National Firearms Act, an “Any Other Weapon” (AOW) is a catch-all category for concealable firearms that fire a projectile but don’t fit the NFA’s definitions of a pistol, revolver, rifle, shotgun, short-barreled rifle, short-barreled shotgun, or machinegun. Disguised firearms like pen and cane guns, smooth-bore pistols, certain combination guns, and handguns modified with a vertical foregrip all fall here. To possess one legally you need ATF registration, a background check, fingerprints, a photo, and CLEO notification. The federal transfer and making tax for an AOW is currently $0, but the paperwork and the criminal exposure for skipping it are the same as for any other NFA firearm.¹

What Qualifies as an Any Other Weapon

The statutory definition sits in 26 U.S.C. § 5845(e). The unifying thread across the category is that these are concealable weapons capable of firing a shot through an explosive charge but aren’t standard handguns, rifles, or shotguns.²

Disguised Firearms

Pen guns, cane guns, wallet guns, and cellphone guns are the classic AOWs. The defining feature is that the device can discharge a shot while still appearing to be an ordinary object. Caliber and power don’t matter; the disguise plus the ability to fire is what puts it in the category.²

Smooth-Bore Pistols

A pistol or revolver with a smooth bore designed to fire a fixed shotgun shell is an AOW. Rifle the bore and it becomes an ordinary handgun under federal law; leave it smooth and you’re in NFA territory. Firearms like the H&R Handy Gun were originally manufactured in a pistol configuration and were never designed to be fired from the shoulder, so they don’t meet the statutory definition of a shotgun, which is why they land here instead.³

Combination Guns

A less common subcategory covers weapons with combination shotgun and rifle barrels between 12 and 18 inches long that can fire only a single shot from either barrel before manual reloading. The Marble’s Game Getter is the canonical example. Because these were originally built in that configuration rather than cut down from a full-size shotgun, they don’t qualify as short-barreled shotguns.³

Handguns With a Vertical Foregrip

ATF has long held that attaching a vertical foregrip to a handgun turns it into an AOW, on the theory that the resulting firearm is no longer designed to be fired with one hand. Making the modification without first filing and receiving approval on Form 1 is a federal crime, and simply possessing the modified handgun without registration carries the same penalties. This is where owners get caught most often, because the change feels cosmetic.⁴

What the Category Excludes

Two exclusions matter. Pistols and revolvers with rifled bores are not AOWs, however concealable. And weapons designed, made, or intended to be fired from the shoulder that cannot fire fixed ammunition are excluded as well.²

Who Can Legally Own an AOW

You must be at least 21 to receive an AOW from a federal firearms licensee.⁵ You also cannot be a prohibited person under 18 U.S.C. § 922(g). That list includes anyone convicted of a crime punishable by more than one year of imprisonment, fugitives, unlawful users of controlled substances, people adjudicated as mentally defective or committed to a mental institution, those dishonorably discharged from the military, people under certain domestic violence restraining orders, and anyone convicted of misdemeanor domestic violence.⁶ Falling into any of these categories after registration puts you in violation immediately; there is no grace period.

Federal registration does not preempt state or local law. A few jurisdictions ban AOW possession outright, and others layer on their own permits or restrictions. Verify the law where you live before you buy, and check again before you travel with the firearm.

Registering an AOW: Form 4 vs Form 1

Which application you file depends on how you’re acquiring the firearm.

Buying an Existing AOW

Purchasing an already-registered AOW from a dealer or another individual goes through ATF Form 4, the Application to Transfer and Register a Firearm. The form captures your information along with the firearm’s serial number, caliber, barrel length, overall length, and manufacturer.⁷ The federal transfer tax for an AOW is currently $0.¹ You cannot take possession until ATF approves the transfer.

Making or Modifying Into an AOW

Building a new AOW or converting an existing firearm into one, such as by adding a vertical foregrip to a pistol, goes on ATF Form 1, the Application to Make and Register a Firearm. You have to receive approval before you make the modification.⁸ The making tax is also currently $0.⁹

What You Submit With Either Form

Two completed FBI FD-258 fingerprint cards per applicant (or per responsible person, if filing through a trust). Local law enforcement offices or private services generally charge $10 to $35.
A 2×2-inch passport-style photo taken within the past year.¹⁰
CLEO notification: a completed copy of the application sent to the chief law enforcement officer where you live, meaning your local chief of police, sheriff, head of state police, or district attorney. This is notice only. CLEO approval is not required.¹⁰

Applications can go in by mail with a check or money order for any tax due, or electronically through the ATF eForms portal with a credit card.¹¹ If you submit a Form 1 through eForms, paper fingerprint cards must be mailed within 10 days of the electronic filing, unless you upload a digital .EFT fingerprint file created by a live scan service. Digital fingerprints are valid for 12 months and process faster.¹⁰

As of early 2026, ATF reports average processing of roughly 10 to 36 days for eForms applications and 20 to 24 days for paper submissions, varying by form type and by whether you file as an individual or through a trust.¹² Approval comes back as a tax stamp confirming registration in the National Firearms Registration and Transfer Record. Keep a copy of the approved form accessible whenever you have the firearm with you.

Engraving Requirements if You Make the AOW

Form 1 makers are legally the manufacturer of the firearm and must permanently mark it before or upon completion. Required markings are your name (or the trust’s name), the city and state where the firearm was made, a unique serial number, the caliber, and a model designation if you assign one.¹³

The engraving must be at least .003 inches deep, measured from the flat metal surface rather than from any peaks, and the serial number must be in print no smaller than 1/16 inch.¹³ Serial numbers you assign yourself must include at least one numeric character; letters alone don’t satisfy the rule. Initials followed by four or more digits is a common approach.¹⁴ Compliant engraving typically runs $20 to $125.

Individual Registration vs an NFA Trust

The NFA defines “transfer” broadly enough to reach a temporary loan. If you register an AOW to yourself as an individual and let someone else possess it out of your presence, that can be an unlawful transfer even without money changing hands.¹⁵ Registering the firearm to a revocable trust or an LLC solves this: any trustee named in the trust document can lawfully possess and use it without the other trustees being present.

The tradeoff is paperwork. Under ATF’s Rule 41F, every “responsible person” in the trust, meaning the grantor, trustees, and any beneficiary with authority to direct trust management or handle its firearms, individually submits photographs, two FD-258 fingerprint cards, and ATF Form 5320.23 (the Responsible Person Questionnaire). Each responsible person goes through a separate background check and sends CLEO notification where they live.¹⁶ Naming a trustee who turns out to be a prohibited person can undermine the whole arrangement.

Attorney-drafted NFA trusts typically cost $300 to $2,500 depending on complexity and location. Online templates are cheaper but can create problems if they don’t line up with your state’s trust laws or NFA requirements.

Traveling With an AOW Across State Lines

AOWs have a real practical advantage over most other NFA firearms when it comes to interstate travel. Under 18 U.S.C. § 922(a)(4), prior ATF authorization on Form 5320.20 is required to transport a machinegun, destructive device, short-barreled rifle, or short-barreled shotgun across state lines. AOWs are not on that list, so no Form 5320.20 is required to take one out of state.¹⁷

The exemption only covers ATF’s advance permission. State and local firearms laws still apply everywhere you go, and a firearm that’s fully legal at home can be a felony across a state line.

Passing an AOW to an Heir

When a registered AOW owner dies, the firearm doesn’t automatically become legal for family members. The executor or administrator files ATF Form 5, the Application for Tax Exempt Transfer and Registration of Firearm, to transfer the AOW to a named beneficiary by bequest or intestate succession. The transfer is exempt from tax.¹⁸

The heir has to be legally eligible to possess firearms; a prohibited person cannot receive the transfer. If the estate wants to sell the AOW to someone other than a legal heir, that goes through the ordinary Form 4 process with whatever tax is in effect.

An NFA trust changes this picture. If the AOW is registered to the trust, the trust keeps owning it after the grantor’s death and successor trustees can possess the firearm right away without a Form 5, because the registered owner has not changed.

Penalties for Getting It Wrong

Making, possessing, or transferring an unregistered AOW is a federal felony. A conviction under 26 U.S.C. § 5871 carries a fine of up to $10,000, up to ten years in federal prison, or both.¹⁹ The same penalty applies to the person who bolts a vertical foregrip onto a pistol without filing Form 1 first, because the modification created an unregistered AOW.⁴

Firearms tied to knowing violations are also subject to seizure and forfeiture. Forfeiture proceedings must be initiated within 120 days of seizure, and seized firearms must be returned after acquittal or dismissal, unless returning them would itself place the owner in violation of the law.²⁰

1
Office of the Law Revision Counsel. 26 USC 5811 – Transfer Tax
2
Legal Information Institute. 26 USC 5845(e) – Any Other Weapon
3
Bureau of Alcohol, Tobacco, Firearms and Explosives. National Firearms Act Handbook
4
Bureau of Alcohol, Tobacco, Firearms and Explosives. Adding a Vertical Fore Grip to a Handgun
5
Bureau of Alcohol, Tobacco, Firearms and Explosives. Minimum Age for Gun Sales and Transfers
6
Bureau of Alcohol, Tobacco, Firearms and Explosives. Identify Prohibited Persons
7
Bureau of Alcohol, Tobacco, Firearms and Explosives. Application to Transfer and Register NFA Firearm (Tax-Paid)
8
Bureau of Alcohol, Tobacco, Firearms and Explosives. ATF Form 5320.1 – Application to Make and Register NFA Firearm
9
Office of the Law Revision Counsel. 26 USC 5821 – Making Tax
10
Bureau of Alcohol, Tobacco, Firearms and Explosives. NFA Form 1 Submission External Guidance with Q&A
11
Bureau of Alcohol, Tobacco, Firearms and Explosives. eForms Applications
12
Bureau of Alcohol, Tobacco, Firearms and Explosives. Current Processing Times
13
eCFR. 27 CFR 479.102 – Identification of Firearms
14
Bureau of Alcohol, Tobacco, Firearms and Explosives. NFA Handbook – Chapter 6 – Making NFA Firearms by Nonlicensee
15
Bureau of Alcohol, Tobacco, Firearms and Explosives. NFA Handbook
16
Bureau of Alcohol, Tobacco, Firearms and Explosives. Background Checks for Responsible Persons (Final Rule 41F)
17
Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts
18
Bureau of Alcohol, Tobacco, Firearms and Explosives. Application for Tax Exempt Transfer and Registration of Firearm (ATF Form 5)
19
Office of the Law Revision Counsel. 26 USC 5871 – Penalties
20
eCFR. 27 CFR 478.152 – Seizure and Forfeiture