Zip guns are illegal in almost every real-world situation. Federal law lets a private individual build a firearm for personal use without a license, but a typical zip gun, a smooth-bore pipe weapon, falls under the National Firearms Act and requires advance federal registration before construction. Build one without that paperwork and you commit a federal felony punishable by up to ten years in prison. If the weapon is made largely of plastic or other non-metallic material, it violates a separate federal law regardless of registration. State ghost gun statutes add another layer on top.
Why a Zip Gun Is an NFA Firearm
The National Firearms Act of 1934 regulates a specific list of weapons, and one of its categories, “any other weapon,” is where most zip guns land. Under 26 U.S.C. § 5845(e), an “any other weapon” includes any concealable weapon that fires a projectile using an explosive, and any pistol or revolver with a smooth bore.1Office of the Law Revision Counsel. 26 USC 5845 – Definitions
Zip guns are typically built from pipe or tubing, so the barrel has no rifling. That smooth bore is exactly what triggers the classification. A commercially made pistol with a rifled bore is explicitly excluded from this category. A homemade pipe gun is not. Once you build one without registering it, you possess an unregistered NFA firearm, and that alone is a felony.
The Gun Control Act does allow a private individual who is not “engaged in the business” of manufacturing to build a firearm for personal use without a Federal Firearms License, and federal law does not require that person to run a background check on themselves or engrave a serial number.2Bureau of Alcohol, Tobacco, Firearms and Explosives. Privately Made Firearms That permission does not override the NFA. It applies to ordinary rifled firearms built for personal use, not to smooth-bore pipe guns.
The Only Legal Path: Register Before You Build
If you want to lawfully make any NFA firearm, including a smooth-bore zip gun, you must complete the registration process before construction begins. Under 26 U.S.C. § 5822, no one may make an NFA firearm without first filing a written application, submitting fingerprints and a photograph, and receiving written approval from the ATF.3Office of the Law Revision Counsel. 26 USC 5822 – Making The ATF will deny the application if making or possessing the firearm would put the applicant in violation of any other law, including state law.
The application is ATF Form 1 (Form 5320.1), and it requires a background check through NICS.4Bureau of Alcohol, Tobacco, Firearms, and Explosives. Application to Make and Register NFA Firearm, ATF Form 5320.1 You must also submit a Responsible Person Questionnaire (ATF Form 5320.23) with fingerprint cards on Form FD-258.5Bureau of Alcohol, Tobacco, Firearms and Explosives. Firearms Forms The firearm cannot be built until approval comes back.
A common misconception is that registering an “any other weapon” costs $200 in tax. It does not. The $200 making tax under 26 U.S.C. § 5821 applies only to machine guns and destructive devices. For every other NFA firearm, the making tax is $0.6Office of the Law Revision Counsel. 26 USC 5821 – Making Tax The paperwork, fingerprints, background check, and wait are still required. There is no tax to pay.
Once approved, the finished firearm must carry identifying marks. Federal regulations require the serial number and maker’s name to be stamped or engraved to a minimum depth of .003 inches, with characters no smaller than 1/16 inch.7ATF eRegulations. 27 CFR 479.102 – Identification of Firearms
The Detectability Rule
Even a properly registered zip gun can be illegal if it fails the detectability test. Under 18 U.S.C. § 922(p), it is a federal crime to make, possess, sell, or transfer any firearm that cannot be detected by a walk-through metal detector calibrated to find a “Security Exemplar” containing 3.7 ounces of stainless steel shaped like a handgun. The law also prohibits any firearm whose major components, such as the barrel, slide, or frame, do not show up accurately on airport-style X-ray machines.8Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts
This matters because many zip guns are built from PVC pipe, wood, or 3D-printed plastic. A build that lacks enough embedded metal fails this test and is federally illegal even if every NFA requirement has been met. The Undetectable Firearms Act runs alongside the NFA, so a homemade weapon can violate both laws at once or either one alone. Knowingly violating this statute carries up to five years in federal prison.9Office of the Law Revision Counsel. 18 USC 924 – Penalties
People Who Cannot Make Any Firearm at All
Federal law bars entire categories of people from possessing or receiving any firearm, homemade included. The personal-use exception in the Gun Control Act does not override these prohibitions. Under 18 U.S.C. § 922(g), prohibited persons include:
- Anyone convicted of a crime punishable by more than one year in prison
- Fugitives from justice
- Anyone who unlawfully uses or is addicted to a controlled substance
- Anyone adjudicated mentally defective or committed to a mental institution
- People in the country illegally and, with limited exceptions, those on a nonimmigrant visa
- Anyone discharged from the military under dishonorable conditions
- Anyone convicted of a misdemeanor crime of domestic violence or subject to a qualifying protective order
If any of these apply to you, building a zip gun is a separate federal felony on top of whatever NFA or state charges apply.8Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts A prohibited person in possession of a firearm faces up to 15 years in prison with certain prior convictions.
State Laws Often Go Further
State law is where many people get caught off guard. Federal law does not require an individual to serialize a personally made firearm, but a growing number of states do. Some require anyone who builds a firearm to obtain a serial number from the state and engrave it on the weapon. Others require existing unserialized firearms to be reported to state authorities.2Bureau of Alcohol, Tobacco, Firearms and Explosives. Privately Made Firearms
The strictest states ban possession of unserialized firearms outright or prohibit 3D-printing firearms entirely. Some also ban distributing digital blueprints for 3D-printed guns. The specifics vary widely, and what is legal in one state can be a felony next door. These laws change often, so checking your state’s current statutes before building anything is not optional.
What Happens if You Get It Wrong
The federal consequences are severe, and multiple charges can stack.
- Possessing or making an unregistered NFA firearm is a felony punishable by up to 10 years in federal prison. The general federal fine cap for felonies is $250,000.10Office of the Law Revision Counsel. 18 USC 3571 – Sentence of Fine
- Knowingly violating the Undetectable Firearms Act carries up to 5 years in federal prison.
- A prohibited person in possession of any firearm faces up to 15 years with qualifying priors.
- State ghost gun and serialization violations can add prison time and fines, running concurrently or consecutively with any federal sentence.
A felony conviction for any of these offenses permanently strips your federal right to possess any firearm. That prohibition survives state-level restoration of civil rights in most cases.8Office of the Law Revision Counsel. 18 USC 922 – Unlawful Acts If an improperly built zip gun injures someone, the maker also faces civil liability, since the federal immunity protections that apply to licensed manufacturers do not extend to unlicensed individuals building homemade weapons.
Federal law leaves a narrow path to legally build a smooth-bore zip gun through NFA registration, a background check, and detectability compliance. Skipping any part of that path turns the finished weapon into a felony in your hands.