The short answer to this question that we get asked often is ... "It Depends." YES, you can modify your handgun or rifle, but it depends on what you want to do to it. The practical reality is that it comes down to two main types of modifications that a gun owner like you or I might want to do with our firearm. Specifically, most cosmetic functions such as paint scheme, engraving, or visual enhancement is generally ok while modifications such as adjusting the barrel length, changing the caliber, or installing enhancements such as a bumpstock or silencer are typically illegal without getting approval. This regulation stems from the 1934 National Firearms Act that was implemented as a response to the Valentine's Massacre in Chicago as an early effort to control the proliferation of high-powered firearms, including machine guns and other long guns that could be modified.
Owning a firearm is legal to some degree in every US state. But are you allowed to modify your firearm? This greatly depends on which state you live in and what type of modification you plan to make. To make sure that your gun modification is legal, here is a brief lowdown of some of the things you can and can’t do.
NOTE: As with anything that involves legal questions in such a rapidly changing area, if you are thinking about making modifications to a gun that you own, talk with your local gun store or contact a lawyer that is trained in firearms regulations. The ATF seems to constantly shift the definitions and regulations that they try to enforce and so what seems to be legal today might be illegal tomorrow.
Handguns vs Rifles, Shotguns and Other Long Guns
Taken from the ATF.gov website:
"One version of the Marble’s Game Getter was produced with 18-inch barrels and a folding shoulder stock. This model of the Game Getter, as manufactured, is not subject to the provisions of the NFA because it has barrels that are 18 inches in length and the overall length of the firearm, with stock extended, is more than 26 inches. However, if the shoulder stock has been removed from the 18-inch barrel version of the Game Getter, the firearm has an overall length of less than 26 inches and is an NFA weapon. Specifically, the firearm is classified as a weapon made from a rifle/shotgun."
The "any other weapon" (AOW) category under the National Firearms Act (NFA) generally excludes weapons intended to be fired from the shoulder that cannot fire fixed ammunition, and pistols or revolvers with a rifled bore. However, altering a pistol or revolver by adding a second vertical handgrip transforms it into an AOW because this modification means the weapon is no longer designed to be fired with just one hand, bringing it under NFA regulation. Notably, pistols and revolvers with rifled bores aren't classified as AOWs if they remain unmodified in this manner.
Conversely, any pistol or revolver with a barrel that lacks a rifled bore, regardless of other characteristics, is considered an AOW and subject to NFA rules.
Confused yet? Yeah ... a lot of law abiding gun owners are too and probably the folks in congress who are creating our gun laws are too but few folks are willing to apply some basic common sense and make the laws easier to understand and allow more flexibility in terms of what you or I can do with firearms that we legally own.
A Quick Look At Legal and Illegal Gun Modifications
As mentioned above, these guidelines generally only apply to guns that are covered under the NFA and those are limited to firearms designed to be used with two hands. However, before modifying a handgun you should confirm that your concept will not get you in trouble.
| Category | Modification | Description | Legal Considerations |
|---|---|---|---|
| Legal Gun Modifications | Cosmetics and Ergonomics | Altering the look and feel of the firearm with new sights or grips. | Generally legal; designed to personalize the firearm to the owner's preferences. |
| Caliber Conversion | Changing the barrel or converting the chamber to accept a different caliber for improved performance. | May be a DIY job or require a gunsmith, depending on the firearm. Legal, but check specific regulations. | |
| Accurizing | Making adjustments to improve firearm accuracy, such as installing an improved trigger kit or recrowning the barrel. | Legal; involves enhancing the firearm's performance. Some modifications might require NFA approval and a fee (e.g., adding a suppressor). | |
| Illegal Gun Modifications | Shortening Shotguns | Reducing a shotgun's barrel to under 18 inches or its overall length to under 26 inches. | Illegal federally and likely to be illegal in all states. |
| Shortening Rifles | Cutting a rifle barrel under 16 inches or its overall length under 26 inches. | Illegal federally and likely to be illegal in all states. | |
| Converting Semi-Automatic to Automatic | Converting a semi-automatic rifle to a fully automatic firearm. | Illegal under federal law, and likely to be illegal under state laws. | |
| Installing Bump Stocks | Installing devices that increase the firing rate of semi-automatic guns by using the gun's recoil to fire more rapidly. | Illegal under federal law as of the most recent updates; many states also ban or restrict these modifications. |
Please note: Gun laws vary significantly by location, and while a modification may be legal at the federal level, it could be illegal in certain states or localities. Always confirm the legality of any modification in your specific location before proceeding.
What modifications are legal?
You are generally allowed to make aesthetic and ergonomic upgrades. This includes changing the color or adding a pattern to your gun, or adding a new sight or a stabilizing arm to improve comfort and accuracy. Adding features like straps is totally legal too.
Various barrel upgrades are widely legal such as recrowning the barrel for greater accuracy or changing it completely to fire a new caliber. It is safest to hire a gunsmith to do this, although some states allow you to do it at home.
What modifications are illegal?
Certain conversions are illegal in certain states. For example, fitting a silencer to a gun is illegal in the likes of New York and Illinois. So it’s important to look up your individual state’s laws.
What about modifications that are illegal across the country? Certain barrel modifications fall under this category such as reducing a shotgun’s barrel to under 18 inches or a rifle’s barrel to under 16 inches. You also cannot install a bump stock since 2018. Neither can you turn a semi-automatic gun into a fully automatic gun. There are however still legal ways to increase the rate of fire such as this Glock binary trigger.
You also cannot remove the serial number on a firearm. These are used to identify legally registered firearms and your gun could be confiscated if it does not have a serial number. Home-made guns do not need these, but you do still need to get them legally approved as mentioned earlier.
As for cosmetic upgrades, it is illegal to make a working firearm look like a toy. Similarly, a gun cannot be made to look like a replica, although it is largely up to a jury as to what may classify as this.
Conclusion
Modifying a gun is legal, but within reason. Most cosmetic upgrades are allowed except for making a gun look like a toy or a replica, and most ergonomic upgrades are fine. And while you can recrown or replace the barrel, you must avoid shortening it beyond the regulated length or adding a silencer if you live in a state where these devices are banned. You should also avoid turning semi-automatic guns into fully automatic guns. To be safe, always check with your state and local laws before modifying a gun based on the guidelines outlined by the federal NFA. Even better, look for a gunsmith who can work with you to make the modifications that you are dreaming of.
