Undetectable Firearms Act

Disclaimer: This is educational information only, not legal advice. Always consult with a qualified attorney for legal guidance.

Why it matters: The Undetectable Firearms Act of 1988 (18 USC § 922(p)) makes it a federal crime to manufacture, import, sell, ship, deliver, possess, transfer, or receive any firearm that can't be spotted by standard security equipment—and with 3D printing tech getting cheaper every year, this 36-year-old law is more relevant than ever.

Congress passed this back when Glocks first hit our shores and politicians freaked out about "plastic guns." Never mind that every Glock has a steel barrel, slide, springs, and enough metal parts to light up a metal detector like a Christmas tree.

The legal reality: Every firearm must contain enough metal to trigger both metal detectors AND show up on X-ray machines used in security screening. This isn't just about airport security—we're talking courthouses, government buildings, anywhere they've got metal detectors and X-ray gear running.

The detection standard has two parts that both have to be met:

Metal detector visibility: Must trigger standard walk-through detectors
X-ray visibility: Must show up clearly on screening equipment

Between the lines: This law was pure panic legislation in response to Glock hysteria, but it actually makes sense from a security standpoint. The politicians who wrote it probably couldn't tell a Glock from a garden hose, but they accidentally created something reasonable.

Modern 3D printing has given this old law new teeth. You can print receiver components, grip frames, even simple single-shot designs entirely in plastic. But here's the thing—even a basic functional firearm needs metal parts to actually work reliably.

What You Need to Know

What this means for you: If you're buying commercial guns or standard home builds, you're fine. Your polymer-framed Glock, Springfield XD, or any other factory gun has plenty of metal. This law bites people trying to make deliberately undetectable weapons or those who don't understand what "detectable" actually means.

The law covers every step of the process:

Manufacturing: Building one yourself counts
Importing: Bringing one in from overseas
Selling/transferring: Passing it to someone else
Possessing: Just having one in your safe

The bottom line: Don't try to make guns that dodge metal detectors. It's stupid, it's illegal, and honestly, it's unnecessary—legal firearms work better anyway.

How This Plays Out in Reality

Congress keeps renewing this thing because nobody wants to be the politician who voted to allow undetectable guns. Most recent renewal was 2024, and it'll probably get renewed again when it comes up.

What they're saying: The exceptions are narrow and don't apply to regular folks:

Government agencies: Military and law enforcement with official need
Authorized contractors: Companies working directly with government
Maintenance situations: Temporarily removing parts for cleaning doesn't count

The law applies to complete, functional firearms—not individual parts. You can legally own plastic components, but assembling them into a working gun that fails the detection test crosses the line.

By the numbers: Violations carry serious federal penalties. We're talking potential prison time, not a slap on the wrist. The feds don't mess around with firearms violations, especially ones involving security concerns.

Common Sense Guidance

Most shooters never have to think about this law. Your carry gun, hunting rifle, or home defense shotgun all have enough metal to meet requirements easily. Even if you're building AR-15s or 1911s at home, you're using standard metal parts that exceed the detection threshold.

If you're getting into manufacturing or experimenting with alternative materials, think carefully. Adding a tiny piece of metal to an otherwise plastic gun probably won't cut it—the detection requirement is about reliable identification by security equipment, not just technically containing some metal.

What this means for you: When in doubt, stick with proven designs using traditional materials. The cutting edge is a great place to cut yourself legally.

Busting the Myths

People get confused about this law because it touches on both technical and legal issues. Here's what's actually true:

"Glocks are illegal plastic guns": Wrong. Every polymer-framed pistol has a steel barrel, slide, and plenty of other metal parts
"This only applies to 3D printed guns": Nope. Any undetectable firearm violates the law, regardless of how it's made
"Add any metal piece and you're legal": False. The metal content has to be enough for reliable detection
"Home builds are exempt": Not even close. The law covers all firearms, period
"Just the frame needs metal": Wrong again. The complete functional firearm must meet detection standards

The Real World Impact

For 99% of gun owners, this law is invisible. You buy factory guns or build standard designs with normal parts, and you're automatically compliant. The law mainly catches people who are either deliberately trying to evade security or who misunderstood what's required.

The rise of 3D printing has definitely put this law back in the spotlight. You can print some pretty sophisticated firearms components now, but trying to make a completely undetectable gun is both illegal and impractical. Even basic functionality requires metal springs, firing pins, and usually barrels.

The bottom line: Stick to standard designs and materials, and this law will never affect you. Start experimenting with minimal-metal designs, and you're potentially looking at federal charges.

This information is provided for educational purposes only and does not constitute legal advice. Gun laws are complex and change frequently. Always consult with a qualified attorney for legal guidance specific to your situation.

Last Updated: 2026-01-15

Join the Discussion

How do you think the current Undetectable Firearms Act holds up against newer polymer frames and 3D printing tech—does it actually address what lawmakers are concerned about, or is it already outdated?

Undetectable Firearms Act

Quick Reply