Congress·In Committee·H.R. 4221

Gun Safety: Updates to the Ban on Undetectable Firearms

Undetectable Firearms Modernization Act

Legislative Progress

House

Senate

President

Law

This bill updates a 1988 law to ensure that modern firearms, like those made with 3D printers, can’t sneak through security. It requires every gun to have a major component—like the frame or barrel—that shows up clearly on airport X-ray machines and metal detectors.
To make the rules clearer, the bill defines "detectable" as having the same magnetic strength as 3.7 ounces of stainless steel. This prevents people from making plastic guns that are invisible to standard security equipment used at airports and government buildings.
The new rules would also apply to prototypes, which are early test versions of guns. This ensures that designers cannot claim a plastic gun is just a test model to avoid following the law.
Guns made specifically for the U.S. military or federal law enforcement are exempt from these rules. This allows the government to continue using specialized equipment for national security purposes.

2 milestones2 actions

Jun 27, 2025House

Referred to the House Committee on the Judiciary.

Jun 27, 2025

Introduced in House

Document Type

Congressional Bill

Official Title

Undetectable Firearms Modernization Act

Bill NumberHR 4221

Congress119th Congress

ChamberHouse of Representatives

Latest ActionReferred to the House Committee on the Judiciary.

Congress.gov

Official legislative information

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