ATF Rules for
Rocketry Motors

The APCP Classification History

Ammonium Perchlorate Composite Propellant (APCP) — the propellant used in most E-motor and above commercial rockets — has had a complicated regulatory history with the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). In 2000, the ATF ruled that APCP met the statutory definition of a "low explosive" under the Safe Explosives Act, which would have required dealers to obtain explosives licenses and buyers to be licensed users — effectively making commercial HPR impractical for ordinary hobbyists.

The rocketry community, led by NAR and TRA, challenged this ruling aggressively. After years of litigation, the ATF and the courts ultimately determined that commercially manufactured, consumer-packaged APCP motors do not meet the definition of explosives when sold as assembled, end-use consumer products. The current regulatory position, confirmed through 2025, is that commercially manufactured APCP model rocket motors sold in their standard packaging as complete assemblies are not regulated as explosives under federal law for consumer purchase and use.

What IS Subject to ATF Oversight

While consumer APCP motor assemblies are exempt, several scenarios do bring ATF oversight into play:

Bulk Propellant

Loose APCP propellant — not assembled into a motor casing — is treated as a low explosive under federal law. Dealers who sell propellant reloads must maintain appropriate federal explosives licenses. The buyer of reloads does not typically need a license, but the dealer does. This is why you can buy reloadable motor systems at certified rocketry dealers but not at general sporting goods stores.

Large Single-Use Motor Quantities

Individual motors containing more than 62.5 grams of propellant in a single casing are treated as low explosives for dealer licensing purposes, even when sold as complete assemblies. This affects dealers more than buyers — dealers carrying these motors must hold appropriate ATF licenses — but buyers should understand that their dealer is operating under federal explosives licensing when they sell large HPR motors.

Experimental / Homemade Propellant

Any hobbyist who manufactures their own propellant — even for personal use — is engaged in explosives manufacturing under federal law and requires an ATF Low Explosives User Permit (LEUP). The LEUP process involves an application, background check, and inspection by an ATF Field Office. Both NAR and Tripoli have formal experimental programs that help members navigate this process, but the ATF permit is required regardless of organizational affiliation.

The Low Explosives User Permit (LEUP)

The LEUP is the federal permit required to manufacture low explosives (including APCP) for personal use in experimental rocketry. It is not a license to sell or transfer explosives — only to manufacture for your own use. Obtaining a LEUP involves:

1. Application to the ATF.

   Form ATF 5400.13/5400.16 (application for explosives license/permit). The application asks for personal information, intended use, storage arrangements, and organizational affiliation.

2. Background investigation.

   ATF conducts a background check. Federal disqualifiers (felony conviction, domestic violence misdemeanor, etc.) that apply to firearms also apply to explosives. Most hobbyists with clean records pass without issue.

3. Site inspection.

   An ATF Industry Operations Inspector may visit your premises to verify you have appropriate storage arrangements for explosives. This doesn't necessarily mean a magazine — for personal-use LEUP holders, a locked, secure storage location is often sufficient.

4. Organizational sponsorship.

   NAR and Tripoli both have formal programs to sponsor LEUP applicants and provide mentorship in safe propellant manufacturing. ATF expects LEUP holders to be affiliated with an established rocketry organization with an active safety program.

Transporting Motors

Transporting commercially packaged APCP motors in a private vehicle is generally legal without any special permit for quantities appropriate to personal use. Motors should be stored in their original sealed packaging, kept in a cool location (not in a hot trunk in summer), and separated from any ignition sources. Transporting large quantities of HPR motors across state lines is technically subject to DOT hazardous materials regulations for commercial shipments, but personal transport for hobby use within reasonable quantities is generally treated as consumer product transport by law enforcement.

Never ship APCP motors through USPS (prohibited). UPS and FedEx have specific dangerous goods shipping procedures for APCP — dealers use these procedures for mail-order motor shipments. Do not attempt to ship motors yourself without following carrier dangerous goods procedures.