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ATF Issues Open Letter on “Solvent Trap” Silencers

The move continues the agency’s efforts to crack down on retailers selling silencer-building kits online

The Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) has published an open letter to Federal Firearms Licensees (FFLs) reiterating that the DIY silencer-building kits sold and marketed online as “solvent traps” are considered silencers in accordance with federal law, meaning they are subject to the registration and background check requirements of the National Firearms Act (NFA).

To learn more about silencers and the “solvent trap” kits sold online to skirt NFA regulations, click here.

Federal regulations define silencers as “any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for the use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication” (emphasis added).

According to the ATF, “Some of the devices commonly marketed as solvent traps have been determined to meet the definition of ‘firearm silencer’ because they have the objective design features and characteristics indicating that the device is ‘for’ reducing the report of a portable firearm.” Those “features” include “holes (or marks indicating where holes should be drilled) that allow the passage of a projectile” as well as sound-dampening chambers known as “baffles.”

The ATF notes that “[w]hile increasing the effectiveness of a firearm silencer, these same objective design features offer no advantages in collecting or filtering cleaning solvent.” The letter also includes this image:

An ATF diagram of a "solvent trap" silencer with sound-dampening baffles, shown assembled and disassembled.

In recent years, the ATF has shut down several companies — such as Darkside Defense and Diversified Machine — attempting to sell “solvent traps” that included all of the parts required to operate as silencers online. The new open letter continues the agency’s enforcement efforts while bolstering transparency.

As the ATF states, “Over the years, many companies involved in marketing such ‘solvent traps’ have asserted that they are permitted to manufacture, transfer, or import these items because they are not yet ‘complete’ and therefore do not qualify as ‘firearm silencers’ under Federal law. However, this assertion is incorrect because a component of a ‘firearm silencer’ need not be fully functional before it is recognized as a ‘part intended only for use’ in assembling or fabricating a ‘firearm silencer.’”

Finally, the letter makes it clear that individuals cannot purchase one of these kits and then attempt to register the silencer with the ATF. “An NFA firearm that has already been made/manufactured in violation of the NFA may not be registered by the current possessor.”

The news comes as the gun industry celebrates the introduction of the Tax Stamp Revenue Transfer for Wildlife and Recreation Act, which, if enacted, would require the ATF to process silencer approvals in 90 days or less while redirecting tax stamp revenue from the Treasury to the Pittman-Robertson Wildlife Conservation Act, which funds wildlife conservation, hunter education, and shooting range programs.

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