An oil filter suppressor, also known as an “improvised suppressor,” is a makeshift device designed to reduce the noise of a gunshot. Typically, these devices are made from a car oil filter attached to the muzzle of a firearm using an oil filter muzzle adapter. While oil filters were not designed for this purpose, their construction can provide some sound dampening when used in this way.
In the United States, the use and possession of an oil filter suppressor is considered illegal unless it is registered with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) as a legitimate suppressor. Under the National Firearms Act (NFA), firearm suppressors are considered Title II weapons, meaning they are subject to federal regulation, taxation, and registration.
The penalties for possessing an unregistered oil filter suppressor can be severe. Individuals found guilty can face up to 10 years in prison, a fine of up to $250,000, or both. Additionally, the firearm and any other related items could be confiscated.