Oil & Fuel Filter Suppressors / Silencers for Firearms

Suppressing the sound of a gunshot may be important in hostile and non-permissive environments. The sound of a gunshot can alert others to your presence and draw unwanted attention to your activities. When a gun is fired there are two major sounds. First is the explosion of the round itself being fired and gasses escaping from the barrel of the gun, and second is the sound of the bullet breaking the sound barrier (1,100 feet per second at sea level) if you are shooting supersonic ammunition. There is also the sound of the cycling of the firearm, but this noise is insignificant when compared to the sound of the shot itself.

To suppress the sound of a gunshot you need to resolve the two major sources of noise associated with the shot. We resolve the sound of the bullet breaking the sound barrier by using subsonic ammunition – that is bullets that travel slower than 1,100 feet per second. The problem of suppressing the sound of the round being fired is where suppressors / silencers come into play. In some countries you can buy a suppressor for your firearm with no more effort than buying the firearm itself (i.e. Norway and Poland). In other countries, the United States and the Czech Republic for example, suppressors are highly regulated and require additional applications and fees. If you are in a country that does not restrict the ownership of suppressors, or if you are able to obtain a permit to own a suppressor it is worth having one for any of your firearms where you can use subsonic ammunition.

While modern commercial suppressors can be somewhat complex in their design, suppressing the sound of a gunshot is not particularly difficult. It is interesting to note that a commonly available vehicle oil or fuel filter attached to the end of the barrel of a firearm will significantly reduce the sound of the gunshot. To use an oil or fuel filter as a suppressor you will need a threaded barrel on your firearm, an adapter with internal threads to match the barrel threads and external threads to match the oil / fuel filter threads. This is commonly ½-28 internal thread and ¾-16 external thread. These adapters are sold in many places for building solvent traps. Once you attach an oil or fuel filter to your firearm using this adapter you have a solvent trap, because one end of the filter remains closed. By drilling a hole in the end of the filter that lines up exactly with the barrel you have cleared a flight path for the bullet and created a basic sound suppressor.

More complex suppressors can be built from parts kits using Mag-Light flashlights as the suppressor tube (solvent trap tube), or from kits specifically designed to build suppressors (solvent traps), but as an expedient means the oil or fuel filter is quite effective.

“Hickok45” demonstrates an “Oil Filter Suppressor” on his YouTube channel.

A series on building suppressors from oil filters and fuel filters (currently banned on YouTube) is available on Full30.  And, part 3 of the series: Fuel Filter Silencer - What's Inside?