Tech Spec: V20N3

By Rick Vasquez

Silencers have been regulated since the enactment of the National Firearms Act (NFA) of 1934. The NFA is under Title 26 of the United States Code, which is the tax code. In an effort to curb violence by organized crime hierarchies and celebrated criminals, congress wanted to regulate certain firearms with the passage of the NFA. The population at the time would not accept gun control, so to get around this congress passed a “making” or transfer tax of $200.00 on firearms that would be enumerated in the NFA.

Statutes and regulation regarding silencers

Until 1968 the only firearms regulations were the regulations in the NFA. In 1968, with the enactment of the Gun Control Act (GCA), firearms would now also be regulated by the criminal code and a silencer would be identified as a firearm. The GCA is Title 18 of the United States Code and this is part of the criminal code. Unlawful use of a firearm or possession of a silencer by a prohibited person would now also be a violation of the criminal code. As we previously stated the NFA is a tax code. Though there is a significant penalty to violate the NFA, Title 18 has more robust penalties for violations.

Prior to 1986 a silencer was simply defined as “a muffler or a silencer for any kind of gun whether or not such a gun is included within the definition of firearm in the bill”. The silencer definition remained unchanged until the passage of the Firearms Owners Protection Act in 1986 (FOPA). The definitions of silencer would now also include all of the separate components of a silencer. Definition of a firearm in in Title 26 enacted in 1934:

Since 1934 treasury regulations of the NFA, 26 C.F.R. §179.11 also defines silencer as “Muffler or Silencer. Any device for diminishing the report of a portable weapon such as rifle, carbine, pistol, revolver, machine gun, submachinegun, shotguns, fowling piece, or other device from which a shot, bullet, or projectile may be discharged by an explosive, and is not limited to mufflers or silencers for “firearms” as defined.”

Definition of a silencer in 1968:
Title 18, U.S.C., §921. Definitions” (a) As used
in this chapter—
“ (3) The term ‘firearm’ means (A) any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive; (B) the frame or receiver of any such weapon; (C) any firearm muffler or firearm silencer; or (see PUBLIC LAW 90-618-OCT. 22, 1968)

With the passage of the FOPA the definition of silencer was expanded to include all of the components of a silencer. The GCA was amended with section 921 (a)(24) The terms “firearm silencer” and “firearm muffler” mean any device for silencing, muffling, or diminishing the report of a portable firearm, including any combination of parts, designed or redesigned, and intended for use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication”.

There are multiple reasons of why the definition of a silencer was expanded. One of the prevailing factors was that because components of a silencer were not specifically called out in the regulations, components could and were being sold without any regulations. At many gun shows of the time a person could purchase all of the internal components of a silencer at one table and tubes/bodies at other tables, and be in possession of an unregistered silencer. Then this person (if desired) could Form the group of components as a complete silencer. Or the components could be assembled and enter the illegal gun market as an unregistered silencer.

Silencer components regulated

The definition of a silencer had now become very broad and has led to a variety of interpretations from ATF. There is confusion on what is classified as a silencer, how components of a silencer are defined, and how to make and register silencers; both by manufacturers and by individuals. To compound this confusion there have been opinion changes by ATF, there are different responses given by ATF personnel in the field, and there are arbitrary and incorrect instruction by ATF field personnel given to manufacturers of silencers.

For clarification each component of the definition will be explained.

If a component has only one use, which is to assemble or fabricate a silencer, that component would be regulated as a silencer. This portion of the definition led to a comical exchange with ATF on Chore Boy wire scrubbing pads and a silencer manufacturer (left unnamed). If a person purchases Chore Boy scrubbing pads at Home Depot they and Home Depot are not in violation of the NFA. If a person purchases 6 feet of 2” metal tube they are not in possession of silencer tubes (though I have heard a person in ATF say they were). However, if I take those scrubbing pads and roll them up to fit into a section of the metal tube, cut the metal tube into sections, and it can be proven the intent is to make components of a silencer then all of the rolls of wire and sections of the 6 foot tube could be defined as silencer components.

When weapons manufacturer SWD developed a conical threaded device for the purpose of accepting a soda bottle to act as a silencer the device itself was classified as a silencer. Because at the time this design was developed the opinion of ATF was anything that could muffle or diminish the report of a portable firearm, was attached to the muzzle of a firearm, it would be a silencer. The new goal of the manufacturer is to design an object that can operate in two different capacities. If your muzzle attachment can have two functions then it has a possibility of not being classified as a silencer. For example silencer companies are marketing muzzle brakes that have the same physical appearance of silencer baffle as a muzzle brake. (These have been submitted to ATF and have received a positive determination). If this muzzle device is later covered with a tube it will work as a baffle and need to be registered as a silencer. Since ATF has determined it has a dual use when used as a muzzle brake it is not a silencer.

Additionally, in recent times ATF has used “intent and “any part intended only for use in such assembly or fabrication” to make different classifications. If a soda bottle is attached to a firearm and is called a “solvent catcher”, ATF has held that this use of a soda bottle is not a silencer. Therefore, soda bottles and oil filters attached to muzzles and used as “solvent catchers” are no longer classified as silencers unless they are shot through (see ATF letter on solvent traps Kadiz Gun works). This has led to a plethora of muzzle attachments that can be used to attach oil filters, flashlight bodies, and any type of bottle imaginable being sold on the internet. If this muzzle attachment were fired through then it would be considered a silencer.

Making versus manufacturing of silencers

Under the GCA a person that is not prohibited from owning a firearm can make any firearm for personal use including firearms under the NFA. However, any firearm regulated by the NFA must be registered prior to being made, The NFA regulates the making or manufacturing of a specific group of firearms by tax registration. A maker and a manufacturer are separate categories under the NFA. A non-prohibited person can make NFA firearms for personal use without a manufacturer’s license, if that person follows the guidelines prescribed by the NFA.

“Title 26, U.S.C., § 5822 Making

No person shall make a firearm unless he has (a) filed with the Secretary a written application, in duplicate, to make and register the firearm on the Form prescribed by the Secretary; (b) paid any tax payable on the making and such payment is evidenced by the proper stamp affixed to the original application Form; (c) identified the firearm to be made in the application Form in such manner as the Secretary may by regulations prescribe; (d) identified himself in the application Form in such manner as the Secretary may by regulations prescribe, except that, if such person is an individual, the identification must include his fingerprints and his photograph; and (e) obtained the approval of the Secretary to make and register the firearm and the application Form shows such approval. Applications shall be denied if the making or possession of the firearm would place the person making in violation of law.”

An individual is considered a “maker” when making an NFA regulated firearm. When making a personal firearm under the GCA, markings are not required to be placed on firearms. All firearms made or manufactured under the NFA, whether by an individual or a manufacturer, are required to be marked in accordance with Title 26, U.S.C., § 5842 Identification of Firearms and 27 CFR, § 479.102 How must firearms be identified.

Once you have applied on a Form 1 to make and register a silencer and received your approval you have the authority to make all of the components for one silencer. Though all components of a silencer are regulated, as a maker making one silencer, the serial number and marks of identification need only go on the completed silencer. As a note, if you are making the firearm under a trust the complete name of the trust must be used when marking your firearm. Since a trust is a legal name it cannot be abbreviated. When the silencer is complete, ensure all excess components are destroyed. Excess components would require marking.

Licensed manufacturers of NFA firearm have a much clearer path in the regulations. Once a person or entity is a licensed manufacturer under the NFA they may began making NFA firearms. Manufacturers can make silencer components and stockpile these components without recordkeeping, as long as they are not assembled into a complete silencer. Components of silencers do not have to be recorded on a Form 2 while stockpiled and are not required to be marked and transferred on a Form 3 when shipped to another NFA manufacturer. If you ship silencer components to another manufacturer, ensure you are not transferring a complete silencer in an unassembled state. When shipping a complete silencer you must record it on a Form 2 and transfer it on a Form 3, 4, or 5 depending on the end user.
Unfinished components

As with firearms manufacturers subcontracting work on firearms receivers, manufacturers of silencers attempt to subcontract work to machine shops with equipment in place. The issue is: when does a piece of metal become a silencer? Because of this portion of the definition “and any part intended only for use in such assembly or fabrication,” a person must be cautious when making components. When investing into this type of practice you must verify with ATF whether the item you are making has reached a stage of manufacturing in which ATF would call it a silencer.


The owning, making, or manufacturing of silencers is regulated but not prohibited. Ensure you follow all prescribed regulations and statutes governing silencers.

Silencer terms from ATF and Association of Firearms and Tool Mark Examiners

Absorbent: Material used to slow and cool gases emitted during the discharge of a firearm, thus dampening sound.
ANSI Standard: Type of sound field standard used when measuring sound in a diffuse field.
Back Baffles: A type of baffling system in which disclike baffles permit gases to escape both backwards and forwards from an expansion chamber.
Baffles: Components of a silencer, usually discs, washers, wafers, etc., which slow the flow of gas by allowing it to expand within small compartments: See BAFFLING SYSTEM.
Baffle Spacers: See SPACERS.
Baffling System: Series of baffles designed to restrict the passage of gas generated during the discharge of a firearm. Can be made of metal, rubber, cork, leather, plastic, etc. and can be conical, flat, or spiral in shape. See BAFFLES.
Ballistic Crack: See SONIC CRACK.
Barrel End Support: Structure which aligns the trajectory of the bullet in both the barrel of the gun and the silencer.
Bleed Holes: Holes drilled in the barrel of a firearm which permit gases to escape into a silencer, thereby decreasing ballistic pressure and reducing the velocity of a bullet to a subsonic speed. Also called GAS PORTS, PORTING, PORT HOLES.
Bleeding: Escape of gases through bleed holes. See BLEED HOLES.
Blowby: Leakage of gas around a bullet fired through the baffles in a silencer which is generated by the difference in diameter between the bullet and holes in the baffles, thus permitting the gas to precede the bullet out of the silencer.
DeciBel: Logarithmic unit equivalent to 1/10 of a Bel which describes the amount of change in sound intensity, power, or current. Abbreviated dB.
DeciBel Meter: Calibrated instrument used to measure sound pressure level in deciBels.
End Cap: Sealed distal portion of a silencer through which the bullet and escaping gases pass.
Entrance Chamber: In some silencers, a first chamber which may contain absorbent materials.
Exit Chamber: In some silencers, a last chamber leading to an endcap which blocks and deflects blow-by gases.
Expansion Chamber: Space within a silencer which allows escaping gases to slow, diffuse and cool.
First Round Flash: Muzzle flash generated by secondary burning of residue gases and propellants due to oxygen present in a silencer when the first shot is fired.
Free Field: Environment in which sound does not reflect from any surface, but is emitted equally in all directions.
Gas Ports: See BLEED HOLES.
IEC Standard: Type of sound field standard used when measuring free fields of sound. See FREE FIELD.
Jet Noise: Sound created within a silencer by the turbulence of escaping gases.
Kfactor In some sound meters, a correction factor which is added to all measured values.
Leq: When measuring sound levels, the average sound pressure level produced during the period of measurement.
MAC: Acronym for Military Armament Corporation, one of the original producers of modern silencers.
Mechanical Noise: Noise produced by mechanical movements within a gun, such as trigger pull and hammer drop, to fire a round. Also called ACTION.
Microphone: Electroacoustic transducer which converts the energy in sound waves to electrical energy which can be more easily displayed and analyzed, as by an oscilloscope. Also see TRANSDUCER, OSCILLOSCOPE.
Muffler: See SILENCER.
Muzzle Blast: Noise occurring during the discharge of a firearm as a result of the rapid expansion of gases leaving the muzzle.
Oscilloscope: Electronic instrument utilizing cathode ray tubes to produce a waveForm display showing the relationship between time and the amount of sound produced or between two other variables.
Outer Tubing: See SILENCING TUBE.
Port Holes: See BLEED HOLES.
Porting: See BLEED HOLES.
Primer Initiation: Sound produced by the leakage of some propellant gases backwards Pulse around the cartridge case during the firing of a gun.
Report: Combination of sounds produced by the discharge of a firearm, including but not limited to mechanical noise, sonic crack; and muzzle blast.
SEL: Abbreviation for sound exposure level. See SOUND EXPOSURE LEVEL.
Silencer: Defined by the Federal Firearms Regulations Reference Guide 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 use in assembling or fabricating a firearm silencer or firearm muffler, and any part intended only for use in such assembly or fabrication. Also called SOUND MODERATOR, SOUND SUPPRESSOR, MUFFLER, SUPPRESSOR, NOISE SUPPRESSOR, MUZZLE SUPPRESSOR.
Silencer, Auxiliary: A silencer which can be removed from or attached to the muzzle of a firearm. Also called MUZZLE SILENCER. Contrast with INTEGRAL SILENCER.
Silencer, Barrel: A silencer which surrounds the barrel of a weapon.
Silencer, Disposable: A silencer which decreases in effectiveness after each use and must be cleaned or replaced frequently.
Silencer, Eccentric: A silencer in which the trajectory of the bullet is offset from the center of the silencer so as to permit use of the original sights on the firearm. Also called OFFSET SILENCER.
Silencer, Homemade: A silencer fashioned from readily obtainable materials; an improvised silencer.
Silencer, Integral: A silencer which is a component part of a firearm and is carried while attached to the gun. Contrast with AUXILIARY SILENCER.
Silencer, Internal: A silencer housed inside the barrel of a weapon which is fired using subcaliber ammunition. Also called INTERNAL BARREL SILENCER.
Silencer, Internal: See SILENCER, INTERNAL. Barrel
Silencer, Muzzle: See SILENCER, AUXILIARY.
Silencer, Offset: See SILENCER, ECCENTRIC.
Silencing Tube: Portion of a silencer which encapsulates all components of the silencing unit and which contains and controls the expansion of escaping gases. Also called HOUSING, OUTER TUBING.
Sonic Boom: See SONIC CRACK.
Sonic Crack: Sound made by the shock waves of a bullet traveling faster than the speed of sound. Also called BALLISTIC CRACK, SONIC BOOM.
Sound Exposure Level: Abbreviated SEL. When measuring sound, a level which, when maintained for a one second interval, is equivalent to the total acoustic energy generated by the measured noise.
Sound Moderator: See SILENCER.
Sound Pressure Level: Measure of variation in atmospheric pressure resulting in a sound to level which the ear responds. Measured by a sound level meter in decibels.
Spacers: Used to separate the baffles in a silencer in order to trap expanding gases. Also called BAFFLE SPACERS.
SPL: Acronym for Sound Pressure Level.
Subsonic: Traveling more slowly than the speed of sound (< 1100 fps).
Suppressor: A type of silencer which reduces muzzle blast by decreasing the velocity of escaping gases but maintains a bullet’s high velocity. Also called MUZZLE SUPPRESSOR, NOISE SUPPRESSOR, SOUND SUPPRESSOR. See also SILENCER, MUZZLE BLAST.
Suppressor, Baffle: Suppressor containing metal baffles which typically does not mark the bullet fired through it. Does not produce forensic evidence on the bullet which would allow determination of the type of silencer used. Contrast with W1PE SUPPRESSOR.
Suppressor, Noise: See SILENCER, SUPPRESSOR.
Suppressor, Sound: See SILENCER, SUPPRESSOR.
Suppressor, Wipe: Suppressor containing discs with holes smaller in diameter than the bullet passing through them. Results in markings on the bullet which can be utilized in forensic examination to determine the type of silencer used but may deForm original markings produced by the passage of the bullet down the gun barrel. Contrast with BAFFLE SUPPRESSOR.
Threaded Collar: Region of an auxiliary silencer used for attachment to the muzzle of a firearm.
Transducer: Device, such as a microphone, which transForms energy from one Form to another. See MICROPHONE.

This article first appeared in Small Arms Review V20N3 (April 2016)
and was posted online on February 19, 2016


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