The Complete NFA and Suppressor Glossary: Industry Terms 

This glossary will cover all of the common slang terms you might hear at the shooting range or at your local Powered by Silencer Shop dealer. We’ll cover suppressor definitions, gun range terminology, and other basic gun terminology. This blog is accompanied by a glossary of firearms legal terms and definitions 

This is not a comprehensive list, but we feel this covers most of the legal acronyms, NFA definitions, and basic gun terminology. If there are any others you didn’t see on this list that you feel should be here, let us know in the comments below! 

Firearm Industry Terminology 


Short Description 

Long Description 


Flat Dark Earth 

A specific type of coloring. Flat is the finished look, Dark Earth is the color. 


Second Amendment 

The reason that we have all of these awesome acronyms. The right to bear arms, as written in the Bill of Rights.  

A-2 Birdcage 


A specific type of flash hider where the prongs are enclosed. Most often recognized as the muzzle device of choice by our Armed Forces on the M16 and M4 platforms. 



A sacrificial substance used to absorb or disperse heat by burning off, thereby reducing the sound. When you hear someone talk about shooting a suppressor “wet,” the substance they use in the silencer (water, wire pulling gel, suppressor foam) is referred to as the ablative. 



An inexpensive, flexible, lightweight metal more commonly used for the construction of rimfire and pistol silencers.  


Any Other Weapon 

A type of firearm that is not defined by the major ATF categories, such as SBR, SBS, Silencer, Pistol, Rifle, or Shotgun. Firearms not under the designation of these categories still need to be registered as an AOW.  


Active Spring Retention 

A SilencerCo mounting system that was originally used on the SWR Specwar.  It has since been incorporated into all of the SilencerCo rifle silencers.  

Baffle Geometry 


The way the baffles are shaped directly affects how the gases flow through the silencer, resulting in changes of blowback and sound. 



The rifled tube of your firearm that the projectile travels through.  


Bolt Carrier Group 

The bolt chambers, fires, and extracts a casing in the AR15 platform.  



A term to describe gases moving in opposition to the direction of the projectile. For instance, when you shoot and the gases go forward, but some of the gases blow backward due to added resistance of a silencer at the muzzle of a firearm. 



Aka suppressor, aka silencer. It has many names but refers to the same awesome thing. 

Carbon Fouling 


The residue from the combustion of gunpowder. To some degree, a thin layer of residue can help with attenuation in rifles, but in the case of pistol and rimfire, the suppressor needs to be cleaned in order to prevent too much build up.  

Click Together 


A particular method of baffle assembly where the silencer baffles click onto one another in order to seal the hot gases inside of the baffles, thereby preventing fouling on the inside of the tube.  


Close Quarters Battle 

A fighting style used by the military. In silencers, this term is often used to denote a shorter or more maneuverable silencer. 



A measurement of sound.  


Destructive Devices 

The term used for explosive devices such as commercial explosives, flash bangs, grenades, etc. 


Direct Impingement 

This is a reference to a gas system common to AR's. 



The simplest type of mounting system where the suppressor directly threads onto the host firearm. 



The endcap is screwed on to the end of the silencer. Generally used for modular silencers when changing lengths. You can also change an endcap out to change the bore size to match the caliber of the host firearm. 


Flash Hider 

We've covered a lot on muzzle devices before. But a flash hider is a device used to do just that - reduce the muzzle flash while shooting. See also, muzzle brake. 


Feet Per Second 

Generally used in the silencer world in the context of determining whether or not a round is considered subsonic. FPS can generally be found on the ammo box.  


First Round Pop 

FRP is the louder sound made from the initial blast of the firearm due to the amount of oxygen in the suppressor. Subsequent rounds fired after the first round will be a little bit quieter.  


Flash Signature 

The flash emitted from the barrel of a firearm when a round is shot through it.  



A reference to grain weight of projectiles and/or powder. 


Home Defense 


Hydro Sonic 


Water based cleaning system that vibrates the water molecules to clean metal materials. 


Inner Diameter 

Commonly used to describe the inside diameter of a silencer tube. 



An abbreviation for the German word: "Kurtz." Meaning "Short." 



One of the major styles of baffles where the profile view of the baffle resembles the letter “k.” 



Direction threads are done on a barrel or muzzle device. It is a common reference when describing thread pitch. 


Lower Receiver 

In reference to a section of an AR that houses the fire control components. By law, the lower of a firearm is the section that holds the serial number. 



This letter is used after model names to represent that the can is modular. 


Muzzle Brake 

We've covered a lot on muzzle devices before. A muzzle brake is intended to reduce lateral recoil of a firearm by specifically controlling escaping muzzle gasses. See also, flash hider. 


Minute of Angle 

A method of measuring angle in relation to distance.  This is most often used to describe the precision of a firearm where a one inch group at 100 yards represents 1 MOA, 2 inches at 100 yards indicates 2 MOA, etc.  



Used when describing the inner part (baffles) of a suppressor being machined out of one solid piece. 

Muzzle Device 


This term is used to reference a device that screws onto the end of a firearm. Examples of muzzle devices are flash hiders and muzzle brakes. 



Also known as a booster, the Nielsen device is used for pistol suppressors in order to compensate for the recoil of the host firearm. Another common technical term is “linear decoupling device.” 


Overall Length 

Applies to length of silencer or how the ATF defines specific firearms in order to determine what category they are in. The OAL is a requirement on every NFA form (excepting oddballs like auto sears). 


Olive Drab Green or Outer Diameter 

A specific type of green, common in military applications.  


Outer Diameter 

The largest diameter of a silencer.  


Pistol Caliber Carbine 

A rifle that fires traditional pistol calibers such as the MP5 shooting 9mm. 


Personal Defense Weapon 

Though not legally defined, PDW’s are often a very small, subcompact firearms. 



The part of the nielsen device that threads onto the barrel that allows the weight of the silencer to disconnect from the tilting barrel of a Browning action pistol.  


Point of Aim 

Where you are aiming (or where it looks like the bullet will hit). 


Point of Impact 

Where you actually hit (or where the bullet makes the impact). 


Pounds Per Square Inch 

A measure of pressure most commonly referred to when talking about catridge specifications. 



Also known as QA (or Quick Attach). A type of mount that allows you to quickly mount or remove a silencer. Generally, a female mount on the silencer that accepts a male muzzle device.  


Right Hand 

Directions threads are done on a barrel. It is a common reference when describing thread pitch. 





Rate of Fire 

The rate at which a firearm can launch a projectiles. Typically described as round count/time. 


Short-Barreled Rifle 

A rifle with a barrel length less than 16 inches. SBR's are registered through a specific NFA form.  


Short-Barreled Shotgun 

A shotgun with a barrel length of less than 18 inches. SBS's are registered through a specific NFA form.  



German for: sound damper. The suppressed version of a firearm. For example, the MP5 vs. the MP5-SD. 


Serial Numbers 

The social security number of firearms and some firearm accessories.  



A circular "washer like device" that is used to time a muzzle device correctly onto a host firearm.  



A particular section of a barrel, at the base of the threads, but before the start of the barrel, that allows the object being threaded on to the barrel to have a perfectly flush mount onto the host firearm. The two forms of shoulders are taper and square.  


Stainless Steel 

A tough, flexible metal resistant to corrosion. These steels can generally be used for the construction any silencer where a primary goal is durability as opposed to weight savings. Stainless steel, especially in rimfire cans, give you more options for cleaning as well.  


Subsonic Ammo 

The premise of a subsonic bullet is to have the projectile exit the barrel at a velocity that is slower than the speed of sound. 


Supersonic Ammo 

A reference to ammunitions where the projectile will always be faster than the speed of sound.  



These words refer to the same device. “any device for silencing, muffling, or diminishing the report of a portable firearm” per the ATF 


Suppressed Upper Receiver Group 

Adopted into the civilian market from a military acronym, SURG refers to an AR upper receiver that has in integrated silencer. 



In regard to the barrel or muzzle devices shoulder, a taper replaces the 90 degree shoulder on a barrel or device to create a more reliable/repeatable mating between silencer, muzzle device and/or barrel.  

Threaded Barrel 


A barrel that is threaded is used primarily to mount a silencer onto a host firearm (the alternative use is for an AR platform where a muzzle device would be mounted on). 



A metal with a high strength to weight ratio though more expensive than most stainless steels or aluminum.  


Taper Mount 

The most repeatable and accurate POI as far as QD goes. See also: Taper 


Threads Per Inch 

A measurement for the threading on a barrel.  



The outermost part of a silencer, generally covering the baffles. Common in user-serviceable silencer designs.  


Upper Receiver 

In reference to a section of the top section of an AR containing the upper receiver, barrel, handguard, etc.

Wet Tumbling 


A cleaning system that tumbles in order to clean metal materials. 

H1 Thru H-9 

Buffer Weights 

By changing the buffer weight, you can slow down or speed up the cycle of the gun. Altering the buffer weight helps compensate for the pressure added or taken away from the firearm.  


Over The Barrel 

Type of silencer where the silencer mounts over the barrel of the firearm.  This, in turn, reduces the OAL of the suppressed system at the cost of sound attenuation. AKA: Reflex 

FA (rated) 

Full Auto Rated 

In terms of suppressors, a can that is considered full auto rated is one that is built from specific materials in order to withstand the heat and pressure associated with a high rate of fire.