Why Are Guns Noisy?

I wrote “Is Pffffft-Pffffft the Sound of Silence” back in 2021 for another site because of a request that I clarify what a “silencer” really does to the noise of a firearm. Because of the continued public confusion regarding suppressor performance in the real (not Hollywood) world, and because it is still topical, I decided to give it a redux at my website. Of course, a silencer does not silence gunshot noise, so I’m using the more accurate term “suppressor.” I also added a note at the end where I address a present day issue.

Why Are Guns Noisy?

I imagine many of you grimace while watching TV shows and movies with “Ninjas” dressed in black running around shooting suppressed weapons that are highly effective against everything (and everyone) they shoot. Of course, according to video and film productions, non-military or police use of “silencers” is only for bad guys who silently kill people and then get away because no one, not even the victim, hears the single gunshot that kills. Seems like the only change up from this we see is a “double tap” in movies trying to appeal to watchers who have some video game knowledge of shooting, but the noise is still only a “pffffft – pffffft.” We know better.

Nevertheless, the main reason most of us invest the time and money to purchase and obtain a suppressor to use with pistols and/or long guns is to reduce the firing and downrange noise of gunshots. We realize we’ll likely never achieve the Hollywood “pffffft,” but what should we expect, noise-wise?

Silence Is Golden

Bear with me as I take you through a simplified explanation of gunshot noise sources. It may help you make informed decisions about gun, suppressor, and ammo purchases. In the process, I’ll focus on the biggest factor in noise, ammunition, but briefly mention the other factors regarding caliber and suppressors along the way. A shooter must consider other factors in addition to suppressor brand, type and performance. Ammunition choices, especially subsonic versus supersonic ammunition, play a huge part in the amount of noise suppression possible. I’ll use the military-sounding term weapon system because you must wrap your brain around the fact that this is what we are assembling when we make choices regarding a firearm + caliber + suppressor + ammunition.

As you may guess, I’ll lay out some of the basic facts regarding the performance of subsonic ammunition fired through a suppressed weapon system. Choosing the ammunition to use, based on its projectile velocity when fired in your weapon, is an important step, because a suppressor by itself does not affect all noise from the shot, and noise reduction is a big reason to purchase a suppressor.

Think about it – what noises result from firing a weapon system (besides the “oohs” and “ahs” from folks watching your Instagram-post-able shooting technique and cool gun accessories)? Starting from the butt-end of the system, we have the sound made by the action as it chambers, fires, extracts, and re-chambers a cartridge. This happens unless you use a bolt-action or other single-shot firearm. So, one way to reduce firing noise is to use a single-shot firearm.

Hey Buddy, Fix Ya Muffla!

Next, there is the sound of the explosion in the gun chamber as the cartridge fires. If you fire a large weapon system you might hear a distinct “ping,” but in small arms very little of that noise comes through the steel chamber walls. You usually hear the portion of that noise that comes out of the muzzle, and that noise combines with the noise created by the heat and turbulence of combustion gases expanding into the air. This is the noise we reduce by installing a suppressor on the muzzle.

Bullet, followed by pieces of bullet metal, leaving the muzzle. The turbulent, energetic gas is evident as the white cloud, with still-burning particles of gunpowder spraying from the barrel. Credit: Herra KuulaPaa, Caters News.

Glowing gas would be visible if a suppressor was not used. The energy dissipating from the gas cloud is a major source of noise from a gun shot.

Another noise is the sound of the bullet hitting the target, and we cannot do anything to modify that aside from shooting a different target.

Thwack!

The last noise is the sound a bullet makes after it leaves the firearm, if it speeds along at or above the speed of sound in the air (where most bullets travel). A supersonic bullet creates shock waves that spread out along the bullet’s path in a very similar manner to the shock waves created by supersonic aircraft and missiles; nearly everyone has heard the resulting “sonic booms.” The shadowgraph photo shows these shocks from projectiles. Most shooters never hear the shocks because gunshot noise overwhelms the “snap” of a sonic boom from a bullet, but if you are downrange and hear the shock wave, it is a sound reminiscent of someone firing a cap gun (small caliber gun, say .22 LR or .223 Rem) or slapping a wet flip-flop against a hard surface (large caliber gun).

Shadowgraph of projectiles traveling through air at about 1.5 times sonic velocity. Credit: A Davidhazy, Rochester Institute of Technology.

It happens that we can affect the noise of these sonic booms by firing subsonic ammunition, which eliminates the shock waves. The medium (usually air) through which the projectile is fired and the medium’s density (depends on temperature, humidity, and altitude) determine the local sonic velocity. You might correctly guess that it takes an involved computation using the results of several measurements to arrive at a precise sonic velocity, but a good rule of thumb is that the local sonic velocity is about 1100 to 1150 feet per second (fps) under the conditions most of us shoot (all the way up to 9,000 feet elevation under normal conditions).

Given this information, a shooter can consult the muzzle velocity information given by most ammunition manufacturers to decide whether particular ammunition is likely to produce a sonic “snap” when fired through a suppressed weapon.

Typical rifle cartridges, l. to r.: 3 x .300 AAC Blackout: 203 grain coated practice round, subsonic, handload; 212 grain plastic tipped hunting round, subsonic, handload; 155 grain match round, supersonic, commercial. 5.56 x 45 mm NATO Ball 62 grain, supersonic, commercial. 2 x 7.62 x 51 mm NATO: M80 Ball 147 grain, supersonic, commercial; M61 AP 150 grain, supersonic, handload. .30 – ’06 M2 AP 165 grain, supersonic, handload

Can We All Just Be Quiet For a Little While?

In some cases, the internal ballistics of the cartridge may make this impossible. Unless you are a handloader, finding subsonic ammunition in popular centerfire calibers is difficult. Even handloading subsonic ammo in many calibers is problematic, if not outright dangerous, so if extreme quiet is of supreme importance, this should influence your choice of firearm caliber. For more information about this particular problem, do some background research on the genesis of the .300 AAC Blackout caliber. If you do an online search, you’ll find several hours’ worth of reading on the topic.

Ruger American Ranch Rifle .300 AAC Blackout caliber, with Harvester 300 suppressor, and Leupold Mark AR 3-9 x 40 scope

Palmetto State Armory PA-15 multicaliber lower, with .300 AAC Blackout carbine upper, Omega 300 suppressor, Leupold Firedot-G optic and mount, and ATC Gold trigger

Palmetto State Armory PA-15 multicaliber lower, with .300 AAC Blackout pistol upper, Omega 300 suppressor, Trijicon MRO-C optic, SIG brace

Another Benefit of Using a Suppressor

Ammunition affects suppressed weapons systems’ performance in a different way other than noise, and in this case being suppressed may improve the performance with subsonic ammo. When firing subsonic ammo using a suppressor on semi-auto .22 LR caliber handguns and rifles or pistol-caliber carbines, the systems are often less sensitive to ammunition quality than when you fire them without a suppressor. Many of these semi-autos are blowback-operated weapons, in many cases making them finicky consumers of ammo. Suppressing these weapons increases the operating pressure, allowing them to use lower pressure (i.e., subsonic) ammo that normally is hit-or-miss in the unsuppressed gun when it comes to misfeeds and stovepipes. You may also find that suppressing your larger caliber gas-operated pistol- or carbine-length AR causes operating problems because of the higher operating pressure, unless you use subsonic ammo.

Hoplophobia

This year, several pro-2A organizations lobbied the U.S. Congress to remove suppressors (and other gun-related items) from coverage under the National Firearms Act of 1934 (“the NFA”), a U.S. law that regulates the manufacture, transfer, and possession of certain firearms and firearm accessories. The law imposes a tax on these firearms and requires their registration with the federal government, ostensibly to help control crime associated with their use. The Act got around being a direct violation of the Second Amendment to the U.S. Constitution by attempting regulation and control of arms via taxation, and by making a permittee wait months for possible permission to own these items. I suppose Congress originally included suppressors because of some fearful concept that only people using them for nefarious reasons would want to quiet the noise from firearms. Ever since then, the hoplophobes in the Government and media have fought removing suppressors from the NFA, even though their use in crime is non-existent. One supposes their reason for opposing removal is their fear that if you give us gun nuts an inch, we’ll become emboldened and want a mile. They are merely assuming we would act as they do in a similar situation, a classic case of psychological projection. In the meantime, those of us participating in the shooting sports wanting to protect our hearing must use uncomfortable and sometimes ineffective protection, or wait six months for some government bureaucrat to give us permission to exercise a constitutional right.

Why Are Guns Noisy?