The reality of firearm suppressors.

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Hello again. I’m going to stick on the topic of intermediate ballistics this week, but go into a bit more detail on silencers/suppressors¹. I hinted last week that I might go on a deep dive, and I’ve had a few questions about silencers, so let’s strike while the iron (or gun barrel) is hot.

As this post’s title suggests, we’ll debunk the myth created by Hollywood that a firearm can be completely silenced, reduced only to a “pew”. I’ll pull together some examples of silenced firearms and show what silencers/suppressors can and can’t do, and compare the noises you’d get to some other types of sound. Then I’ll go into the components which make up firearm noise: mechanical, sonic boom, and muzzle blast. Then I’ll discuss the advantages that silencers bring, even though they’re not as impressive as they seem in the movies. Finally, I’ll sum up by discussing the limitations of silencers and why they are not universal.

I included this clip from John Wick: Chapter 2 in last week’s post, but I didn’t give it the attention it deserved as a truly ridiculous piece of cinema. Really, it deserves its own post just like I did with The Expendables, it’s that ridiculous, but instead we’ll use it as an anchor for today’s discussion while we also pull in some other Hollywood examples. Thankfully for us, there’s no shortage of unrealistic silencers on screen. Here’s the John Wick clip again:

This warrants another entry in the Realism vs. Drama Hall of Fame:

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Even a quieter gunshot is still very loud

Gunshots are very loud things, so even when you eliminate most of their noise, they’re still loud. Last week I mentioned decibels, which are the unit of measurement of sound intensity level (i.e. loudness). Here’s a chart (you can find any number like this on Google) which compares the decibel level of some common things:

Decibels are a funny unit, designed to measure the wide range of sound pressure levels that correspond to loudness. For example, 180 dB is a billion billion times louder than 0 dB². I don’t know about you, but I can’t picture a billion billion anything. To make matters more complicated, our ears don’t respond in a linear way to sound pressure. It’s like they have their own algorithm in there to make sense of the world (your brain, I suppose). All you need to know is that:

• An increase of 10 dB is ten times louder, but sounds twice as loud
• A decrease of 10 dB is ten times quieter, but sounds half as loud
• An increase of 3 dB is a doubling in loudness, but is the smallest increase in volume we can perceive
• A decrease of 3 dB is a halving in loudness, but is the smallest decrease in volume we can perceive

We see that “explosion” tops out the scale in the chart above, at 150 dB. How does this compare with gunshots? The loudness of a weapon (or anything) depends on the strength of the pressure wave and how close the listener is to the source. The problem with the above chart is that there are no distances, but we do have some firearms data which is calibrated to an observer 1 m away from the gun:

Firing a…	…registers…
AT4 recoilless anti-tank weapon	187 dB (according to this source). Might be measured closer than 1 m.
Smith & Wesson 586 .357 Magnum pistol	169 dB
Remington 742 rifle (.30-06 calibre, standard 22″ barrel)	161.6 dB
Remington SP-10 10-gauge shotgun	161.4 dB
Glock 22 .40 pistol	159 dB
AR-15 5.56mm rifle	158.9 dB
.22 rifle	140 dB (no distance specified, this source).

For some context to these numbers, 187 dB feels 20 to 130 times louder than the pain threshold of hearing (115-140 dB). 160 dB feels more than twice as loud (and is actually more like 10x as loud) as the top of most decibel charts. 140 dB is the level above which hearing protection is mandatory in the workplace, no matter how short the exposure it.

So much for unsilenced firearms. What difference does a silencer make? Dakota Silencer (now known as Silencer Central) produced a handy graphic comparing the difference between unsuppressed and suppressed versions of common firearms³:

You might not be too impressed with this, but it’s quite a big difference hidden by the logarithmic nature of decibels. Let’s show it a different way:

The above diagrams might be based on over-optimistic marketing material, but scientists have found that silencers reduce noise by 17 to 24 dB (98% to 99.6%). This is a huge difference, but still results in quite a lot of sound energy out there, hence the gulf between reality and what Hollywood shows us. This video from Debunked explains it well:

With all that in mind, how does the infamous John Wick subway shooting scene look? Luckily for us, Moose with a Scarf has done the hard work of fixing the scene with more realistic-sounding pistols :

Why are guns so loud, and so hard to silence?

Gunshot noise has three different components

There are three distinct noises which make up the familiar (from Hollywood, if nothing else) gunshot sound:

There’s another noise associated with gunshots, and that’s the sound of the bullet striking the target. It’s not usually considered as part of the trifecta above because it happens somewhere else, but it’s worth bearing in mind when we think about the infamous subway scene: even if they magically managed to fully silence their pistols, how is no-one reacting to the sounds of lead hitting concrete and tile at 300 m/s?

Mechanical noise: metal-on-metal clanging

Guns are full of metal parts under spring tension which move back and forth multiple times per second. There’s no easy way to make this quiet. The bigger the gun, the most noise its parts make. If you’ve ever spent time in a draughty section room doing “dry drills”⁴ on a GPMG then you’ll appreciate the clanging noise that a machine gun makes. When you’re firing live ammunition, your cheek pressed to the weapon and your hearing protection in place, the “ping” of return springs and “crunch” of moving parts is what you notice most, since the frequencies of the muzzle blast have been attenuated by the earmuffs. 

Hollywood has a double standard here. On the one hand, gun cocking is always loud and dramatic, with a “CHK-CHK” to announce the fact that the wielder means business (even if they absolutely should and would have cocked their weapon earlier). On the other hand, silenced weapons leave out or minimise the noise of the very same cocking actions while the gun is firing, like this example from The American:

To eliminate this noise you need a special type of gun design that has internal parts which avoid harsh impacts. Alternatively, avoid automatic fire and rely on bolt action, like the Welrod pistol we’ll discuss below.

Sonic boom: the trade-off that comes with speed

The excellent illustrations above are from “Lookang many thanks to Fu-Kwun Hwang and author of Easy Java Simulation = Francisco Esquembre”, CC BY-SA 3.0, via Wikimedia Commons. Do you see how a supersonic object leaves a line (or a cone in three dimensions) of high-pressure sound waves. This is the boom, and it travels along with the object for anyone in its path to hear.

There’s not much you can do about the sonic boom, apart from using subsonic (slower than the speed of sound) ammunition. If you’re doing something sneaky in close quarters, this is probably fine. If you’re looking to engage a target accurately at range, now you’re in trouble, because less speed means your bullet won’t go as far and won’t do as much damage to the target if it gets there.

Muzzle blast: the bit we can do the most about

The last component of firearm noise is muzzle blast, which we discussed last week as part of looking at intermediate ballistics. This is the shockwave caused by the high-pressure gases from inside the barrel suddenly coming into contact with the outside world once the bullet leaves the barrel. These gases have been cooped up for so long and under so much pressure that they just want to go everywhere at once: the resulting shockwave is the characteristic bang we hear from a gunshot.

Silencers/suppressors address this shockwave with their interlinked chambers. These let the gases expand slowly before exiting to the outside atmosphere, as seen in the GIF below:

Slow motion view inside a firearm suppressor with a clear tube body
byu/jacksmachiningreveng ineducationalgifs

Think of the unsilenced firearm like a stadium suddenly opening its gates and trying to expel a crowd of 50,000 away fans who’ve just seen their team beaten badly. When these hungry, angry, and drunk fans finally make it through the gates, they will wreak havoc on the surrounding neighbourhoods, in the manner of a shock wave. The silencer is like a buffer zone of food stands, bars, toilets, and lines of riot police outside the stadium. Some fans won’t hang around, but some will get another drink, some will get some food, etc. The density and anger of the crowd is reduced, and the neighbouring streets feel much less of an impact.

All silencers reduce muzzle blast, but some firearms designers take it further, addressing all three elements of noise to get “whisper” quiet weapons.

Maximum suppression means addressing all three elements of noise

The Welrod pistol, developed for Britain’s Special Operations Executive (SOE) during WW2, was specially designed to be as quiet as possible for clandestine operations, by addressing the three aspects we discussed above:

• It minimises mechanical noise by not being automatic. Each round must be manually cycled, and the bolt is designed for smooth and silent operation. Rapid fire is not an option with this weapon, so you’d better make your shots count.
• It eliminates the sonic boom by using subsonic ammunition (.32 ACP, a standard police round of the time). This round is already just about subsonic, clocking in at ~300 m/s muzzle velocity, but the internal barrel of the Welrod is drilled with holes to allow gases to expand slowly and to reduce the bullet’s velocity even more.
• It reduces muzzle blast using the familiar series of baffles, but also includes three rubber “wipes” or discs through which the bullet must pass. This further slows the release of gases during firing.

The cutaway below from Reddit clearly shows the barrel holes, the baffles, and the wipes (three dark-grey discs equally spaced along the front half of the barrel, with baffles in between).

Welrod integrally suppressed pistol [1210×1150]
byu/3rdweal inThingsCutInHalfPorn

The wipes in the Welrod are a consumable resource: their effect degrades with each round, and after a few rounds they no longer provide any sound suppressing effect. The firer needs to unscrew the front of the barrel and insert fresh wipes. Take a look at this Forgotten Weapons clip on the Welrod to see what a challenge this (and everything about the pistol) would be:

The Small Arms Review wrote about a noise test they did with a Welrod pistol in 2002. They fired the same type of round from an unsuppressed Walther PP (as a benchmark), then used a Welrod with well-worn wipes, then one with brand new wipes inserted. The measurements were done at 1 m, just like the results above. Here’s what they found:

The authors are at pains to note that the 122.8 dB sound measurement don’t tell the whole story, however:

Although the sound meter as an objective measurement is an important benchmark, it does not tell the entire story. There are a number of air (pellet) pistols with similar sound levels and some integrally suppressed .22 rimfire pistols with a slightly lower sound level. The subjective evaluation of the Welrod is that it makes less noise than these other weapons. Part of the reason is the locked breech. Although left-of-muzzle measurements of the .22-rimfire weapons may meter a lower sound level, subjectively they are louder due to right-hand ejection port noise. Further, the Welrod, with its wipes, significantly changes the sound characteristic with elimination of virtually all the higher frequency sounds. The sound of the Welrod being fired in a quiet location is almost imperceptible at 15 feet. In a noisy environment and with the muzzle in actual contact with the intended target, it would be inaudible even to the operator.

I’ll let you judge for yourself. Here’s a video of the Norwegian Arms & Armour Society testing a Welrod⁶. It’s certainly quiet, but it’s definitely not “Hollywood quiet.” Then again, this might be due to worn wipes. Still, it’s a whisper when compared to the other weapons they fire:

Conclusion: silencers serve a purpose, but come with trade-offs

A cynical armourer, like me in a past life, might roll his eyes and say that silencers are just another expensive way for more “elite” soldiers to differentiate themselves from the rest. A bit like Homer Simpson when he gets a gun:

The cynic in me would be wrong. Silencers do serve some very real purposes, even if they rarely make a shooter 100% stealthy:

• Location: Silencers make it harder for the enemy to judge where the sound is coming from. A muzzle blast occurs at a point and therefore can be traced back to its source. A sonic boom occurs along the line of travel of the bullet and reaches the observer after the bullet has already passed, making it harder to trace back to a source.
• Recoil and accuracy: By adding weight to the end of a barrel, and reducing the kick from expanding gases, silencers mean that barrels rise less due to recoil, improving accuracy.
• Hearing conservation: Bringing the firearm noise down by 17-24 dB, as we saw above, means a reduction of 98% to 99.6% in the total amount of sound energy hitting the ears of friendly forces. Or, if we want to talk about how this feels to our logarithmic ears, it’s a reduction of 70% to 81% in perceived sound. That’s quite significant, especially if you and your squad are laying down a base of suppressing fire. Apart from the health and safety aspect there’s also a tactical benefit, since acoustic trauma could impact a soldier’s ability to hear orders and think clearly on the battlefield.

They do have downsides, however, which is why you don’t see them on general issue:

• Cost. A silencer is a complex piece of engineering with many high tolerance parts. Its price is probably a significant fraction of that of the rifle it screws onto. This might be a worthwhile investment for a handful of special operators, but it’s a cost that most militaries will be unwilling to extend to general issue.
• Complexity. Silencers require more care, cleaning, and maintenance than a rifle. Their effectiveness depends on how well they are maintained, and that puts a giant regulatory burden on militaries if they are relying on silencers as part of noise control measures. How can you stand over the safety of a training exercise without inspecting every single silencer?
• Carriage. Silencers add weight to the weapon, as well as length, which can be awkward when operating in confined spaces. They also get hot and take a long time to cool down, posing a burn hazard.

For all of the downsides, there are legitimate responses. The cost of everything has been going up in recent decades⁷, so adding silencers is incremental rather than extortionate. Armourers already inspect weapon function prior to training shoots and NCOs and officers do cleaning checks in the field; adding silencers is not unthinkable. And the fully-laden weight of a soldier, like the cost of equipping them, has been rising in recent decades. What’s another couple of hundred grams?

The conventional wisdom is shifting. The new US Army M7 rifle, which is just coming into service, has an integrated silencer. The US Marine Corps were issuing silencers to their units a few years ago. Where the US moves in weapons technology, expect the rest of the world to follow.

What do you think? Will silencers/suppressors become standard military issue, or are they a niche item that will remain in the domain of the specialist? Let me know what you think in the comments below. One thing is for sure, they won’t sound like this:

That’s all for this week folks, thanks for reading, please like and subscribe to Military Realism Report using the button below. Please also share this article with anyone who might be interested. I realised that my old sharing buttons weren’t working very well, so I’ve changed them to something that’s (hopefully) better on mobile and desktop. I’m working my way through the back catalogue, doing the same.

Featured Image: DR. NO | James Bond dispatches Professor Dent, from Dr. No, United Artists (1962), via YouTube

1. Before we get started, a quick note on terminology. I usually call these things “silencers,” but I won’t get hung up on names, and “suppressor” is a common term for the same thing. There’s a school of thought that says we should call them suppressors because the word “silencer” implies that they completely remove the noise of the gun, and therefore contribute to the Hollywood myth. I don’t buy this. The silencer on a motorbike doesn’t kill the noise of the engine completely, and we don’t insist on calling it a suppressor. The original firearm suppressor was the “Maxim Silencer“: this term is not a Hollywood invention, even if they have fallen victim to the marketing hype. ↩︎
2. And here’s another funny thing about decibels. The way we use them to measure loudness, they are defined in relation to a reference pressure which is set at the threshold of human hearing. In most units, it would be meaningless to say that something is a multiple of zero (normally one is the reference), but 0 dB has a finite and measurable value. ↩︎
3. Yes, I know some values, e.g. the AR-15, differ by as much as 6 dB between the table above and the chart below. I think the table is useful because it defines what distance the measurement is from, and it’s in a .doc format as opposed to a picture—these things matter! A 6 dB difference is a difference of four times the sound intensity, which could be explained by halving the distance to the source, i.e. 0.5 m instead of 1 m. ↩︎
4. i.e. practicing loading, firing, and unloading the weapon but without ammunition, or with inert drill ammunition. ↩︎
5. For my younger readers, Concorde was a supersonic passenger aircraft which flew from New York to London and Paris. Yes, there was a time when you could get across the Atlantic ocean in under four hours without being a fighter pilot. ↩︎
6. As well as the noise, take a look at how awkward it is to re-cock (the shooter messes it up on his first try) and how easy it is to fire accidentally. ↩︎
7. Including the cost of litigation for hearing loss damage from veterans. In this context, silencers could entail a massive saving. ↩︎