We’ve all seen them in movies. The secret agent screws a little canister onto the end of his pistol and suddenly, his guns shots are reduced to a barely audible “pffft”. So silent that removing a sword from its scabbard sounds like a cacophony by comparison! Because of this movie myth, we call these things “silencers”. They are actually called suppressors, which more accurately define what they do. This week we’re educating you by debunking this myth and setting you straight on how suppressors really work.
To understand how a suppressor works, we first have to understand what you’re hearing when a gun goes off. When a gun is fired, several noises are being made. First, and quietest, is the function of the gun itself. This is the mechanical sounds of the gun being operated. This is the sound of the trigger pulling, hammer falling, round being ejected, round being loaded, etc.. Second, is the muzzle blast. This is the load bang occurring as the result of the charge in the ammunition being ignited. Last is the ballistic crack or sonic signature. That’s the sound of the bullet breaking the sound barrier and typically occurs shortly after leaving the barrel.
The first sounds, those mechanical noises are very quiet and unaffected in any meaningful way by a suppressor. The last sound, that of the sonic signature, happens outside of the gun and is also not affected. It is possible to use sub sonic ammunition (bullets that, because of their charge, travel slower than the speed of sound) but the speed of sound is about 1,140 feet per second. Even handgun rounds travel at or beyond this. Even rounds traveling near this speed (transonic) may produce a sonic signature. Subsonic rounds are typically specialized rounds used for a specific purpose. It is safe to say that most commercially available ammunition (with the possible exception of some .22 caliber rounds) are at least transonic if not supersonic.
That leaves us with muzzle blast as a controllable sound. The booming sound of a muzzle blast is really just a volume of high pressure air expanding from the small volume of the barrel into the much larger volume outside of it. The result of the rapid expansion is a bang. Think of a balloon. When you take a pin to a large, full balloon, there’s a loud bang as it explodes. The bang is from that pressurized air in the balloon expanding all at once into the open air. Now, take the same balloon and, instead of popping it, gently open the filling neck to let the air slowly escape. There’s almost no sound. Suppressors use that same principle.
Typically, a suppressor is a container with an open volume of air inside of it. Its often filled with perforated baffles that allow the air from the barrel to expand at a slower rate inside the volume of the suppressor which is much larger. This slower expansion of air reduces the noise of the muzzle blast anywhere from 14 to 40db or so. On average, suppressors reduce the sound from the muzzle blast by about 30db or so. This happens to be about the amount that a decent set of ear protectors reduce the same noise to a shooter. So, in everyday use, a suppressor would reduce or eliminate the need for a recreational shooter to wear ear protection. The other benefit is that, because the release of gases is more controlled, felt recoil (the effect of the gun “kicking back”) is reduced by up to 30%.
Other benefits of a suppressor have a decidedly more military specific nature. By positioning themselves near hard surfaces, snipers can effectively “redirect” the sound of the sonic signature. That sound of the bullet breaking the sound barrier can be reflected off of a hard surface to mask the shot’s origin. This may not even be necessary in an urban area where the sound of the sonic signature alone may be nearly impossible to locate by ear in the midst of other noise. Suppressors also reduce flash. This can be helpful in night operations where exposure to a bright flash could disrupt night vision. Finally, it can reduce the risk of hearing injuries and disorientation when firing in closed spaces such as rooms.
Despite the science of suppressors, the general public and legislating bodies is still under the impression presented to them by Hollywood, that suppressors are magical devices that can reduce a gunshot to a whisper. In reality, the only effective use for them in the civilian world is as a hearing protection device and recoil assist mechanism. Yet, they are illegal to possess in several states (MA being one) and require a $200 tax stamp and a stack of paperwork from the ATF in the states where they are legal.