To put the function of a sound suppressor it in its simplest terms, the suppressor works by slowing, redirecting and cooling the hot gasses created when the cartridge is fired. We can get into all kinds of scientific terminology, but that is the general function. If we relate it to something we are all familiar with, it will be easier to understand. Think of a balloon. If you release the gas very fast by use of a pin, it will make a “boom.” If you untie the knot and let go, the high-pressure gas inside will bleed out a little slower through the sputtering neck, making much less noise. If you hold the end when untied and slowly let the air out by using pressure of your fingers to control the flow, it will make very little noise, if any. A modern suppressor would fit roughly between the last two examples.
If you were to look at an X-ray of a silencer, depending on when it was made and who made it, you would likely see a few common features. There would be an expansion chamber close to the muzzle, a series of baffles that redirect the escaping gasses and end caps holding everything together. That is where the similarities end. Early sound suppressors used “wipes” that were constructed of a soft material that projectiles would pass through, closing up quickly behind them. Another effective type of suppressor was (and still is in some cases) an artificial environmental suppressor, or “wet can.” This suppressor typically uses no wipes, but performs best when a cooling liquid is introduced to the suppressor before firing. As the gasses cool they lose “energy” and are quieter than hot gasses.
Many modern suppressors use a baffle stack after the expansion chamber and before the end cap where the projectile exits. Current baffle shapes, types, materials and construction methods are sometimes closely guarded company secrets but two common styles encountered are “K” baffles and “M” baffles, named after the letter they most resemble if they were cross cut and viewed from the side.
To get an idea of how well a quality suppressor works, you can compare it to an automobile muffler. If you hear a dragster or stock car running on open headers with no muffler of any kind it will be very loud. It may damage your long-term hearing. That is the case with many unsuppressed firearms. If you listen to an automobile with a proper exhaust system, it will not be “silent” but will certainly not hurt your ears. That is a reasonable general comparison.
Another factor in firearm noise is that many projectiles travel at speeds above the speed of sound. The speed of sound is about 1,115 fps (at 32 degrees F at sea level). Elevation and temperature will affect that number. Anything breaking the speed of sound will produce an audible “crack,” and it is unrelated to the expulsion of gasses when related to shooting. Because of this sonic crack, it is unlikely a gunshot could go undetected, even with the best suppressor on the market. Subsonic ammunition can be used to alleviate some of the residual noise, but it is tough to meet the expectations created by the movie industry.
Positive Suppressor Use
Sound suppressors have some very beneficial uses, starting with training new and nervous shooters. The noise of firing a gun by those new to the sport is often associated with pain and recoil. The noise actually has little to do with either but perception can be powerful, especially when trying something for the first time. For that reason I have found great success in using suppressed firearms in training new shooters. Their enhanced comfort level allows them to concentrate on the fundamentals instead of developing bad habits, like a flinch they will fight to get rid of later.
Another benefit is avoiding scaring or bothering adjoining property owners. To many of us, the sound of gunfire from recreational shooting is as American as apple pie. Others, who may not have grown up in a rural paradise, find it bothersome and nerve-racking—maybe even to the point of unnecessarily involving law enforcement. Using sound suppressors allows you to go about your training, plinking, competing, hunting, etc., without broadcasting your activities over a wide area for miles around.
Using a suppressor is just being polite. If you are going to build a race track on your land because you are an off-road enthusiast and want to practice much more often than most people, you will seldom bother those in the surrounding area due to the muffler on your vehicles. If you have a shooting range on your property and desire to shoot whenever you can, a sound suppressor can allow you to shoot as much as you like and keep good relations with the neighbors. In some of the few European countries where firearm ownership is allowed it is considered rude to not have a “muffler” on a firearm, and they are sold unrestricted and over the counter. When Americans tell them suppressors are treated like “spy gear” in the United States and most people don’t use them they often ask if we drive our automobiles with no mufflers either, bothering everyone we encounter.