A couple of years ago I wrote a three-part series for Sniperworx.com on suppressors. Late in 2010, I got a couple of requests for a survey; the individuals were looking for recommendations; however, FOG HORN doesn’t endorse or make recommendations. Instead, we approach any given product or technology on its own merit and compare it to what we view as minimum requirements. If it meets that criteria then it meets it.

With that in mind I’ll get started with the task at hand, which is to provide an overview of suppressor technology – 2011, and who the players are. Look for one article per week on suppressors and the current state of technology.

In this week’s piece, I’ll provide a background of what suppressors do and how they do it, and why suppressors are used

Suppressors are not silencers and silencers are figments of Hollywood’s imagination. A suppressor is a tube that attaches to the muzzle of a firearm, made of varying lengths and diameters, housing internal components and materials broadly referred to as baffles. A suppressor traps hot high pressure gases exiting the weapon’s muzzle, reducing pressure and temperature sufficiently to reduce or eliminate muzzle blast. It accomplishes the task using a series of chambers separated by baffles; which allow hot gasses to expand and cool. The baffle also disrupts and adds resistance to the expanding gas so that it drops in energy. Fore example, a 5.56 round generates an excess of 50,000 psi in the chamber and bore, a suppressor will act on that gas to reduce its temperature and velocity so that gas pressure, at the exit point, is in the order of 30 to 20 psi; thus reducing or eliminating the muzzle blast. In order for a suppressor to be highly effective its internal volume must be 20 to 30 times larger than the weapon’s bore internal volume. Therefore, shorter suppressor will usually be larger in diameter and longer suppressor will have a smaller diameter.

A weapon’s sound signature comes from the weapon’s muzzle blast, the noise generated by the weapon’s action and ballistic noise. Ballistic noise is the loud crack made by the projectile in-flight as it travels above the speed of sound. A suppressor does nothing to eliminate the weapon’s action noise nor will it alter the projectiles ballistic crack. The only way to eliminate ballistic crack is to use subsonic ammunition, this is a load that will keep the muzzle velocity below the speed of sound.

An important point to note, when discussing ballistic crack, is that the speed at which sound propagates is not a constant of 1100 fps. It is dependent on atmospheric conditions – principally temperature, relative humidity and barometric pressure; so, it is possible that you will still experience ballistic crack when firing a subsonic round – this has happened to me on more than one occasion.

Most subsonic rifle loads are designed to deliver 1030 to 1050 fps in muzzle velocity when fired through an unsuppressed bore; however, when you install a suppressor they will pick up, on average, an additional 20 to 40 fps in velocity – this phenomenon is called freebore boost. So, a round loaded to 1050 fps will exit the suppressor at 1070 to 1090 fps, or more. If atmospheric conditions are such that sound propagates at a lower speed, you will experience ballistic crack.

Therefore, the primary function of a suppressor is to reduce or eliminate muzzle blast; however, there are secondary benefits. Suppressors, in most designs, will eliminate muzzle flash, reduce recoil and reduce dust signature. Since they reduce or eliminate muzzle blast, they remove a loud noise point source making ballistic crack and weapon action noise hard to localize.

When considering suppressors the requirements at the top of the list are muzzle blast and muzzle flash elimination or reduction, and all else is secondary.

In my next posts, I’ll expand on my closing sentence; giving it the explanation it deserves. Because mounting options, recoil reduction and other benefits deserve amplification and discussion.