by Eugene Nielson
Sound-suppressed weapons are seeing increased use among today's law enforcement tactical teams. Some in the general public may question why a law enforcement agency needs sound-suppressed weapons. This is understandable, given the widespread misconceptions that are held about the true role of silencers. Hopefully, this article will dispel the misconceptions that are commonly held about firearm sound suppressors and give the reader a better understanding of the history, technology and tactical applications of these devices.
Sound suppressors are valuable tools that can save lives. They have a definite role to play in law enforcement. Fortunately, law enforcement agencies are beginning to recognize the value of using suppressed weapons during tactical operations.
The use of a suppressor eliminates any muzzle flash and sound
signature that can identify the shooter's position or disturb vision and hearing.
The lack of a muzzle-flash signature isn't only important in night operations.
It can also be absolutely essential when operating in a potentially explosive
environment, such as when raiding clandestine drug laboratories.
A sound suppressor can substantially reduce the recoil velocity and recoil energy of a firearm. Gas volume and gas pressure at the muzzle are major factors in the free recoil energy produced by a firearm. All other factors being equal, increased gas volumes and higher gas pressures at the muzzle will increase the recoil velocity and free recoil energy.
Free recoil energy is proportional to the square of the recoil velocity of the firearm. Doubling the recoil velocity quadruples the free recoil energy. Sound suppressors reduce the free recoil energy by suppressing the effects of the expanding powder gasses. They also add weight, slowing the acceleration of the weapon.
Maxim didn't set out to develop a sound suppressor for firearms. The Maxim silencer was a result of the younger Maxim's efforts to improve the gasoline-powered automobile. His research on the exhaust muffler led to the invention of his now-famous device. Although no sound suppressor completely silences a firearm, those who quibble over the use of the word silencer should take note of the fact that Maxim himself called his device a silencer.
Maxim's invention brought him both fame and notoriety. During World War I, the Maxim silencer was used by the u.s. Army to a limited extent on the 1903 Springfield rifle. Although the Maxim silencer never saw widespread use, public furor led to its prohibition in many states and in several foreign countries. As a result, Maxim stopped its manufacture in 1930. Federal restrictions were imposed with the passage of the National Firearms Act (NFA) of 1934.
The muzzle blast is the most significant source of sound that's generated by a firearm. A .22 LR handgun generates around 148 dB. A 9mm MP5 SMG generates around 157 dB. An M16 generates around 168 dB. Again, when comparing dB, always keep in mind the logarithmic relationship of a dB. Also keep in mind that the dB output can fluctuate by several dB due to differences in atmospheric conditions, i.e., temperature, humidity and atmospheric pressure.
Various combinations of components, such as baffles, spacers, packing material, mesh, expansion chambers, spiral diffusers, pressure relief ports and wipes, may be employed in a suppressor to "silence" a firearm. A relatively recent innovation is the use of artificial-environment technology, which use greases, oils or other fluids that cool the gasses for more effective sound suppression. Additionally, the use of artificial environment technology provides an increase in the efficiency-to-size ratio of the suppressor.
Wet technology is a common artificial environment that's being utilized for suppressors. Besides providing additional sound suppression by adding a small amount of water or light oil, many wet technology sound suppressors can be fired full of water without damage.
Lithium grease is another common artificial environment for suppressors. While the use of lithium grease allows suppressors to be very small and still be effective, it results in a higher maintenance requirement. The lithium grease will need to be frequently recharged. Recharging will typically need to be done after a couple of magazines have been fired.
As a suppressor accumulates fouling during firing, its effectiveness will deteriorate. The maintenance requirements will differ depending on the suppressor. Some baffled systems require nothing more than dunking in solvent to clean out the fouling. Other designs may require repacking or the replacement of "wipes" at the factory. It should be noted that silencer parts fall under provisions of the NFA.
A sonic "crack" will be produced downrange from the weapon if a projectile's velocity exceeds the speed of sound-about 1,087 feet per second (fps) at 32° F in still, dry air at a sea level pressure of 14.7 pounds per square inch, based on a 1987 calculation. This miniature sonic boom mayor may not be of consequence, depending on the mission requirements in which suppressed weapons will be employed. It should be noted that it is not possible to pinpoint the source of fire solely by using the crack created by the passing of a supersonic bullet.
Two methods may be employed to eliminate the sonic crack: the use of subsonic ammunition; or reducing the velocity of a bullet to subsonic by venting the gasses propelling the bullet via ports drilled into the barrel. Suppressed weapons with ported barrels utilize an integral suppressor.
Weapons with ported barrels and integral sound suppressors, such as the HK MP5SD, FAMAE SAF Silenced S1 and Sterling L34A1 SMGs, do not require the use of subsonic ammunition for effective sound reduction. They're designed for specialized applications that require fully realized sound and flash suppression. Because the suppressor is integral to the weapon, the weapon may not be used in a nonsuppressed mode.
Muzzle sound suppressors are more versatile than integral suppressors,
in that they can easily be removed when sound suppression is not necessary.
If subsonic ammunition is employed, muzzle suppressors are often every bit
as quiet as an integral suppressor. Because they do not reduce the velocity
of a bullet, higher terminal velocities are possible for applications in which
a sonic crack is not an important tactical consideration.
Although generally of little tactical consequence, if absolute sound suppression is necessary, a single shot or manually operated action will also be necessary. Early examples include the World War II era Mk I Hand Firing Device, DeLisle Carbine and the Sleeve Gun, which had silenced mechanisms.
It is interesting to note that, although we have come a long way in suppressor design, the Mk I Hand Firing Device (.45 ACP) is still the standard by which modern suppressors are compared. During testing conducted by the U.S. Army's Foreign Science and Technology Center (FSTC), the World War II vintage weapon test fired at an average sound level of 117.4 dB.
If semiautomatic or fully automatic firearms are employed, there will be noise from the action cycling unless some provision is made to prevent the action from cycling. Examples of pistols with this provision include the Smith & Wesson Mk 22 Mod 0 pistol, nicknamed the Hush-Puppy, developed for U.s. Navy SEAL Teams during the Vietnam conflict, and the Soviet/Russian Makarov P6. Although a slide lock was originally specified for the new .45 ACP HK Mk 23 USSOCOM pistol, developed for U.s. Special Operations forces, that requirement was dropped prior to production.
The semiautomatic functioning of pistols with Browning-type tilting barrel unlocking systems, such as Glock, SIG, Browning P35, M1911, Smith & Wesson and Walther P88 and P99 pistols, may be impaired by the weight of the suppressor on the barrel. To overcome this problem, lighter weight suppressors or recoil enhancing accessories may be employed. Lightweight, artificial environment suppressors are preferable for this type of weapon.
Tactical Operations' new Special Purpose 9 (SP9) sound suppressor is an excellent example of a lightweight, compact suppressor for 9mm pistols that allows reliable functioning of Browning-design-type pistols, as well as use of the pistol's standard sights. The SP9 utilizes a state-of-the-art baffling system and artificial environment (lithium grease) for maximum performance. The SP9 provides outstanding performance and complete suppression of the muzzle flash signature.
Any comparisons between suppressors need to be carefully considered, since the method of testing that's utilized by manufacturers may vary from manufacturer to manufacturer, making comparisons difficult, unless one has the details as to how the testing was conducted. u.s. military requirements for testing are specified in MIL-STD-1474C.
While silencers may have an image problem in the eyes of the general public
and some police administrators, they are, nevertheless, valuable tools
in the arsenal of today's law enforcement tactical teams and military special-operations
units. Their true role is far removed from that of the sinister devices
portrayed in the popular media.