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Testing and Evaluation: September 1998

By Al Paulson

Problem Solving With Low Signature Weapons, Part III

In previous issues of SAR, the first and second installments of this article examined how to use suppressed weapons for solving a wide array of tactical and public-relations problems. The preceding discussion focused on how to: (1) hide the fact that a shot has been fired; (2) hide the location of the shooter; (3) reduce public-relations and media-relations problems. This article will conclude the discussion by exploring the use of low-signature weapons to (1) enhance command and control; (2) preserve operator hearing, especially in confined spaces; (3) reduce the likelihood of detonation when operating in a potentially explosive atmosphere; (4) improve the quality and safety of live-fire training; (5) reduce muzzle blast and recoil; (6) safeguard human night vision and electronic night vision devices; (7) reduce the risk of so-called “friendly fire” accidents; (8) increase operational security, and (9) improve both practical accuracy and the speed of follow-up shots.

Reducing Muzzle Blast and Recoil

Dr. Rauno Pääkkönen of the Tampere Regional Institute of Occupational Health and Illka Kyttälä of the Ministry of Labor in Finland have conducted the most interesting research to date on the effects of rifle-caliber muzzle brakes and sound suppressors on such important performance criteria as muzzle blast, recoil, and accuracy.

For this particular study, Pääkkönen and Kyttälä used 7.62x51mm (.308 Winchester) hunting rifles that were threaded for muzzle brakes and sound suppressors. Two suppressors and twelve muzzle brakes were fired from bolt-action rifles with Lapua supersonic and subsonic ammunition, measuring sound signatures both at the shooter’s left ear and 10.9 yards (10 m) to the right of the shooter at a height of 63 inches (1.6 m). They measured recoil using a ballistic pendulum, which held the firearm at the end of a 39.37 inch (1.00 m) arm to which a weight was added to reduce the angle of rotation during recoil. Accuracy tests were conducted at the Lapua Oy range using a machine rest that incorporated a spring mechanism to absorb recoil. Here’s what they learned.

Muzzle brakes significantly increased the sound pressure level at the shooter’s ear, from an average peak sound pressure level (SPL) of 159 db without the muzzle brake to an average of 167 dB with muzzle brake. That 8 dB difference represents a significant increase in both discomfort and health risk. The muzzle brakes were effective, however, at reducing recoil momentum from 10.9 to 6.2 kg m/s, which represents a 43 percent reduction. Converting the SPLs to sound exposure levels (which include a time factoring to quantify health risk), then the data display a linear correlation between the sound exposure level and recoil momentum. In other words, those muzzle brakes most effective at reducing recoil also produced the greatest risk to the shooter’s hearing.

When the rifles were fitted with a BR-Tuote reflex sound suppressor, which only extends a few centimeters beyond the muzzle of the rifle, the ultra-compact but relatively loud muzzle can produced a modest net sound reduction of 18 dB at the shooter’s ear. The reflex suppressor did, however, reduce the recoil energy from 23 to 15 Joules, which represents a reduction of 35 percent. The more traditionally designed Vaimeco muzzle can extends well beyond the muzzle, and provides an impressive 35 dB sound reduction. Using Lapua subsonic ammunition, the Vaimeco suppressor delivers an amazing 41 dB reduction at the shooter’s ear.

When Pääkkönen and Kyttälä looked at how these suppressors affected accuracy, they found no difference in group size with or without either suppressor. The average point of impact did, however, move downward 60-70 mm (2.4-2.8 inches) at 100 meters (109 yards). Simply adjusting a rifle’s sights corrected for this phenomenon. My own experience suggests that many rifles will become more accurate with properly designed and installed sound suppressor since the weight of the device dampens barrel harmonics. Rifles with short, fat and stiff barrels may exhibit little improvement in group size when a suppressor is installed. But I’ve seen group size shrink from 1.5 MOA to less than 0.5 MOA with the addition of certain suppressors to some tactical rifles.

This research is relevant to tactical users, since recoil reduction is particularly desirable in weapons using a cartridge larger than the 7.62x51mm round. Using a suppressor with .300 Winchester Magnum rifles, for example, permits extended training without shooter fatigue. The suppressor also reduces the risk of both short-term and long-term hearing loss by the sniper, spotter, and training cadre.

Using a suppressor to mitigate recoil with the increasingly popular .50 BMG sniper rifles is especially valuable in both the training and tactical environments. Not only is fatigue a more serious problem with this big boomer, the recoil impulse of unsilenced .50 caliber rifles has separated more than one shoulder, thus rendering the shooters hors de combat for a period of months. Mounting a suppressor (such as the ones manufactured by SIOPTS, AWC Systems Technology, and SCRC) onto a .50 caliber rifle reduces the recoil impulse and thus reduces the risk of shoulder injury, while reducing overpressure that pounds the face and eardrums of the shooter. Of course, the other benefits of suppressor use are even more valuable with a .50 caliber BMG rifle, especially the reduction of muzzle flash and environmental disturbances that can disclose the position of the shooter.

There are two main liabilities of .50 caliber suppressors: they tend to be large and heavy. Since a .50 caliber sniper rifle is essentially viewed as a crew-served weapon because of its size and weight, the additional burden of a massive suppressor is mitigated somewhat. Size and weight are primarily relevant for military users of the .50 caliber rifles since the impedimenta carried by the modern soldier is already burdensome, to say the least. Law-enforcement deployment generally involves limited movement on foot and much shorter stalks than common to military operations, so the size and weight factors are somewhat more flexible. Nevertheless, the additional bulk added by a .50 caliber suppressor must be considered.

Enhancing Command and Control

Using suppressed weapons during an unconventional operation enhances command and control for several reasons.

Suppressors facilitate verbal communications both directly (by lowering weapon noise) and indirectly (by eliminating short-term hearing loss called temporary threshold shift experienced by the operator and nearby personnel). Gunshot-induced TTS can last for a day or more. Furthermore, severe TTS is a particular problem if unsuppressed weapons are used in a confined space such as a building, ship or aircraft. Temporary threshold shift not only impedes communication among the good guys, it also impedes the ability of the good guys to hear the movement and verbal communications of the bad guys. Furthermore, temporary hearing loss becomes permanent with repeated exposure, which will adversely affect an officer’s survivability, not to mention his or her quality of life.

The use of passive hearing protection devices (such as muffs or plugs) is incompatible with the maintenance of effective command and control. Active HPDs will permit effective command and control, but these electronic devices have their own technical liabilities and are subject to failure at inopportune moments. Suppressors are not subject to battery failure or a broken wire. Furthermore, the suppressor provides hearing protection while allowing the operator to monitoring tactical radio communications by using an earplug in one year while leaving the other ear free to monitor verbal signals from nearby team members as well as environmental sounds.

Preserving Operator Hearing

As already discussed, the use of suppressed weapons dramatically reduces the risk of both temporary threshold shift and permanent threshold shift. This is an important consideration during training as well as during actual tactical operations. It’s hard to overstate the value of using suppressors to reduce TTS and PTS.

Operating in Potentially Explosive Atmospheres

Both military and law-enforcement operations are sometimes conducted in environments with potentially explosive atmospheric conditions. Muzzle flash might cause ignition in such environments as chemical plants, oil refineries, and illegal drug labs. Using a suppressor, preferably with special low-flash ammunition, can reduce the risk of muzzle flash causing an explosion. Several approaches show promise: using a suppressor with wipes to contain the flash, and using a wet suppressor to prevent the flash.

The SCRC Model MK-26 suppressor is an example of the former. When mated to an MP5 submachine gun, this suppressor (unlike many designs) seems to eliminate ejection-port flash, which can also provide a source of atmospheric ignition. The safest route, however, is to use a manually operated, locked-breech weapon so that ejection-port flash is no longer a potential issue. Gemtech uses a combination of wipe and wet technology to quench the muzzle blast and a foam-sealed E&L hard plastic brass catcher to isolate any ejection port flash or hot powder residue from the atmosphere.

Arms Tech, Inc. manufactures a matched artificial-environment suppressor and low-flash ammunition specifically designed to minimize the risk of detonation when operating in explosive atmospheres, although each weapon must be individually tested to ensure the absence of ejection-port flash even with this system. The Russians use captive-piston ammunition, which contains the by-products of ignition within the cartridge case, in special silenced weapons that provide the safest solution to this operational requirement.

Arms Tech has also developed a captive-piston round for use in potentially explosive atmospheres. Called the 6mm Hazmat, this round and weapons for it are available for sale to government clients only in the United States. All of these technologies improve the odds for an operator who must shoot in a potentially explosive atmosphere. But no firearms technology provides an absolute guarantee that ignition will not occur upon discharge of the weapon in an explosive atmosphere.

Improved Training

As an NRA instructor, I’ve frequently used silenced .22s to help troublesome civilian students get over their fear of shooting a firearm. The technique even helps experienced shooters such as military and law-enforcement personnel improve their shooting fundamentals, since the exotic qualities of a silenced firearm increase their concentration on what they are doing, as well as the instructor’s comments. The use of a sound suppressor also dramatically reduces felt recoil and shooter fatigue. While this is a considerable factor affecting the concentration and endurance of civilian shooters, the armed professional also benefits from the reduced effects of muzzle blast and recoil. Experienced shooters can be trained for longer periods when using a suppressed arm in the more punishing calibers such as .300 Winchester Magnum. .338 Lapua Magnum, and .50 BMG.

If an individual is ever called upon to conduct a hunter safety course, another consideration relates to the health and well-being of young shooters. Small kids can find shooting muffs uncomfortable. In fact, the muffs may not effectively seal on their heads, so they may experience discomfort and even hearing loss as a result. Suppressors provide a practical alternative to hearing protectors for young shooters. Finally, using suppressors instead of hearing protectors makes it easier for the instructor to communicate with the students, which not only facilitates instruction, it also enhances the instructor’s ability to maintain safe and effective control over shooters on the firing line. This is an especially critical consideration with beginning students, who are more likely to exhibit unsafe behaviors.

Safeguard Human Night Vision and NVDs

A single muzzle flash can temporarily ruin the night vision of a sniper, and the flash of a big boomer like the .338 Lapua Magnum and .50 BMG can wash out the image from some Night Vision Devices. The recoil from a big boomer can even damage the electronic circuitry of an NVD mounted on a sniper rifle. Employing a sniper rifle with a sound suppressor solves both of those potential problems. This is particularly important with rifles of any caliber when using an NVD weapon sight with the gain cranked up to maximum for prosecuting targets under minimum ambient light, such as pure starlight conditions. Employing a suppressor under these conditions can be quite useful.

Suppressors are also quite valuable when employing NVDs in the CQB (Close Quarter Battle) environment. A suppressor will protect an operator’s NVD goggles from a tactically disastrous bloom or flare from his own muzzle flash, which can put some NVDs out of service for tens of seconds. When vulnerable NVD equipment is employed, it is advisable that every team member employ a suppressor or the muzzle flash from the weapon of a nearby team member could still generate a blinding bloom in each other’s goggles. This could not only put members of an entry team out of action at a critical juncture, the phenomenon could adversely affect the NVDs of security personnel guarding the team’s flanks, depending upon the sophistication of their night-vision sights. Finally, it should go without saying that each NVD should be retested prior to beginning every new operation.

Reduced Risk of “Friendly Fire” Accidents

As pointed out by suppressor and small-arms authority N.R. Parker in his outstanding technical manual, Tactical Uses of Suppressed Weapons, the use of silenced firearms can greatly reduce the risk of harming both team members and innocent bystanders due to so-called “friendly fire” accidents. Consider, for example, a number of tactical team members confronting a number of armed opponents in a large building or a ship. When all team members are using suppressed weapons and all opponents are using unsuppressed weapons, the location and positive identification of hostile opponents becomes much easier.

Then there is the matter of innocent bystanders. Consider a dynamic entry into a counter-terrorist situation where a small number of armed opponents are interspersed with a large number of hostages, such as in a bus or aircraft. A hostage is much less likely to panic and jump into the line of fire if tactical team members are employing suppressed weapons with subsonic ammunition as they move through the hostages to eliminate the terrorists. When combined with other advantages—such as the ability to hide the fact that a shot has been fired while moving from compartment to compartment, plus the preservation of operator hearing, plus enhanced command and control—it becomes abundantly clear that sound suppressors are very valuable tools.

Increasing Operational Security

This benefit of using a sound suppressor is a corollary to the problem of media relations, and relates to an extended operation such as might be experienced with a hostage situation involving multiple armed suspects and a large building. The electronic media will likely have large telephoto lenses and will be hungrily searching the area of operations for footage. If a sharpshooter discharges an unsuppressed firearm, real-time TV coverage could reveal the location of the shooter to the armed suspects if any of them is monitoring television coverage. This could subject the sharpshooter to counter-sniper fire or limit subsequent tactical options. Using a suppressed arm with supersonic ammunition will misdirect media attention away from the shooter and either toward the target area or circa 90 degrees from the bullet flight path. Using a suppressed arm with subsonic ammunition could hide the event from notice, especially one arranged some type of sonic camouflage.

Improved Practical Accuracy and Speed of Follow-Up Shots

As discussed earlier, sound suppressors tend to improve the accuracy of a precision rifle by dampening barrel harmonics, and suppressors also dramatically reduce felt recoil, which reduces shooter fatigue. The reduced recoil also enables the operator to improve his effectiveness in several additional ways.

For example, reduced recoil eliminates shooter flinch. It will prove useful in the following discussion to define flinch as “body movements (commonly the shoulder jumping forward accompanied by a jerking of the trigger finger) that move the rifle before the shooter feels any shock of recoil.” This potential problem gets worse as once moves up from the .308 Winchester to more powerful cartridges like the .300 Winchester Magnum and .300 Dakota. While this may seem like a penetrating glimpse into the obvious, the elimination of flinch improves practical accuracy.

The bigger cartridges may also generate an additional problem called anticipatory flinch. This is a phenomenon where the shooter operating a weapon with substantial recoil actually closes both eyes just before flinching in anticipation of the recoil punch. It’s pretty hard to place a precise shot with the eyes closed. One must see the crosshairs at the moment the trigger breaks. While closing the eyes in this fashion sounds like a stunt that would only be pulled by a rank novice or nonshooter, sniper instructors inform me that this behavior is not uncommon among armed professionals shooting the more powerful cartridges common in law-enforcement armories.

Using a sound suppressor eliminates both flinch and anticipatory flinch in 80-90 percent of observed cases. A suppressor also enables the shooter to see the bullet strike, which greatly speeds up the decision-making process involved in determining if a second round should be placed in the target. Reduced recoil also speeds up the acquisition of other targets should that be necessary.


Clearly, the use of sound suppressors and low-signature weapons should not be limited to SWAT and special-response teams, or to urban departments. LSWs also provide excellent tools for training, animal control, and reducing the likelihood of public-relations and media-relations problems. Whether employing a silenced .22 pistol to eliminate a poisonous snake from a garden, using a suppressed Camp Carbine kill a potentially rabid dog for laboratory analysis to possibly save a child from a horrendous battery of injections (note: the animal’s brain must be left fully intact for laboratory analysis!), fitting an integrally silenced 300 Whisper upper receiver assembly to an M16 for putting down problem deer at the county airport, or using a suppressed .22 rifle to flatten the tires of a potential getaway vehicle, LSWs can make the job easier and safer. Sound suppressors are valuable, versatile and under-utilized tools of the trade.

The preceding discussion is not intended to be the last word on the practical employment of low-signature weapons. Rather, I hope this discussion stimulates the creative process and the subsequent dialog on solving problems with low-signature weapons. These tools can be as versatile as the creativity of the persons using them. It is also worth pointing out that recent publications such as Paulson (1996) evaluate quality sound suppressors produced by many additional manufacturers not cited in the preceding discussion and Parker (1997) provides additional information regarding the tactical employment of sound suppressors.

Further Reading

Parker, N.R. 1997. Tactical Uses of Suppressed Weapons. ATI Star Press, Boise, ID. In press. $15 plus $2 s&h (single copies free if requested from Gemtech on agency letterhead).Available from Gemtech, P.O. Box 3538, Boise, ID 83703. Check, money order, or VISA ok.

Paulson, A.C. 1996. Silencer History and Performance. Volume 1, Sporting and Tactical Silencers. Paladin Press, Boulder, CO. 424 pp. $50 plus $5 s$h.Available from Wideworld, P.O. Box 1827, Conway, AR 72033. Check or money order ok (no POs or CODs please).

Manufacturers Cited

Arms Tech Inc., 5121 North Central Avenue, Phoenix, AZ 85012.

AWC Systems Technology, P.O. Box 41938, Phoenix, AZ 85080-1938.

Black Hills Ammunition, P.O. Box 3090, Rapid City, SD 57709-9827.

Engel Ballistic Research, Rt. 2, Box 177C, Smithville, TX 78957

John’s Guns, 3010A Hwy. 155 N., Palestine, TX 75801

Gemtech, P.O. Box 3538, Boise, ID 83703.

SCRC, P.O. Box 660, Katy, TX 77492-0660.

SIOPTS, 570A Industrial Park Drive, Newport News, VA 23608.

Sound Technology, P.O. Box 391, Pelham, AL 35124.

Special Op’s Shop, P.O. Box 978, Madisonville, TN 37354

SSK Industries, 721 Woodview Lane, Wintersville, OH 43952

Note: there are many other fine suppressor manufacturers in the marketplace in addition to those cited in this article.


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