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Page Gunwriters 15.12.1999:
The Use of Firearm Sound Suppressors for Wildlife Management
by Mark White
The world of suppressors is a relatively new one for many of us. With any new concept
there is a body of knowledge that must be absorbed in order to make that concept work
effectively. A suppressed rifle that is truly quiet is an incredibly useful tool for the
wildlife management community. We hope that the information contained in this article will
give you a good start on what needs to be known before one can begin operations with an
accurate suppressed firearm.
Here, Mark White prepares to fire his creation. The Classic
Ultralight system handles extremely well. Photo courtesy Alan C. Paulson, author of the
book Silencer
History and Performance.
How It Used To Be
My first exposure to animal control occurred as a kid growing up in the late 40s. Buffalo,
N.Y. was overrun with pigeons at that time, with the disease and filth that such a
situation carried with it. Two gray-haired old men in an equally gray old van were doing
their best to make a dent in the population. I was told that they were on a salary from
the City of Buffalo. The van cruised the streets of the city with impunity, and whenever
the old men saw a large flock of pigeons they stopped. Each carried a filthy Winchester
pump gallery rifle with iron sights, chambered in .22 Short. The men shot in front of
anyone, at any time, and they rarely if ever missed. The rule was one shot per bird, so
wounded survivors were often dispatched with a crushing blow from the butt of a rifle. The
old van was labeled "Buffalo Pigeon Control". Birds were loaded into
the back with large pitchforks, and the van made several trips to the city landfill each
day to dispose of the carcasses. Every once in awhile there would be a minor confrontation
with a shocked resident, but any complaints fell on deaf ears at city hall in those days.
How times have changed.
How It Is Now
Today one must keep a very low profile, doing this sort of work at odd hours and with as
little fuss and commotion as possible. One wouldn't think of blazing away in full public
view during rush hour today. The rules of engagement in today's world are: Don't draw
attention to yourself. Enter, work and leave quietly. Leave no trace. Pack carcasses in
opaque plastic or fiber bags for disposal. Never leave empty shell casings where they can
be found. Shoot from cover whenever possible. Use a firearm that is small, drab and
nondescript. The public at large equates size and noise level with power, lethality and
danger. The longer and flashier and louder a gun is, the more repulsive it is to them.
Walk quickly away from any possible confrontation with activists. Never engage an activist
directly. There will be an argument you can't win. Sidestep or evade whenever you can. Use
police or security personnel to run interference between you and angry activists whenever
possible.
Firearms and Silencers
While traps and poisons may have their place, there are many situations where a firearm is
the most expedient solution to the problem at hand. At this point I should mention that we
own a small company called Sound
Technology, which has supplied municipalities and private contractors with firearm
sound suppressors over the past twenty years. For the most part, we supply sound reduction
devices for small caliber arms – primarily .22 LR rifles, a few pistols, and an
occasional .308 rifle.
In most cases, sound reduction devices are being sold and used to eliminate or reduce
problems with public relations and activists. Loud gunfire noise draws human attention and
resentment like a magnet; in fact it is the sound most hated and feared of any category of
noise pollution. A properly made suppressor typically reduces firearm noise below the
threshold of human attention, and disguises it to the point where a firearm sound
signature can no longer be recognized as a gunshot. Our experience has helped us to
recognize what works and what doesn't. There are some commonalties that bear mentioning,
and some things that simply aren't worth doing. A little education and common sense will
save a lot of grief later.
Ammunition and Ballistic Crack
With regard to public relations, quieter and farther from public
view are always better. In some cases and with some species, one has to worry about
overpenetration and damage beyond the primary targets. Fortunately there is a wide
latitude of ammunition available today. For pigeons and small-bodied rodents inside
hangers, factories and warehouses, a Mexican company called Aguila makes a tiny, 20-grain
projectile powered only with priming material. The small pointed projectile is mildly
accurate at short range, travels at a sedate 400 (+or–) feet per second (fps), and is
very quiet in any weapon, even those which are not suppressed. It is typically more
accurate and more reliable than the oft-used .22 CB Caps and CB Longs. It will not
penetrate most roofing metal, and usually won't break windows.
Aquila .22 SSS - Sniper SubSonic rounds. GOW archive photo.
Before going further, I should speak to the subject of sonic or ballistic crack, the
phenomenon where any bullet that travels faster than 1,100 fps generates a noise
resembling an unsuppressed .22 rifle being fired. In low-profile situations all bullets
should travel 1,000 fps or less, safely below the threshold of sonic crack. Bullets
traveling at or below 1,000 fps emanate a barely audible whizzing sound, while those
traveling at or beyond 1,100 fps generate a CRACK! that will wake the dead, by comparison.
The requirement for a low bullet flight noise eliminates the so-called high-speed, garden
variety of .22 rimfires and .22 Magnum rimfires from consideration. Even if these are
silenced, the crack of supersonic flight noise is still so loud that the modification
usually isn't worth the effort and expense. If one is going to have a sonic crack with a
suppressed firearm, he might just as well have a more powerful rifle with greater range,
like a .223 or .22-250, since the sound level from a distance is about the same. For true
silence one must avoid the sonic crack like the plague. One wants velocity very close to
1000 fps, but not beyond that figure, since the risk of a bullet going supersonic on a hot
day is too great.
In the firearm sound suppression industry a tremendous amount of effort has been expended
toward limiting the velocity of common high-speed .22 LR projectiles. Typically this is
done by shortening barrels by either cutting them off, or by drilling holes (ports). For a
combination of reasons we have found that barrels shorter than four inches are not
particularly accurate, while barrels between six and seven inches long are as accurate or
are more accurate than .22 LR barrels up to thirty inches long. We have suppressed
literally hundreds of Ruger MK II target pistols with 5.5-inch bull barrels, and we rarely
find one that won't print a tight group when test fired. We have also suppressed a number
of similar pistols with barrels four inches and under. We almost never find a barrel
shorter than four inches that is reliably accurate. Because the high-speed .22 rimfire
cartridge is extremely efficient, we don't often use a rifle or pistol barrel
substantially over six inches long, since high-speed .22 bullets fired from longer, solid
(unported) barrels usually generate a ballistic crack. For the record, a .22 LR barrel
will generate its maximum velocity within fourteen to sixteen inches. We have done several
barrel-cutting experiments to prove this to our satisfaction. Anything longer than
fourteen inches will slow the projectile down a bit, and increase bore leading. In recent
years we have adopted the practice of physically welding eleven-inch suppressor tubes to
six-inch rifle barrels in order to avoid problems associated with a federal law concerning
rifle barrels shorter than sixteen inches. In Canada the law discriminates against rifle
barrels shorter than 18.5 inches, and sound suppressors may only be owned by
municipalities, police and military. In the United States sound suppression devices may be
owned by qualified individuals and corporations in 33 states, and by municipalities,
police and military organizations in any state. If a contractor is prohibited from owning
a silenced firearm in a particular state, and if he or she works for a county or
municipality, it is possible for the governmental entity to own the device while the
contractor uses it.
Getting back to .22 LR ammunition, there are times when the greater power and range of
standard 40-grain projectiles are required. In these instances, we often recommend
Winchester Dynapoint .22 LR ammunition (available at K-Marts across the country) as an
accurate, consistent, clean-burning round that will stay subsonic in relatively short (six
to ten inch) barrels. For those who have longer barrels, Remington, Winchester, Lapua,
RWS, Nobel and Aguila all manufacture special subsonic rounds (some are hollowpoint) that
are usually subsonic in most long rifle barrels. CCI manufactures an unusually hard lead
bullet with a small flat on its tip especially for small game. Appropriately called the
SGB (small game bullet) these are very accurate and penetrate well – for tougher
targets such as rabid coyotes, feral dogs & hogs, etc. Unfortunately the SGB exits at
1,400 fps from a sixteen-inch barrel, but it is subsonic out of a six-inch barrel.
Moving up the .22 rimfire ammo line, the Lapua Scoremax features a 48-grain, subsonic
bullet with great accuracy potential. The heaviest currently available round in .22 LR is
Aguila's SSS (sniper, subsonic), a 60-grain projectile in a .22 Short case. These are
fairly accurate, and have a typical muzzle velocity of about 750-fps from a six-inch
barrel. They have a velocity of 890 fps when fired from a fourteen inch barrel, and may
have more problems with trajectory than most other rounds. They are very quiet when fired
from a suppressed weapon with a fixed breech. When fired from a semi-auto, suppressed
weapon with a barrel over 6 inches the shortened cartridge case often breaks the seal of
the chamber before the pressure has dropped, leading to a loud escape of gas and particles
from the action area, hence we usually fire these rounds from bolt-action rifles. The SSS
penetrates about 40% more deeply than a standard .22 LR round. It is reliable in
bolt-action and pump rifles, but will not always be reliable in semi-auto rifles. It
usually feeds and functions properly in the standard of the industry, Ruger's MK II,
KMK512 pistol with a 5.5-inch bull barrel. The SSS may overpenetrate when fired into dog
and deer-sized targets, hence one should only use it in rural areas where a safe backstop
exists.
Most of the rounds mentioned sell for between 2 and 4 cents each, except for Scoremax,
which is about 18 cents a round in the United States. If one has a particular rifle or
pistol, it will pay to fire various brands of different ammunition at test targets to
determine which is the most accurate, since some brands and lots will tend to be in better
harmony with a particular barrel. Avoid hyper-velocity rounds such as Stingers and Vipers,
since they are very loud and are usually not accurate.
Weapons
Silencers come in two basic forms, integral and muzzle can. The integral looks simple, but
it is far more complex. The muzzle can is the simplest and will cause the user the least
amount of trouble. An integral system has holes (ports) bored in the host weapon's barrel,
with the body of the silencer an integral part of the weapon. A muzzle can is essentially
a separate silencer, either welded to or screwed on to the end of the barrel. 
Ruger 10/22 with Tasco ProPoint adjustable dot scope and Sound
Technology's "M" integral can permanently mounted to the muzzle. Photo courtesy
Chris Halbrook.
While the integral system used to have an edge on the rate of sound reduction (no longer
the case with advanced designs of muzzle cans) there are two inherent problems that must
be dealt with. The first problem has to do with the difficulty of deburring holes drilled
in a weapon's barrel. Access to the holes inside the barrel is a problem, and many holes
were never deburred properly, with the result that sharp edges and bore protrusions
deformed passing bullets and packed the holes with the scrapings. Over time the suppressor
picked up so much lead that it weighed several pounds more than it should have. Even if
the holes were properly deburred, lead vapor was driven through the holes, eventually
clogging the passages. Water vapor is formed with the burning of gunpowder, and is usually
trapped inside an integral suppressor, similar to what happens with a car's muffler. There
is no easy escape route for the water, and it will cause corrosion problems. While there
are techniques to limit these problems, the bottom line is that integral silencers have a
finite longevity. Some integrals are better than others, but all will eventually suffer a
degradation of performance from lead buildup and corrosion.
The muzzle can may not look as benign as an integral (its purpose is more obvious and its
profile is apparent) but neither does it suffer from the same problems. Some muzzle cans
tend to unscrew as they are fired, but this problem is usually cured with left-hand
threads that oppose the direction of the rifling twist. Those cans that are bonded or
welded to a barrel won't come loose, which will prevent problems with a shifting zero.
Water buildup will be a much smaller problem, and this can be countered with the use of
anti-corrosive oil, and by storing the weapon in a muzzle-down position with the action
open. Liquid water will run towards the suppressor's muzzle. Evaporation will take place
if the weapon's bore remains open, allowing air circulation. Large caliber weapons are
more affected by water buildup than the .22 LR, with its tiny charge of powder. Also, .22
LR bullets are lubricated with an oily, waxy coating. This distributes itself over the
barrel's bore, preventing exposure to corrosion. While muzzle cans may look more obvious,
they are the professional workhorses in the animal control industry.
The common .22 rifle will take care of most situations encountered in an urban setting. If
the shooter does his part with care and skill, the standard 40-grain bullet will quietly
and humanely remove even fairly large animals from an area. The rifle must be accurate,
and that entails having a good free-floating barrel, a good trigger, a good scope
(properly sighted in), and ammunition that fits the weapon well. A single shot must be
very carefully placed into the lower rear portion of the brain area (medulla oblongata) of
the animal to be collected. Such a shot will effectively sever the connection between the
brain and the central nervous system (CNS), preventing further muscular movement and
immediately terminating the life of the animal in question. Because of the limitations of
the .22 cartridge (primarily drop) the shot must be delivered within 100 yards or less,
and it must not be rushed. A properly suppressed weapon will be very quiet. The dominant
sound will be the plop of bullet strike. Animals have much better hearing than humans do;
yet a properly suppressed weapon will not normally frighten them away. Those animals that
would run from the sound of a regular firearm will probably not be alarmed by most
suppressed fire delivered from a bolt-action rifle. This will have to be taken on a
case-by-case basis, since all suppressors are not created equally. The primary reason for
using a suppressor is to shield urban residents and activists from the awareness of a
collection operation, so that the contractor can perform his mission without the hassle
that public awareness would bring. A side benefit of an extremely quiet weapon is that
many animals can often be collected at one time, since there is no loud report to frighten
them. A properly executed shot will drop an animal immediately, like a sack of potatoes.
There will be no spasms or violent movements that could alarm others in the area.
The Sound Tech suppressed Ruger 15/22 is available with a 16 inch
stainless tube (shown) or a 22 inch stainless tube. Photo Courtesy Alan C. Paulson.
Varmints such as coyotes in rural settings are normally more wary, and may not allow a
contractor to approach closer than 300 yards. Here a centerfire rifle in the .223 to
22-.250 category is called for. Even though such a weapon is suppressed, the sound level
from muzzle gas discharge and bullet flight noise will be many orders of magnitude louder
than the .22 LR. A .22 rimfire bullet is driven with less than a grain of powder, while a
centerfire bullet will use from 25 to 50 grains of powder. The gas discharge at a barrel's
muzzle may only be 800 pounds per square inch (psi) in the case of a .22 LR, while it can
easily exceed 30,000 psi with a centerfire varmint rifle. Bullet flight noise is virtually
the same for supersonic projectiles of the same caliber; whether they are traveling at
1,150 fps or 4,000 fps. In an open field the noise isn't too severe, but near reflective
surfaces like trees and buildings the racket will be substantial. A subsonic suppressed
.22 LR rifle discharge won't be noticed 50 yards away. Suppressed supersonic fire can be
heard up to a mile away on a still evening.
Tactics
A skilful, experienced animal control contractor can perform operations
that absolutely amaze those outside the field. Much of this has to do with knowing the
habits of the animals causing problems. Take, for instance, a herd of deer causing crop
damage in a soybean field, or posing a hazard at an airport. Typically, the needs of
animals are food, water and rest. They will enter and feed in a field close by a resting
area where they feel safe and secure from possible predators. If water is available
nearby, so much the better. The routes they travel to and from their resting areas are
usually very predictable. If a contractor quietly enters from one such area while the
animals are feeding the herd will be disoriented. If the contractor sits down and quietly
dispatches the alpha female with a suppressed .22, the remainder of the herd will continue
to graze, or simply mill around. The confusion and silence will allow the contractor to
quietly take out the bulk of the herd with individual brain stem shots.
Shooting should take place slowly and deliberately, with a suppressed, bolt-action rifle.
Shots should be taken from the side or from the rear of individual animals whenever
possible, with the lower rear portion of the brain the only target. A shot should not be
taken unless one is absolutely sure of his target. Accuracy is always to be preferred over
power. A .22 LR rifle will be adequate at ranges up to 100 yards, as long as the shooter
can place the shot within the brain stem. Although a subsonic .22 bullet has a limited
amount of energy (the short form for energy being 2.2 times the weight in grains to equal
foot pounds at 1,000 fps), velocity does not drop very much over distance when compared
with supersonic bullets, which have four times the drag factor. A velocity of from 650 to
1000 fps is more than adequate for the task.
Aside from distance, bullet drop is probably the most important factor in accurate
shooting. Some contractors use different points on the vertical crosshair for different
ranges, and become very adept at judging distance. There is no substitute for practice
using a paper silhouette of the animal being collected, with the brain stem area
highlighted. Practicing at different ranges will provide a dose of reality for the
optimists who lack skill in field shooting. If this work is not done perfectly the results
can be disastrous in an urban setting. We will not dwell on the problems that could result
from public awareness of a botched shot, but they could be substantial. Shooting at a
paper silhouette can be a humbling experience, but it is excellent and necessary practice.
Improvised field positions should be practiced, with braced sitting and standing with a
rest the most useful. Some shoot from inside a vehicle, using a padded window edge as a
rest, controlling elevation by rolling the window up or down manually. Deer and other
animals near runways in tall grass are sometimes engaged from the top of a pickup truck.
The driver points the truck at the animals at night, while the shooter(s) sit on a board
over the bed, resting their suppressed rifle(s) on canvas pillows filled with sawdust or
styrene beads on the roof of the cab. Again, common sense is called for. This technique
should not be used in full public view, or where planes full of passengers taxi slowly by.
Range Finders
Inexpensive range finders are changing the way some shoot. Bushnell's Yardage Pro series
uses an invisible beam of light to range the distance to a target. The Yardage Pro weighs
18 ounces and has a street price of $180. The more compact 600 weighs 10 ounces and has a
price of $280. The 800 has a weight of 12 ounces and a price of $320. In truth, all will
accurately measure distances up to 1,000 yards on a good day, with a reflective target.
The more expensive units are lighter and will not be as confused by rain, snow or brush.
They are more likely to give a good reading on a small, absorptive target. Sophisticated
operators tape a table of drop and elevation corrections to a rifle's stock for extended
range. Varmints have been successfully engaged at ranges up to 400 yards with the humble
suppressed .22 LR rifle. Deer and feral dogs & hogs have been taken at ranges up to
200 yards with the 48-grain Lapua Scoremax and 60-grain Aguila .22 LR ammo.
Summary
An accurate .22 rimfire rifle with an inexpensive muzzle can is adequate for almost all of
an animal control operator's needs. Ruger 10/22 and 77/22 rifles dominate the industry.
Both have robust actions and easily removable barrels. All rifles are not created equal.
Some are accurate and some are not. If a weapon is not accurate it is the barrel
(thickness, chambering, rifling, muzzle crown, etc.), the bedding, or the suppressor that
is/are at fault. Don't start with an inaccurate weapon as a candidate for suppression. It
won't get any better, and accuracy is of paramount importance. Good looks and price are no
guarantee of accuracy. A symmetrical, catch-free muzzle crown and a symmetrical blast
baffle inside the silencer are very important to long-term, reliable accuracy. While a
barrel doesn't have to be more than six inches long in order to be accurate, it should be
as thick as is practical, since thickness equals strength and stiffness, and both are
important for reliable accuracy in the field. The thicker the barrel is at the muzzle, the
stronger the connection. The muzzle is the last thing a bullet feels on the way out. The
more stable that point of departure is, the more consistently accurate the shot will be.
The most important shot is always the first shot, from a cold bore. This is often referred
to as the cold bore shot, or CBS. Lightweight cans made of aluminum are often fragile.
Serious muzzle cans for animal control work are made of heavy steel or stainless steel,
and they are of large volume in order to handle the abuse and debris that comes from
long-term field usage. While thin barrels can be accurate, a thicker barrel allows more
metal to be used at the joint between barrel and suppressor, and this equates to reliable
accuracy under field conditions.
A semi-automatic rifle offers rapid follow-up shots, but it will be much noisier, and not
as reliable. If the first shot is good, one won't need another one. Many semi-auto rifles
don't start to shoot reliably and accurately until they are warm and running, and that is
often too late for our purposes. The semi-auto can be useful in situations where nests of
rattlesnakes, water moccasins, rats, or similar small targets may be encountered in
numbers. In all other situations a bolt-action rifle with a short, thick barrel, coupled
to a powerful muzzle can will provide quiet, subsonic firepower in a compact package.
Spend enough money on a variable scope and mounting system to get reliable sighting with
adequate resolution. If you can't see it you won't be able to hit it. Adjustable focus on
a side wheel is sometimes quite useful. Brilliant optics are a comfort, but one needn't
demand clarity all the way out to the edge of the field of view, since it isn't necessary.
A variable scope will provide the best image in the middle of its range when there is
little light available. There will be occasional, low-light situations where a peep sight
combined with a hi-visibility front post will be preferred. Paint or tape the weapon with
a camo finish to help it blend in better. A rifle need not be pretty to be effective.
Small and drab is where it's at in this business.
Firing an AR15 with Sound Technology's "M16" can mounted on a 10.5"
upper. "It sounds like a .22 rimfire!" Photo courtesy Chris Halbrook. For more
photos see his suppressor
page.
Practice on a paper silhouette target under simulated field conditions. In the field, get
as close as you can. Thirty to sixty yards are realistic distances. Use a rest or the
braced sitting position whenever possible. Always use ammunition that is subsonic in your
weapon. Don't use hollowpoints on animals larger than 8 pounds. The tip often blows off,
leaving a tiny rear portion with inadequate penetration characteristics. Lapua 48-grain
Scoremax and Aguila 60-grain SSS are solids that will deliver the most effective
performance to the brain stem of a living target. Don't take a frontal shot unless you
absolutely have no other choice. Shots taken from this direction are usually deflected. A
side or rear quartering shot to the medulla oblongata are always to be preferred. While
the lighter 40-grain bullets will work, animals struck with them often shake their heads
and take a step or two before falling down. They usually collapse and expire immediately
when hit properly with the heavier 48 and 60-grain projectiles. If you snap your fingers
once the animal will freeze in position, allowing a still rather than a moving shot.
Grazing animals are almost always moving their heads in rapid and often unpredictable
ways.
Related links:
Chris Halbrook's suppressor
page with photos of Sound Tech suppressors.
Gunwriters' story about Silencer Control
in the United States by Mark White.
Mark White's Sound Technology
website with a regular newsletter
about ammunition development and other current topics.
For more suppressor manufacturers see Gunwriters' Sound Suppressors
links.
Alan C. Paulson's book Silencer History
and Performance, Vol. 1 with a lot of suppressors introduced and measured.
Gunwriters on the Web story about Firearm Suppressors for Wildlife Management: http://guns.connect.fi/gow/wildlife.html