This story by Mark White of Sound Tech
has been previously published in the Small
Arms Review Vol. 1 No 7-9 /1998.
22.02.2000:
The Use of Sound Suppressors on High-Powered Rifles
by Mark White
It should he stated at the outset that the phrase high-powered will cover those
fairly efficient, non-magnum cartridges bracketed between the .223 and the .308 - the
workhorses of the law-enforcement and military community. If one is going to suppress a
sniper rifle, that rifle should he totally dedicated to suppressed fire. Using a rifle
which is only occasionally silenced is an invitation to either a lawsuit or to poor field
shooting, as any rifle will carry a different zero without a suppressor, as opposed to its
zero with one.
A suppressed rifle should be stored and carried in its assembled, ready-to-go
configuration. Many of us have seen movies in which a fitted case full of components
(stock, action, barrel, forearm, scope, mount and silencer) was assembled in the field,
and then used to complete an important assassination. This is pure Hollywood. No
enforcement officer in his right mind would ever assemble a rifle on the spot on a callout
at a crime scene and expect the weapon to hold its zero. It might, but such an occurrence
would be an abnormality. And what would he the moral and legal consequences of a botched
shot in a hostage rescue attempt? By the same token, some suppressors cause shots to stray
with various degrees of tightness or looseness on a rifle's barrel.
The Single-Point Mount
The muzzle and a massive outpouring of high-pressure propellant gas are the last things a
bullet feels before it leaves the control of the shooter. The joint between suppressor and
barrel should be as rigid as that between barrel and action. Often, the suppressor/barrel
interface is conceived as an afterthought. The muzzles of most military barrels are fitted
with small, steel flash hiders, weighing but 57 to 85 g or 2 to 3 ounces. Many
manufacturers try to use the same kind of short, 12.7 mm or 1/2 inch diameter, threaded
muzzle sections to mount suppressors that might weigh up to 1.8 kg or 4 pounds. It may be
convenient to use flash hider threads, but such a tiny joint is very fragile, and lacks
the strength and stability expected of a military or enforcement weapon. A small error in
machined accuracy on a single-point mount can result in a disastrous misalignment problem
near the muzzle of a suppressor.
A suppressor that is held at the rear by a single collet, or by a single section of
threads, is said to be held by a single-point mount. If the threaded section is only 12.7
mm or 1/2-inch in diameter the strength factor is very low. If a heavy target barrel is
used, the threads can be as large as 19 mm or 3/4 to 22 mm or 7/8 inch in diameter. In
this case, the strength and stability factor is much improved. Unfortunately, many
suppressed rifles with single-point mounts suffer from a wandering zero. There is,
however, a better way.
The Two-Point Mount
The two-point mount usually attaches a barrel to its suppressor with threads at the
muzzle, and with a collet, O-ring, or conical joint about 20 to 25 cm or 8 or 10 inches
behind the muzzle. It is a vastly superior way to mount a muzzle can to a rifle barrel.
The resulting joint is many times stronger than any single-point mount could ever be.
Because of the geometry of a two-point mount, a small error in alignment will not progress
into a much larger error at the suppressor's muzzle.
The common configuration has threads at the barrels muzzle, and the step for the rear of
the can near the middle of the barrel. Tightening puts the suppressor in compression, and
the barrel in tension - which we feel is the most conducive to accuracy. Another
configuration has a threaded section in the center of the barrel, where the unthreaded
muzzle stubs or jams into a socket in the middle of the suppressor. We feel that this
configuration (with the barrel in compression) is not as conducive to accuracy, although
it may ease manufacture of the suppressor. However, to our great surprise, we have seen
suppressed .308 systems (with compressed barrels) that appeared to be fairly accurate. Yet
another benefit exists with the two-point mount. Space behind the muzzle exists inside the
rear chamber of the suppressor. That extra volume can be used for more effective
suppression, without adding greatly to the overall length of the weapon in front of the
muzzle.
Barrel Torque
Most rifles have barrels that impart a right-hand spin to their projectiles. Since most
calibers accelerate their bullets to between 762 and 1036 m/s or 2,500 and 3,400 fps, and
since most of this acceleration takes place within the first few inches, there is a sudden
and violent twisting of the barrel in an opposite (left-hand) direction. This torque tends
to cause a barrel held into its action with right hand threads to screw itself ever more
tightly into its action with each shot. One can screw a barrel lightly into an action by
hand. After several shots are fired the barrel will have driven itself tightly into its
action, and it will take quite a bit of force to remove that barrel with a wrench.
That same torque tends to cause a suppressor to loosen if the suppressor is held in place
with right hand threads, which seem to be the norm. One must be constantly vigilant to
make sure that a rifle's suppressor remains tightly screwed in place. Especially before a
critical shot. All Russian and German flash hiders (and some suppressors) are attached
with left hand threads. Those made in the U.S. are usually held on with right hand
threads.
Our testing has indicated that a rifle with a suppressor held in place with a properly
executed, two-point, conical, tensioned barrel mount will remain in zero. This zero
remains even after the suppressor has been removed for cleaning and replaced. As long as
the replacement torque is about the same, the zero will be unaffected. We are talking
about no discernable, cold shot shift after a day, week or year, at 180 m or 200 yards.
Bullet contact with any one baffle in a suppressor usually results in tumbling, with
severe consequences for those baffles that remain downrange of the event. Since the
smallest possible passage hole results in the greatest level of suppression, the pressure
is on to keep internal baffle clearances to a minimum. More than one suppressor (held with
a single-point mount) has been ripped free of its threads, and then violently launched
downrange when baffle contact has caused internal bullet tumbling. Damage to the
suppressor in such an instance is usually substantial. If this happens in the field the
rifle may be undamaged, but it will have to be rezeroed before it can be used effectively.
Moisture Accumulation and Weapon Storage
Water is a major byproduct of gunpowder combustion. A good suppressor will capture and
retain a considerable amount of the liquid. Twenty shots from a .308 will cause about a
teaspoonful of water to be captured. Whenever possible, the weapon should be carried and
stored with the muzzle pointing straight down. The bolt or action should remain open to
allow accumulated water to evaporate and vent. If the suppressor is removed as soon as the
shooting stops, heat in the suppressor will rapidly dry most of the internal components.
Unfortunately, most rifles are traditionally stored muzzle-up. This causes water and
trapped particulates to slowly release, where they will fall and lodge in the chamber area
and bolt face. Burned gunpowder is quite dirty, and the inside of a suppressor is usually
filthy. Cleaning is best accomplished by flushing the can in solvent, draining, and
blowing the unit out with compressed air. One should get in the habit of storing a
suppressed rifle by hanging it, muzzle-down. Even stainless steel components will rust if
trapped water is not allowed to vent. This may result in a suppressor rusted tightly to
its barrel. A bore with rust near its muzzle may lose its accuracy. Corrosion can occur
quickly in a warm, moist environment. This is not an aspect to be ignored.
The Blast Baffle and Its Effect on Accuracy
The most critical moment in a bullet's flight path is just after it exits the barrel,
where the highly elastic and more rapidly moving gasses overtake it and press upon its
base. The first baffle in a suppressor is called, appropriately, the blast baffle. This is
the most critical component in the entire baffle stack. The blast baffle is subject to a
great deal of heat, stress and impact. Many baffles have asymmetrical surfaces, and these
can bounce the blast of high-pressure gas around in a way that disturbs the stability of
an exiting bullet. When we first started experimenting with asymmetrical S, Z and K style
baffles this phenomenon became painfully obvious. Keyholing, tumbling and baffle contact
were common because the bottle-shaped blast of muzzle gas overtook the exiting bullets,
deflected off the asymmetrical surfaces, and then deflected the bullets. Accuracy was not
good. Some manufacturers haven't learned this lesson yet, and their suppressors are
plagued with inherent instability and resultant accuracy problems.
The blast baffle must have a perfectly symmetrical, coaxially aligned surface and bore. It
must be made of fairly tough steel, stainless steel or inconel. If it is made of a soft
material like copper, brass, titanium or aluminum, the high-velocity impact from unburned
grains of powder will peen the surfaces - eventually reducing the size of the bore orifice
to the point where destabilizing bullet contact results.
A properly designed blast baffle will strip and deflect much of the bottle-shaped blast of
high-pressure gas that envelops and pursues the departing bullet. For this reason, one can
logically expect an increase in practical accuracy when a properly designed suppressor has
been installed. Also, the weight of a heavy steel unit tied to both the center and end of
a rifle barrel does beneficial things for harmonic barrel vibration - dampening out much
of it. These two factors greatly increase the practical accuracy potential of a suppressed
rifle. The properly suppressed rifle becomes very stable and reliable. Larger internal
clearances reduce the likelihood of baffle contact in the event that the suppressor or
barrel get slightly damaged or bent.
The Supersonic Crack
Any projectile moving through the air at a velocity greater than the speed of sound (332
to 340 m/s or 1,089 to 1,114 fps in dry, 18 C or 65 degree F air, depending on who one
listens to) will create a supersonic crack. Temperature, humidity and atmospheric pressure
variations play a role in raising or lowering the speed of sound by a small percentage. In
a firearm which lacks a substantial muzzle report (being fired over an open field) the
sound resembles the loud tearing of a bed sheet.
Two sounds are actually created, one from the front of the bullet, and one from the rear.
Near trees and buildings the sound waves come back as a distinct crack or pop each time
the speeding bullet passes some object with a vertical, reflective surface. Once the
muzzle report has been diminished the supersonic boom becomes dominant. Curiously, the
sounds will now appear to come from the target area, rather than the rifleman's position.
Sound moves through our atmosphere at a relatively fixed rate. A sound wave will typically
strike one ear a bit before the other.
The human brain is capable of detecting the difference in time between sound impacting one
ear and then the other in an increment of as little as one/six-millionth of a second. With
time and practice we soon learn to use this ability to pinpoint the source of a sound very
accurately. Because a suppressed muzzle report is relatively quiet, the uninitiated will
automatically home in on the loudest sound, which in this case is a sonic boom reflecting
from the target area. The intense, sharp sound of the bullet's passage will seem much
louder than the muzzle report to someone close to the flight path. Indeed, a rapidly
moving .308 bullet will sound louder than a .22 LR pistol, to someone who is positioned a
few feet from its flight path.
Smaller diameter bullets make less noise than larger diameter bullets. Supersonic is
supersonic. A bullet traveling 366 m/s or 1,200 fps will make about the same noise as one
traveling 1220 m/s or 4,000 fps. Projectiles that are .308 inch in diameter will be
somewhat louder than .223 bullets. There is no technology which can remove the sound of a
supersonic projectile, no matter what claims are made to the contrary.
Above is a nice chart relating to bullet noise and velocity that
is worth looking at. Transonic is between 1,000 fps and 1,300 fps, and the noise
level goes up very, very steeply between those velocities. The noise goes up very
slowly between 700 and 1,000 fps, and then takes a dramatic jump to between 90 dB (which
is virtually nothing) to almost 140 dB (which is major noise) at 1,300 fps. The
noise levels were measured 10 meters to the side of the bullet's flight path. It is
nice to see some serious, authoritative studies done on the subject. Measurements
were taken all the way up to 3,800 fps, where the noise level increased slightly from that
which existed at 1,300 fps.
For measuring this bullet flight sound diagram every .308 cartridge was handloaded prior
to each shot. A T8 Scout suppressor is attached to a BR varmint rifle. Sound meter remote readout and loading
equipment are shown beside the rifle. Contrary to previous belief it was found, that in
practise the speed of sound (Mach 1) was not any sudden threshold to sonic crack. Results
of these as well as of other Suppressor Project
experiments are published in Alan C. Paulson's book Silencer
History and Performance, Vol. 1.
Sound Level and Recoil
Even though the supersonic crack remains, the overall sound level is greatly diminished.
The report sounds like a rapid hiss of compressed air as the slowed gasses issue from the
muzzle of the suppressor. The suppressed .223 and .308 rifles become quite comfortable to
shoot without hearing protection.
Since propellant gas is responsible for about half of a rifle's recoil, and since that gas
is captured and released slowly, the recoil level will be about half that of an
unsuppressed rifle. A .308 has a propellant charge weighing about 50 grains. This is of
course converted to 50 grains of gas, and this gas only moves forward about 60 cm or 2
feet before the suppressor baffles intercept it. The fact that the gas doesn't leave the
muzzle of the suppressor at high speed is responsible for much of the reduction in recoil.
The interception of forward momentum (which results when that gas is captured in the can)
is responsible for much of the remainder of the reduction in felt recoil. In addition, the
weight of the heavy can on the rifle's muzzle acts as a pendulum, limiting muzzle rise and
swing as the rifle recoils, and then pivots around the shooter's body mass.
MUZZLE BRAKES? RECOIL? All brands of Suppressor Project tested
muzzle brakes increased the shooter's exposure by 5 to 10 dB. The increase in noise
exposure is proportional to the recoil reducing effect of the muzzle brake. Replacing it
by even a modest suppressor may thus produce a considerable 20 dB improvement at the
shooter's position. This principle is valid for all weapons equipped with muzzle brake.
Suppressors reduced recoil energy by 20 to 30 per cent, or about as much as muzzle brakes.
They also prevented muzzle climb of assault rifles, firing full-auto bursts or continuous
rapid fire. The page Suppressors and Shooting Range
Structures page tells more about the topic.
We have said all of this about recoil only because many people have a hard time
understanding how 50 grains of gas can he responsible for as much felt recoil as 168
grains of rapidly departing bullet. The answer of course is that the bullet, being heavy
and inelastic, issues forth at a relatively slow speed when compared to the lighter and
(we are told) perfectly elastic gas. Since energy is a product of mass times the square of
velocity, it can be seen that the gas doesn't have to exit many times faster than the
bullet to equal its energy. Empirically, we know that recoil from a suppressed rifle
carrying a high powder charge is much gentler with a suppressor than without. All
theoretical argument stops after that point. If a rifle hurts you to shoot it before
suppression, it becomes quite comfortable to shoot after it's been suppressed.
It should be mentioned that (if a rifle was first sighted in, and then suppressed) the
point of impact will be much lower and a bit to the left for a right-handed shooter. We
need to say that again. The point of impact will not be the same if the previously zeroed
rifle is used with (or without) its suppressor. A rifle simply cannot be zeroed in one
mode and then used in the other. This is a serious liability issue for law enforcement
snipers. Litigation specialists (lawyers) will hammer this point to exhaustion in a
courtroom if a hostage rescue situation ever goes bad as a direct result of a botched
shot, or if innocent bystanders are wrongfully injured.
The rifle, scope and suppressor must be regarded as a unit, and they must remain as a
unit. If a number of suppressed rifles exist in an armory, they must be numbered, and the
respective pieces must remain married, so that suppressors stay with their assigned
rifles. Identical suppressors on identical rifles may be interchangeable without affecting
cold shot zero, but an officer of the law should not take that chance.
Barrel Length and Overall Rifle Length
Most sniper rifles have barrels ranging from 61 to 76 cm or 24 to 30 inches in length. An
effective suppressor needs from 20 to 30 cm or 8 to 12 inches of length in front of the
muzzle in order to function properly. A 1.2 m or 4 foot long rifle can easily become a 1.5
m or 5 foot long rifle with the addition of a muzzle can, and this may be awkward in some
situations. Most suppressed rifles have fairly short barrels in order to reduce the
overall length. Expect to lose about 43 m/s or 140 fps when cutting a 66 cm or 26 inch,
.308 barrel down to 51 cm or 20 inches. As a practical matter, most high-powered rifle
barrels are cut to between 41 and 46 cm or 16 and 18 inches.
We have been taught from grade school that long barrels are much more accurate than short
barrels, but this has no basis in fact. We personally find that an 46 cm or 18 inch barrel
is a bit more accurate than a 66 cm or 26 inch barrel. The chamber, throat, crown and
rifling are more important than barrel length. Subsonic rifle barrels may range from 20 to
30 cm or 8 to 12 inches in length. One does not need very much linear acceleration in
order to reach a velocity of 300 m/s or 1,000 fps with a .308 bullet. Privately owned
rifles in the U.S. must have barrels over 406 mm or 16 inches in length, or they will
require a $200 Federal Tax Stamp and registration in order to remain legal.
A steel suppressor tube can be welded to a short barrel to avoid the tax and the hassle,
as long as the overall length of the unit is beyond 406 mm or 16 inches. Soft solder or
glue is not an acceptable alternative to welding. The intent of the U.S. BATF ruling is
that the assembly must be permanent, and not easily altered. To clear up confusion,
shotgun barrels must be over 457 mm or 18 inches in length. Again, rifle barrels must be
over 406 mm or 16 inches long. This is of no concern to police and military where the
organization or unit (not the individual) actually owns the weapons, although LE agencies
are still required to register these with ATF.
If you have a choice of bullet weight it is useful to know that heavier bullets operate
more efficiently (than light bullets) out of a short barrel. A .223 barrel should have a
178 mm or 1 in 7 inch twist in order to stabilize the heavier 69 and 80 grain bullets. A
.308 barrel (shooting 180 and 200 grain bullets) is best served with a 254 mm or 1 in 10
inch twist. The common 305 mm or 1 in 12 and 356 mm or 1 in 14 inch .308 twists won't
stabilize any .308 bullet much heavier than the industry standard 168 grain, boat-tailed,
hollow point, match projectile. If stability is a problem, round-nosed, flat-based bullets
may be the answer. They are inherently more stable than sharply pointed, boat-tailed
projectiles.
Subsonic bullets are not normally shot in combination with high-powered bullets. Because
of softer recoil characteristics and less muzzle rise, a subsonic .308 can be expected to
strike roughly 36 cm or 14 inches lower than a full-powered load at 90 m or 100 yards.
Again, the issues of cold shot zero and liability raise their ugly heads. During WWII,
subsonic rifle bullets were sometimes loaded and fired backwards in suppressed rifles.
This resulted in an increase in both accuracy and terminal effectiveness.
Tactical users who must use factory ammunition will be best served with the 168 grain,
Limited Penetration (LP) round from Black Hills, unless they are shooting through steel or
glass. The LP round duplicates other match rounds in accuracy and zero, but is designed to
virtually explode upon impact, leaving no large fragments to exit the primary target and
cause secondary injury to other individuals. The standard .308, 168 grain, match round has
proven itself capable of penetrating over 40 layers of 13 mm or 1/2 inch sheetrock after
exiting a primary target, a serious legal liability in the law-enforcement arena.
Suppressor Length, Volume and Profile
Design excellence aside, bigger is usually more effective. Volume can be achieved more
effectively with diameter rather than length, but both are important. High-powered rifles
require an exterior diameter of at least 38 mm or 1-1/2 inches, and a length in front of
the muzzle of at least 18 to 25 cm or 7 to 10 inches. Some of Hartikka's designs dump the
gas into a huge coaxial reservoir behind the muzzle, require only 3 to 5 inches ahead of
the muzzle, and thus reduce overall length considerably. Subsonic rifles often require
maximum suppression. Without a sonic boom it is possible to totally mask an event such as
a gunshot.
Since high-powered projectiles will always generate their own noise, there is little point
in trying for extreme suppression. A good suppressor exists to make shooting comfortable
without hearing protection, and to mask the location of the shooter. Greatly reduced
recoil and an increase in practical accuracy are side benefits.
Public Relations
The traditional visual profile of a muzzle can carries a public relations stigma that goes
back to 1934, and is not easily overcome. It is possible to disguise the profile of a
slender muzzle can by extending the tube all the way back to the receiver. On a
high-powered rifle this adds weight and expensive stock work. To some, the penalty of
money and weight is worth the effort. The diameter of a Remington or Savage action is 35
mm or 1-3/8 inch, which seems to be the inside limit for a rifle suppressor. We had such a
suppressor built (35 mm or 1-3/8 in diameter by 61 cm or 24 inches long) on a Savage .223
varmint rifle with a laminated wood stock. The disguise was extremely effective. A public
relations stigma did not follow this weapon. We took it to firing ranges and gun shows and
brandished it in public. Unlike the typical rifle with a muzzle can, no one appeared
alarmed by its presence.
Experts refused to believe it was anything but a bull-barreled target rifle, even after
being told that it was suppressed. Unfortunately, the slim tube (extending a mere 20 cm or
8 inches in front of the muzzle) did not have the suppression rate that a normal 38 x 305
mm or 1.5 by 12 inch tube would have provided. A larger diameter action would allow a
larger diameter tube to be installed without looking unusual. These actions are available,
but they are more expensive. It is possible to have the tube larger in diameter than the
action, but this looks unusual, thus the disguise is not as effective.
Gunfire noise is the most objectionable sound to the public at large. The louder it is,
the more of a problem it creates in an urban area. A quieter sound is perceived as less
lethal, and is therefore less objectionable. Where rifle fire must be used in an urban
setting by law-enforcement personnel, a suppressor will greatly reduce the PR fallout, as
long as it remains shielded from public view.
Heat Buildup
Typically, the hotter the suppressor gets with a single shot, the more effective it is.
Full-auto fire with a suppressor will dramatically increase cyclic rate. It wilI also
raise barrel temperatures considerably, because the hot gasses are trapped inside for a
longer period of time. Full auto fire is best kept to two or three-shot bursts. As a
general rule we don't expect machine guns to be very effective in a tactical scenario.
Most perps will be behind cover by the third round.
Archive photo: If used with machine guns like this MG34, the interior heat absorbing area of a suppressor should be
minimized instead of maximized to prevent it being damaged from overheating.
We are much more in favor of a single, carefully directed shot. We believe that accurate,
effective, long distance tactical fire is more likely to occur with a bolt action rifle
than with a bullet hose. The commotion associated with most machine guns is much more
likely to draw attention than a single rifle shot, whether the firearms are suppressed or
not.
Suppressor Construction and Materials
The metals most commonly encountered in suppressors are chrome molybdenum (usually 4130)
steel, stainless steels, aluminum and titanium. Chrome moly steel is hard, tough and very
durable. It takes non-reflective surfaces (Parkerizing) and holds paint very well. Paint
is fast becoming the coating of choice, as it is corrosion resistant, and can he changed
(to camo) or easily renewed as situations warrant. Bake-on polymers can be cured in an
oven at 350 degrees F. Some of these coatings are very tough indeed, and serve well in
extended firings.
Aluminum is light in weight (about a third the weight of steel) but it is fragile and
doesn't take knocks, abuse and thread wear very well. Nor does it take heat well. It gets
very soft and then fails and melts near 480 C or 900 degrees F. By contrast, steel won't
melt until it reaches 1480 C or 2,700 degrees F.
Some aluminum cans are anodized, and then dyed black. The anodized coating looks good at
first, but then gets beat-up and chipped. Aluminum does not take or hold paint very well,
even after being sand blasted. Aluminum has a very high heat conductivity. This is a good
property, because it will allow the material to rapidly absorb heat from the burned
propellant gasses, reducing noise in the process. There is an old saying in the suppressor
industry: "Put the fire out quickly, cool the gasses down."
Most aluminum is 6061-T6, which is much cheaper than steel, and moderately easy to
machine, although it is sticky and tends to gall. End caps and baffles are usually
machined out of 2024, which is soft and very easily cut. The alloy 7075 is sometimes used.
It is hard, strong, more expensive, and abrasive to cut. Most aluminum will bend
considerably before it finally breaks. The alloy 7075 cracks before it gives, and is not
weldable The alloys 6061 and 2024 are weldable, but most aluminum cans are threaded and
glued together. When an aluminum can fails it usually does so at the root of a threaded
joint, at the blast area.
The softness of aluminum makes it very prone to wear at contact points, such as the
threaded joint where it is screwed or locked on to a barrel. Gas erosion can be severe in
a high-powered rifle. Aluminum also has a high co-efficient of expansion, and this can
cause problems with zero, or with a rapid loosening of parts. It is so soft that axial
alignment may eventually become a problem as threads get beaten loose and sloppy. Cast
aluminum is very porous and weak, and should not be used.
Stainless steel has nickel and chrome alloyed in with the steel. It is more corrosion
resistant than steel or aluminum. Stainless holds paint poorly, and also has a high
coefficient of expansion. Stainless comes in many grades and hardnesses. The harder grades
can he brittle. The softer grades are subject to thread wear and deformation from
battering. Stainless is expensive and hard to machine. It is not available in the variety
of sizes that one finds with aluminum and steel. Stainless has a fair degree of
conductivity. It is not as reliable as steel. When a stainless can fails it usually does
so along a seam, or at the root of a threaded joint in the blast area.
The commonly used type 304L series of stainless is dead soft, very corrosion resistant,
easy to machine and welds beautifully. Its downfall is that it is easily deformed. If a
can made of 304L is dropped or impacted in shipping or deployment it may easily he
deformed, and this may affect axial alignment. Other commonly used stainless alloys, such
as 316 and 321 tend to he harder and more resilient, but they are also much more difficult
to machine and weld. There are literally hundreds of stainless alloys available, and they
may have very different characteristics. Those used for some rifle barrels have high
percentages of sulfur and lead, which improves machinability while decreasing wearability.
The ideal stainless alloy would possess the ductility, machinability, resilience and
weldability of 4130, chrome moly steel, yet be susceptible to corrosion.
Titanium is about half the weight of steel, has a very poor conductivity, is very
expensive, is highly resistant to corrosion, and is almost as strong as steel. It is very
difficult to machine. It destroys cutting tools because its abrasive nature combines with
its poor conductivity to produce high heat buildup in cutting tools, softening their
edges. Titanium takes and holds paint fairly well. It is about as shiny as stainless, but
is a little darker in color. Titanium's light weight and strength are a plus. Extremely
high cost and poor conductivity are a minus. There are several titanium alloys available,
the most common of which is 3, 2.5 (pronounced three two five), containing 3 % aluminum,
2.5 % vanadium, and 94.5 % titanium, which is used in high-end bicycle frames. The alloy
6A4V90T is sometimes used in receivers and barrels. The bore life of a titanium barrel is
not especially good.
Steel, stainless steel and titanium are very weldable using the TIG (tungsten, inert gas)
process. Aluminum is also weldable, but it takes a high degree of skill and experience to
do so effectively. Only steel and stainless steel are able to be welded to each other in a
meaningful way.
Threading and Alignment
Suppressor manufacturers fall into two camps - Threaders and Welders.
Neither likes the other, and both think that their own methods are vastly superior.
Threading greatly weakens the tube. Welding is strong and permanent, but distorts the
metal. Just as there is a constant and vigorous search for better and more complex
baffles, so too does the controversy between welders and threaders rage.
There is usually a demand for a wide variety of suppressors, so individual manufacturers
stock a variety of parts for different models, most of which have been turned out on CNC
or automatic screw machines, in limited runs. The parts are kept in bins, and usually
consist of a main tube or body (which is the registered, serially numbered part in the
U.S.), a front end cap, a rear end cap, and a baffle stack - which may or may not be
sequentially important.
If the baffle stack is sequential the larger spaces are usually towards the rear, near the
barrel's muzzle, while the smaller spaces are probably in the front. So many cans have
been taken apart by incompetents, and reassembled incorrectly, that the industry trend has
been towards sealed units that can be cleaned by immersion in a solvent. Design rip-offs
are common in the industry, thus welding and sealants are also used to mitigate
intellectual thievery. Baffle design, optimal spacing and proportion are critical to
performance. Patents abound, but they afford little protection in foreign countries.
Often, patent drawings do nothing more than afford competitors baffle designs that they
would otherwise have to purchase and destroy suppressors in order to obtain.
A can with a single-point mount relies on the rear end cap for all of its axial and
angular alignment. The rear end cap was probably made on an automatic screw machine, and
bored and threaded to take a barrel at the same time. It is critical to the alignment
procedure that this was done with extreme accuracy, as a tiny amount of angular or axial
misalignment can result in severe misalignment (and possible baffle contact) in a 25 cm or
10 inch long can.
The best way to bore and thread a rear end cap is to screw and glue (or weld) it into its
suppressor tube first, and then place the entire unit in a lathe for the remainder of the
machining. Few bother to do this, however, because it is much easier to take finished
parts out of bins and assemble them. Line boring and threading in a lathe might mean
having to refinish already completed parts. We have seen a 18 cm or 7 inch long can from a
prominent manufacturer that had 3 degrees of angular misalignment after it was mounted on
its dedicated barrel. This may not sound like much, but try to remember the
sometimes-close tolerances between bullet path and baffles.
If the rear end cap had been welded instead of threaded on, the chances are better that
the unit had been bored and threaded on a lathe after assembly. Welding induces distortion
as the liquid metal cools, solidifies and shrinks, so it is nearly impossible to
successfully thread the bore of a rear end cap before welding. Almost all of the angular
and axial alignment problems we see today are related to a single point mount on a rear
end cap that has been improperly machined prior to being assembled. Again, tubes that have
threaded rear end caps are prone to fatigue and a possible massive failure at the root of
the last inside thread, at the blast chamber. Pressure is low near the front of the can;
thus we rarely see a failure at this point, unless there is baffle contact and bullet
tumbling.
Most two-point mounts have the threaded portion (commonly called "the nut"
or "the spider") located in a more central portion of the suppressor
tube. This threaded portion is very important, as it holds the entire can in place -
usually by pulling it tightly against the rear end cap. There are many methods of holding
the nut in place, and none of them are without their problems: A snap ring may be inserted
in a groove in the center of the tube, but this groove weakens the tube near the blast
chamber. The nut must also be pinned in place, or it will rotate.
The nut can be plug-welded through holes drilled in the tube, but the welding process
slightly distorts (bends) the tube, even if 4 or 6 welds are placed in direct opposition
to each other. The welded or threaded rear end cap can push a thin section of tubing
against the nut, but that nut must still be pinned or glued in place or it will rotate.
Lastly, the nut can be silver soldered or brazed in place, but the area is tough to see
through smoke and fume inside the tube, hence it is difficult to be sure that a proper
bond has been achieved. The soldering process may distort the tube. One must be careful to
boil out the tube in water afterwards, to remove corrosive salts left by the soldering
flux.
The barrel which mates to a suppressor must be turned in a lathe. Threads are best turned
with a cutting tool as the barrel rotates between centers, but I have also seen
satisfactory results obtained with a die-holding fixture in a carriage or tailstock.
Machine threading on a lathe with a single point cutting tool is often called single
pointing, which is not to be confused with a single-point mount. It is felt in the
industry that single point threads are the most accurate. Rolled threads are the
strongest, as they are forged during the process of rolling between two dies.
Few barrels are either straight or symmetrical, and this is another possible source for
angular or axial misalignment. A practiced eye can spot a barrel with a crooked bore. If
the muzzle is clear and open, one can peer down the headstock as the barrel spins in a
lathe to get a good idea about how true the bore is. Short, thick barrels are easier to
deal with than long, thin ones. Barrels which are fluted are often bent during the fluting
process if they are not properly supported and frequently rotated. Fluting has ruined many
otherwise perfectly good barrels. Most fluting is purely decorative in nature, and
normally performs no useful function; no matter what manufacturers claims are made to the
contrary.
Many schemes have been devised to seal a rear end cap where it joins its barrel. A tight
mechanical seal is usually effective, but sometimes rubber or silicone (high heat) O-rings
(or sealants like pipe dope) are used as a backup, in the event that the suppressor
loosens as it is being used. For the sake of reliability and cold shot accuracy, it is
critical that a suppressor not loosen on its barrel.
Cut-away suppressor model for Valmet M62 assault rifle: BR-Tuote suppressors were invented by Finn Juha Hartikka and
are welded together of tough steel. The primary expansion chamber is huge, and
almost 2" in diameter. The gas generated during the firing sequence is dumped
into and trapped within the huge rear chamber, which acts like a reservoir. Here,
the gas lessens in pressure considerably, and slowly leaks out the front, past the compact
baffle stack. The can is a deceptively simple design that has metal only where it is
needed, and not where it isn't. Mounting is typically a two-point system.
A section of small-diameter tube leads back from the muzzle of the weapon. This tube
or pipe eliminates the gas-sealing problem, which we usually solve with a
45-degree cone and carefully machined surfaces, and which leaks if it is not
tight. The tube ties the middle of the can to the rear, making the unit
stronger without adding significant weight. Hartikka's all-steel can is fairly light
and very tough. He calls it a reflex design, as it forces the gas backwards, around
the barrel, thus taking good advantage of wasted space without increasing the overall
length of the weapon significantly. Instead of blasting forward, the gas is trapped
and allowed to bleed off slowly, greatly reducing the noise of the weapon. For more, see
Sound Tech Newsletter. See
also impact shift experiments with suppressed M62.
If a bullet path is not perfectly straight the holes in suppressor baffles will have to be
enlarged to accommodate. Due to angular dispersion, those baffles nearest the muzzle can
have holes which are smaller. We live in a real world, not a theoretical one. Most barrels
have bent bores. Most bores do not lie in the true center of a barrel. Most suppressors
are not perfectly aligned. Threads wear. Welding distorts. That's why we have tolerances,
and sometimes situations require that those tolerances be increased.
Tight baffle holes are more important near the rear, where high-pressure gas exists, than
they are near the front. Asymmetrical baffles usually work best when they line up parallel
to each other. Some manufacturers have a method of holding those baffles in proper
alignment. Some just drop them into a tube and hope that they stay aligned.
Front end caps are either welded in place, or screwed in. If the manufacturer wants to be
able to get back inside the can at a later date he will use a weak glue or ISPBA
(intermediate-strength, proprietary bonding agent - also known as Blue Loctite).
If he wants the end caps to stay, he will use a stronger glue, or HSPBA (higher-strength,
proprietary bonding agent - IE Red Loctite). Aluminum does not glue well, even
with 2-ton psi epoxy. If the can gets hot from rapid use most adhesives will loosen and
eventually fail: Even secret, high-strength proprietary bonding agents will eventually
give up and work loose at the rear end cap, where most of the heat and shock are
concentrated.
Summary
It is difficult to summarize a complex topic in its entirety. Those who use high-powered
sniper rifles have every right to expect those rifles to be dependably accurate. A
properly suppressed rifle must be constructed with a serious commitment to both
suppression and reliable accuracy from the outset. This usually means a steel or stainless
steel silencer mounted to a short, heavy barrel with a robust, two point mount. One can
expect both barrel and silencer to exact a combined penalty of at least 1.8 to 2.3 kg or
four to five pounds in weight, and an extra six inches in overall length.
Continued and diligent practice on a regular basis are vital to a mission. Practice should
he held at night and during inclement weather, as well as on warm, sunny days. Only a few
rounds need be expended, but they should all be accurately and carefully delivered. One
should always look through the bore to ensure that it is clear before a callout or
deployment. Wasps and other insects have a nasty habit of building mud nests in
inconvenient places, and a plug of mud can be disastrous to bullet placement.
Always store the weapon muzzle-down. The suppressed rifle must remain dedicated to
suppressed fire only. To do otherwise compromises cold shot reliability. The benefits of a
suppressed system include a low profile, relative obscurity, increased accuracy, decreased
recoil, greater stability, and a lower likelihood of detection in the field.
Subsonic Knowledge
This article will deal with choosing, loading and using accurate subsonic rifles. Unlike
the more powerful supersonic rifles, whose bullets generate their own supersonic crack,
subsonic rifles are capable of delivering very quiet, almost undetectable, accurate fire.
The sound of a subsonic bullet whizzing through the air at 300 m/s or 1,000 fps is very
quiet indeed, certainly less than an arrow from a bow at 60 m/s or 200 fps.
We won't get heavily into the science of it, but a velocity of 1,000 fps (or roughly 300
meters per second) has long been considered optimal, since well before World War II. Any
slower, and we're leaving precious velocity on the table. Any faster, and one runs the
risk of breaking into the sound barrier (335 m/s or 1,100 fps) in a hot environment, where
gunpowder burns more effectively. A warm barrel or a hot cartridge can easily push
velocity up another 45 m/s or 150 fps even though the cartridge contains a bullet of the
same weight and powder charge.
With a properly designed system, the loudest sound will be that of the bullet strike. With
effective suppressor technology we can all but eliminate the sound of a muzzle blast. By
hovering around 1,000 fps we can virtually eliminate bullet flight noise. The only thing
left is the plop of bullet impact, which can be quite loud on occasion.
Power Level
Subsonic bullets travel much slower than high-powered rifle bullets. Since the formula for
energy squares velocity, it can be seen that the subsonic bullet must try to make up for
the loss of power with mass, clever bullet design and accurate shot placement. One
standard formula divides velocity squared by a factor of 450,400. That, times the bullet
weight in grains, will equal energy in foot pounds. Let's take a 200 grain, .308 bullet
and crunch some numbers. At 2,400 fps that bullet will deliver 2,558 foot pounds of
energy. At 1,000 fps the same slug will only deliver 444 foot pounds of energy.
A 300 grain, .44 Magnum bullet driven at 1,000 fps will delivery 666 foot pounds of
energy. A 55 grain, .223 bullet will develop 1,250 foot pounds of energy at 3,200 fps.
While the energy of a .223 on paper may be twice that of the .44 Magnum, the 44's greater
mass and deeper penetration will prove far more deadly on large animals. In the 1960's the
friends and family of the Ruger empire spent quite a bit of time in Africa with their .44
Magnum, semi-auto carbines. Most who used those .44 carbines were very impressed with
their lethality. The .44 is a lot more effective than the paper ballistics would lead one
to believe. For those who enjoy playing with calculators, a factor of 2.2 times the
proposed bullet weight in grains, will equal foot pounds of energy at a velocity of 1,000
fps.
Barrel Length and Porting
One doesn't need much barrel length to develop a minimal 300 m/s or 1,000 fps of velocity
with a heavy, large caliber bullet. A 20 to 25 cm or 8 to 10 inch tube will provide plenty
of acceleration. For the record, a good 25 cm or 10 inch barrel is fully as accurate as a
much longer one. One more time, with feeling, a 25 cm or 10 inch barrel is fully as
accurate as a 76 cm or 30 inch barrel. We often note a significant increase in accuracy
when we cut a 61 cm or 24 inch barrel back to 25 cm or 10 inches. A proper chamber,
adequate rifling twist rate and a perfect muzzle crown are all more important than barrel
length.
If porting (holes drilled in the barrel to bleed propellant gas) is used as one of the
devices to reduce the noise of a suppressed firearm, it is recommended that the barrel be
from 25 to 30 cm or 10 to 12 inches in length. Porting, when properly executed, can reduce
a suppressor's overall report by as much as 40%. All ports should carry a substantial 45
degree bevel at the bore interface, or they will shave off copper or lead from the
bullets, which will pack up the primary expansion chamber and the ports themselves. If a
suppressor eventually weighs 3.6 kg or 8 pounds more than it used to, there is a good
chance that sharp or burred ports are at fault. Many manufacturers bevel the outside of
each port, but this does little or nothing to cure the problem. Beveling the inside of
each port is not easy, but it must he done.
For private ownership in the U.S., a pistol barrel may be of any length. A rifle barrel
must be over 406 mm or 16 inches long. Any shorter, and a $200 Federal tax stamp (and a
Form 4) will be due on private ownership. Municipality, county or state ownership of a
short barreled rifle or suppressor will of course require federal registration, but no tax
stamp will be due.
Caliber Selection and Bullet Shape
Since velocity is rigidly fixed, the most important area of the selection process will be
based on the assigned role of the firearm. Plinkers and target shooters are well served
with the common .22 LR round. It's cheap, quiet, available and accurate. The high-speed
.22 LR round is transonic, which means that it starts out faster than 335 m/s or 1,100 fps
(supersonic) but then its velocity decays into the area where parts of the bullet are
supersonic, and parts are not.
Aguila's 60-grain subsonic round (named Aquila SSS, for sniper, subsonic) will reliably cycle in Ruger's MK II
512 pistol, and in bolt-action rifles like the 77/22. In most semi-auto rifles we
have found that the short case retracts from the chamber before the firing cycle is
totally completed, causing a loud noise to emanate from the action area. The same
thing occurs with the longer barreled MK II pistols (beyond 5.5").
The slow 1 turn in 16" twist in existing barrels may not always stabilize the heavier
projectiles in colder temperatures. This could result in hunting, tumbling and
keyholing, although we haven't noticed this at warmer temperatures. Accuracy is
fair, but not remarkable. The SSS ammo is very quiet in a suppressed weapon with a muzzle
can. At 80 degrees F we got 790 fps out of a 5" MK II barrel, 850 fps out of a
10" barrel, and about 730 fps out of a 24" barrel.
The stopping power of the slow-moving SSS appears substantially greater than typical
40-grain, .22 LR loads. So far, the round-nosed, flat-based bullet seems to be stable
when penetrating almost any medium. We got 5 to 6" groups at 100 yards with a
factory 77/22 varmint barrel, and ¾" groups with our faster twist barrels. More
on Sound Tech Newsletter.
When a bullet travels through the transonic range the frictional pull trying to slow it
down is from four to five times greater than the pull that exists at subsonic velocity.
Simply put, this differential pull causes instability. A stable, round-nosed, flat-based
bullet (like the .22 LR) will he less accurate in the transonic range. Inherently
unstable, hollow-point, boat-tailed bullets (with the preponderance of mass to the rear)
will lose all stability in the transonic range, tumbling end-over-end and losing any
semblance of accuracy at that speed.
Thirty years ago, those who drove Chrysler vehicles on slippery roads in the northern
states found that, in a situation where control was lost, the vehicle would spin and
settle into a rear end-first attitude, because the rear end was heavier than the front
end. Those who drove Ford products (which typically had less rear-wheel traction on ice)
soon learned that the heavier front end caused the vehicle to be more stable in a spin.
Its natural movement in a minimal traction situation was front-end first. Sharply pointed
bullets have the heaviest end at the rear, and they take a much greater spin rate to keep
them pointed in the right direction. Bullets with blunt points and hollow bases (Like
hollow-based wadcutters) are inherently stable in flight. They fly straight, even without
spin.
In terms of effectiveness on live targets, it is very hard to beat a blunt-nosed or
flat-tipped bullet. Put another way, a subsonic bullet that is a true cylinder will
deliver more shock, hemorrhage and trauma than any other shape. Sharply pointed and
round-nosed projectiles will slip right through, while causing minimal damage. It has been
said that some .30 caliber projectiles are designed to expand at 300 m/s or 1,000 fps, but
this remains to be proven to my satisfaction.
Sharply pointed bullets will penetrate deeply at subsonic velocities - pushing nerve
tissue and blood vessels aside, rather than cutting them. Unless the bullet hits the base
of the brain or a major nerve center, the animal will run away, usually to die a slow and
agonizing death. Most pointed and round-nosed .30 caliber rifle bullets are totally
lacking in knockdown power at subsonic velocities. We hear the same stories of subsonic
.30 caliber bullet inadequacies over and over again, and are frankly quite tired of them.
Subsonic .30 caliber bullets will not expand in large animals. The only effective .30
caliber subsonic bullet will have a totally flat front end.
For those entities involved with animal control, the subsonic .22 LR round is relatively
humane (meaning it kills quickly) and effective on animals weighing up to roughly 20
pounds. On snakes and small vermin the Remington Subsonic, hollow-point round is fairly
effective. It usually stays subsonic, even in long, unported barrels, and is fairly
accurate. On very small rodents a round called the .22 CB Long offers reduced bullet
weight and less penetration. It is not a very accurate round, but works OK for squirrels
in attics and pigeons inside barns at close range. It will sometimes penetrate a sheet
metal roof, so one must be careful regarding a backstop.
On larger, tougher animals CCI's SGB (small game bullet) offers extreme accuracy and deep,
effective penetration. Unlike high-velocity hollowpoints, which often fragment and perform
poorly, the SGB is one of the first modern attempts at scientific design in a rimfire
cartridge. Its bullet is of hardened lead, with a solid, but slightly flattened tip. If I
were going to pack a small .22 rifle into a wilderness survival kit, it would he
accompanied by a large supply of SGBs. They work well on small animals, and work better
than any other .22 LR round on larger animals. Until someone comes up with a .22 LR
wadcutter (I hope CCI is listening) the SGB will remain the most effective .22 rimfire
round available.
The next step up the ladder of higher subsonic energy is the move to a .30 caliber weapon.
The .308 is a logical place to start, and (with a light charge of fast powder) it can he
effective in a weapon that is designed to he both subsonic and supersonic. A 254 mm or 1
in 10 inch twist will stabilize up to a 200 grain, round-nosed, flat-based bullet.
However, the extra room in the .308 case provides a substantial cushion, which can cause
problems with efficiency and consistency. The most ideal situation results when a
cartridge case is just big enough to hold its charge of powder and a bullet, with no room
to spare. In the 1960's a fellow named Joe Apache necked a .223 case up to .30 caliber.
The result was an interesting cartridge called the .30 Apache, which sat ignored for quite
a number of years.
Eventually the use of suppressors burgeoned in the U.S. and Grendel Arms (now known as
Keltec) began experimenting with a similar case in a suppressed M16. The concept
eventually developed into what is now known as the .300 Whisper. That small .30 caliber
cartridge will easily launch a bullet as heavy as 250 grains at a subsonic velocity. Not
surprisingly, the longer, heavier bullets have to be spun at a full turn in 146 to 195 mm
or 6 to 8 inches in order to stabilize at low velocity.
Again, it has been said that some of these heavy bullets will expand at subsonic velocity,
but I've seen absolutely no evidence of it. Indeed, they usually perform like a knitting
needle, poking a small, straight hole, in one side and out the other, wasting 90 percent
of their limited energy beyond the primary target. I've heard the word tumble used in
conjunction with the .300 Whisper, but I've not seen that happen either. The heavy bullets
are capable of extreme penetration, but I have seen absolutely no indication towards
tumbling. Many have had great expectations for the subsonic Whisper cartridge, but until
they develop a flat point for a hard, .30 caliber bullet, I feel that they will continue
to he disappointed.
Dr. Martin Fackler, founder of International Wound Ballistics Association,
devoted a considerable amount of research, study and experimentation to the subject of
subsonic bullets. Based on his own and other research going back 200 years, Dr. Fackler
(in a nutshell) concluded that hollowpoints and expanding bullets are a waste of effort.
One can do no better than to use a simple, hard-cast lead bullet with a totally fiat nose,
and with sharp edges at the transition between the flat face and the cylinder walls. Such
a bullet does not move through the air with the extreme ease of a VLD (very low drag)
bullet, but its terminal effect is considerable.
The next logical step up in caliber is to .338. In the early 1970's, Max Atchisson
of Georgia cut off the shoulder of a .223 case and trimmed it to an overall length of 35.9
mm or 1.412 inches. The result was a case mouth of the perfect size for a .338 bullet.
Called the .338-223 Straight, the cartridge is of great interest. Like the .300
Whisper, it will launch a heavy bullet very quietly. I am told that either of these
efficient bullets will arrive at a target 300 yards distant with a loss of less than 100
fps. Those who are used to supersonic bullets will find this astounding, but one must
remember that it takes a lot of energy to break the sound barrier on a continuous basis. A
subsonic bullet that isn't wobbling in flight is the Honda Civic of the firearms world. It
moves through the air with a velocity decay rate roughly one-fourth the rate of a
supersonic bullet. Until we get a flat-nosed .338 bullet, this cartridge will also suffer
from the same knitting needle-like effect.
We could stop to visit with the .38, but I'm going to bypass that and settle on the .44,
which is really .43 (actually .429) caliber. Ruger now makes a lever-action and a
bolt-action rifle, both of which are chambered in the powerful .44 Magnum cartridge. We've
been waiting for twenty years for these rifles, and are immensely pleased that they are
finally on the market. Wadcutters and flat-nosed, cast bullets are available in weights
from 185 to 300 grains. For those who hand cast, the weights range from 80 to 362 grains.
Since factory ammunition is usually too fast, the subsonic .44 Magnum rifle is a
handloading proposition. Fortunately, Mike Dillon's Square Deal press is affordable, and
cranks satisfactory rounds out at a prodigious rate. The twist in Ruger's .44 barrel is
508 mm or 1 turn in 20 inches, which seems to stabilize 300 grain bullets effectively. It
should be mentioned that, while barrel leading can be a problem with lead bullets driven
beyond 426 m/s or 1,400 fps, it will not be a problem with lubricated, hard-cast bullets
driven to 300 m/s or 1,000 fps. We should also mention that we've been buying plain-based,
hard-cast, lubricated lead bullets from Brownells, and that we shoot them backwards in
order to get the maximum effect.
Midway, Dillon and quite a number of other suppliers sell swaged or cast lead, lubricated
bullets for both the .44 and the .45. We don't care about ballistic coefficient nearly as
much as we care about terminal performance, which has been rated as nothing short of
excellent by contractors, animal control officers and park rangers. The flat-nosed .44
delivers a mighty whack. It has excellent knockdown power. It isn't a good 300 yard/meter
weapon, but remember, we're talking subsonic here. Any bullet that moves at a sedate 300
m/s or 1,000 fps will have a rainbow-like trajectory much beyond 100 yards. Little
velocity is lost, and the weapon is still very accurate at extreme range, but finding the
proper elevation adjustment can be tricky.
The powders of choice have been the time-honored Unique and a powder made in Finland by Vihtavuori Oy called N 310. The
Germans developed a very fast powder for their suppressed rifles during World War II, and
this may be a very close duplicate of that powder. It should be mentioned that the Finns
turned some of their subsonic rifle bullets backwards for better accuracy and improved
terminal performance. They also developed a system using a few drops of solvent to
dissolve the upper layer of their fast powder. After this solvent evaporated, the powder
was thus sealed into the rear of large-volume cartridge cases. A bullet was then seated
and heavily crimped in place. This helped to achieve better combustion and improved
uniformity. Prior to this a filler, such as nitrated cotton fiber or kapok, had been used
on large-volume shells. The solvent was a stroke of genius because it rapidly evaporated,
did the job very effectively, and left nothing extra inside their suppressors.
Interestingly, we were using N 310 powder in a Thompson Contender, which
developed the disconcerting habit of opening up by itself each time it was fired.
Curiously, no damage occurred, and the bullets hit the target as though nothing was amiss.
The standard pistol primers did not indicate any sign of high pressure. The velocity was
300 m/s or 1,000 fps, out of a 21 inch, unported barrel. After this happened several times
in a row we switched to Unique (a slower powder) and the problem went away.
H & R and NEF also make a single-shot, break-open carbine, chambered
in either .44 Magnum or .45-70. These rifles are more robust than the Thompson Contender,
and remain closed when fired, regardless of the load. At a mere $150, these are the
cheapest games in town. Don't think that inexpensive means unreliable or inaccurate. These
are very reliable, accurate weapons. More so than the expensive and finicky Contender.
Dating back to 1873, the .45 Colt is a close cousin to the .44. This rimmed cartridge
offers 10% greater frontal area. The caliber and the cartridge were the end product of a
lot of cut-and-try research. The .45 Colt may be old, but it certainly isn't obsolete.
Many who hunt deer with a revolver feel that the .45 Colt is as close to perfection as one
can get. We really like the cartridge, but are having a hard time finding rifles we like
with the .45 Colt chambering. Winchester and Marlin both make lever-action rifles, but the
feed tube is tied to the barrel and gets in the way of the suppressor. We've been buying
.45 Colt barrels with a 356 mm or 1 in 14 inch twist from Bullberry in Utah for the single
shot Thompson Contender. We look forward to the day when H & R, RUGER and NEF make
their rifles in .45 Colt.
The .45-70 cartridge seems like an obvious step beyond the .45 Colt. We've suppressed this
round but are not as happy with it as we are with the .45 Colt. The Colt has a slug with a
.451 inch diameter and is available with bullet weights up to 425 grains. As a cartridge,
the Colt is compact and easily loaded. Its case walls are heavy and durable. The current
popularity of cowboy action shooting make the .45 Colt cartridges readily available, and
inexpensive. The .45-70 has a bit more capacity than we really like, and its case walls
are quite thin near the mouth. The mouth is easily bent or deformed. We've crumpled and
ruined quite a number of .45-70 cases while attempting to resize or seat bullets. The
diameter of the .45-70 is .458 inches. Cast bullets are available in weights up to 645
grains, which ought to be plenty for almost any situation we can envision in North
America.
Some have attempted to suppress the mighty .458 Winchester Magnum. That is truly a waste
of effort, as there is absolutely no difference between the subsonic .458 and the subsonic
.45-70, other than that the .45-70 is more efficient because its case capacity is smaller.
We're not saying no to either the .45-70 or the .458, it's just that we like the .45 Colt
a lot more. The .44 Magnum and the .45 Colt suppressed rifles are perfectly suited to the
task of quietly harvesting or removing animals weighing between 100 and 600 pounds. Both
cartridges are supremely accurate and very efficient at subsonic velocities. The ideal
weight of bullet will drive completely through the animal in question, remaining just
under the skin on the far side. This is a close to perfection as it gets. The .44 Magnum
and the .45 Colt have excellent knockdown power when loaded with bullets having absolutely
flat front ends.
The only possible improvement over the .44 and the .45 Colt would be a move to the legal
maximum diameter in the U.S., which would be .50 caliber. Interestingly, the French were
among the first to do this in the 1870's, when they fitted one of the first metallic
silencers to a .50 caliber Remington Rolling Block pistol. The.50 Remington (M71 Army)
used black powder to drive a 300 grain lead bullet along at a sedate 183 m/s or 600 fps.
The powder was corrosive, and the suppressor would have to be boiled out with soap and
water, and then oiled after use, or it would eventually be destroyed by corrosion. Rimmed
.50 caliber cartridges can be made from 50-70 brass, an expensive and laborious tasks. A
wadcutter bullet would have to he designed in .50 as this is not an item which is readily
available. The .50 caliber offers almost 20% greater frontal area over the .45. A bullet
weighing between 400 and 1,000 grains would seem appropriate for this caliber. Again, we
have been very happy with the .44 and the .45 Colt, and find a need for anything beyond
these two cartridges unlikely.
Mark's large caliber rifle suppressors are described on his Sound Tech website.
Related links:
Gunwriters' stories about Silencer Control
in the United States and Suppressors for Wildlife Management
by Mark White. Gunwriters' Kickback discussion about Aguila's 60-grain subsonic round Aquila SSS.
Mark White's Sound Technology
website with a regular newsletter.
For more suppressor manufacturers see Gunwriters' Sound Suppressors
links.
Suppressor Project page. Suppressors and Shooting Range Structures. Bullet flight noise. Bullet impact shift with M62 suppressors and flash
hider. Directional noise diagram of
suppressed M62. Suppressed 308 Rifles measuring
data.
Alan C. Paulson's book Silencer History
and Performance, Vol. 1, the basic suppressor book.
U.S. Suppliers:
Brownells, mc., 200 S. Front St., Montezuma, Iowa 50171. Phone: 515-623-5401, Fax
515-623-3896
Bullberry, 2430 W. 230 N. 67-5 Hurrican, Utah 84737. Phone: 801-635-9866
Dillon Precision Products, 8009 E. Dillon's Way, Scottsdale, AZ 85260-9865 Phone:
800-223-4570, Fax 602-998-2786
Midway, Box 718, Columbia, MO 65205. Phone: 800-243-3220, Fax 573-446-1018
NEI Handtools, a supplier of custom bullet molds, 51583 Columbia River High-way,
Scappoose, OR 97056. Phone: 503-543-6776, Fax 7865
Gunwriters on the Web story about Sound Suppressors on High-Powered Rifles: http://guns.connect.fi/gow/highpow.html