9mm & .40 cal Wet Cans



The models in current production are a robust 1.25-inch diameter, by 5, 6, 7 or 8 – inches in length, with weights of 5, 8, 11 & 14 ounces.  The blast baffle, shell and end caps are of 4130, chrome moly steel, welded in place.  Spacers and perforated S baffles are of aluminum, to save weight.  The primary expansion chamber, S baffles and spacers are striated to enhance retention of water coolant.  Water is fairly clean, convenient and probably the most effective.  Other ablative materials are shaving cream, shaving gel, KY Jelly, Vasolene, butter, lard, grease and oil.  Some of these can be introduced into the primary expansion chamber and into the other chambers with a large syringe.  Water is the most available material, and since it has the highest specific heat, it tends to be the most effective.  There are times when one wants to load up a can days or weeks ahead of an anticipated event, and for this situation the material of choice seems to be white or yellow wheel bearing grease.  This lubricant won't drain out before the event, and can handle high temperatures.  It works well to silence a report, however, must be applied with moderation to prevent obstructing the bore of the suppressor.  Too much will cause bullets to strike baffles, which can damage the can and deflect from point of aim.

Our first wet suppressor was built on request from a military unit, as an attachment to the military issue 9mm Beretta, for use with 147, 158 & 200 grain, subsonic ammunition.  When used dry, the shorter suppressors operate with mediocre performance, but don't require ear protection.  When a half-ounce of water is introduced into the rear chamber the longer 7 & 8-inch units operate with almost undetectable silence.  The use of a suppressed system with supersonic, 115 to 129-grain ammunition defeats the purpose, as a loud ballistic crack will announce to all that a shot has been fired.

          The factory barrel must be replaced with a longer, threaded barrel in order to allow attachment via industry standard ˝-28 threads.  Some vendors are putting out barrels with improper chambers, crooked, sloppy threads with a flat milled under the barrel, and inadequate shoulders.  Proper alignment and thread fit should always be checked after a new barrel has been installed.  In general, barrels from Fire Dragon have been satisfactory.  Barrels from Federal have not.  A number of outfits make and sell aftermarket barrels.  We will add approved vendors as they come to light.

          Alignment of a barrel with a can may or may not be a problem, depending on the quality of the barrel, and especially on the quality of the threaded portion and its shoulder.  We weld our rear end cap in first, anneal and normalize, and then centerdrill, bore and thread while the can is spinning in the lathe.  Runout will be less than .003-inch, and it will be parallel (not angular) runout.  A typical joint relies on threads to pull the barrel back and to hold it in place, and a shoulder to seat against.  Traditional rifling styles are right-handed.  When combined with right-handed barrel threads the end result is a tendency to twist the barrel back out of the can, in reaction to spinning a bullet.  Since left-handed threads are not catching on, one must be continually attentive to the tightness of the can on the barrel, to ensure that the rear is always snugly up against the shoulder of the barrel.  Overtightening is not the answer, as most self-loading pistol barrels have very thin walls, which doesn't leave very much material for both threads and a shoulder.  It is possible to literally twist the end of such a thin barrel off, so be careful!  If there is a doubt about proper alignment, simply clamp the barrel in the three-jawed chuck in a lathe, install the can on the end, and turn the lathe on.  If the joint is proper the can will spin smoothly.  If the threads or shoulder are messed up (on either barrel or can) a wobble will be plainly evident.  Threads are normally a little sloppy.  The shoulder on the barrel holds the can in proper angular alignment.

Our 9mm and .40 S&W cans do not use a recoil booster, yet they allow the 9mm Beretta (if clean and properly lubricated) and Taurus clones to cycle reliably with a 9-pound replacement recoil spring.  When used with a factory-standard, 16-pound recoil spring and longer, heavier cans, the suppressed weapon must be cycled by hand.  Glock pistols (while very reliable in the normal, unsuppressed mode) have difficulty cycling with the added weight of a can on the ends of their tilting barrels.  They should be viewed as hand-cycled, repeating firearms when suppressed.  This is not necessarily a disadvantage, since a hand cycled weapon will be much quieter than one that cycles automatically.  In addition, spent cartridge casings are much easier to capture in this mode, leaving less evidence on the scene to be policed up and dealt with.  A properly suppressed weapon that must be cycled by hand offers total elimination of flash, as water in the can effectively quenches the spent propellant and flaming gasses.  The concern about shooting in an explosive environment is somewhat mitigated if proper ammunition is used in a wet can, and if shots are directed with care.  A weapon that cycles by itself will eject glowing particulates from the breech. This may easily be ascertained when shooting in a darkened environment.

Using a pistol without a can, and with a lighter recoil spring, may very likely crack the slide or frame of the weapon, as self-loading pistols and their operating springs are very carefully tailored to loads and reciprocating mass.  When a pistol is used without a can the heavier factory spring should be reinstalled.  In fact, swapping barrels and springs is so easy on Beretta and Taurus pistols that the shorter factory barrel should be installed as well as the heavier spring, when shooting unsuppressed.

It should be mentioned that most cans over an inch in diameter occlude (cover up) the front sights and also lasers mounted in guide rods beneath barrels.  A clamp-on laser beneath the frame works well, especially with NV goggles. Practice will allow one to get fairly good at aiming a pistol with sights that are obstructed by a suppressor.  Some barrels made for Beretta, Taurus and Glock are so short that the guide rod strikes the rear of the can, preventing cycling.  We would hope that the barrel manufacturer would be able to deal with this problem by making the barrel longer before it is sent out, but such is not always the case.  We can build a can with an extension on the rear to clear the operating rod IF WE KNOW BEFOREHAND.  Note that it is not any easier to extend a can after manufacture than it is to lengthen a barrel after manufacture.  Let us know beforehand if you desire a can with a rear extension.  Our cans are made of welded steel or welded titanium.  Modifications are not easily performed on a finished product.  Also, if you want a can that will operate on both .40 and 9mm, let us know beforehand!  A 9mm bullet will easily go through a .40 caliber can, but a .40 caliber bullet will not go through a 9mm can.  A dual caliber can won't be as efficient, but the difference is not significant with a wet can.

The easiest way to introduce water into a suppressor is by squirting a small amount through the weapon's chamber (or directly  into the rear of the can) with a plastic squeeze bottle (or a canteen) prior to an event.  In the field this can sometimes be accomplished with a quick dip in a puddle or stream.  The cross-cut striations inside the rear of the can hold enough water for from 4 to 7 shots, depending on conditions, after which the 9mm can increases in loudness until all the water is exhausted.  Wheel bearing grease can be applied well before an event, however it is messier to deal with than water.  The 5-inch can is surprisingly effective for a unit so small in bulk, and most pistols will cycle with this unit.  As the cans increase in length, they also increase in overall efficiency.  A 6-inch can is fairly effective, while a 7-inch can is very effective.  The 8-inch steel can is extremely quiet when used with water, but it is the most likely to cause cycling malfunctions because of its weight and length.

          Sound Tech is currently developing titanium versions of the 5, 6 & 7-inch, 9mm & .40 caliber cans, with anticipated weights of 5, 6 & 7 ounces.  The shorter units will enhance cycling reliability with a weapon that is dirty or poorly lubricated.  We also plan to have a can in .45 ACP in the near future.  Expect to pay a heavy premium for titanium because it is extremely expensive and difficult to machine.



Suppressed Pistol Comments by Mark White of Sound Technology




            Silencers are primarily used on firearms for hearing protection.  Some people enjoy shooting, while others must shoot for a living, as a part of their job.  In either case, a silencer on a pistol stifles the sound at its source, therefore it is far more effective as a protective device for hearing than a pile of earmuffs.  Law enforcement personnel often use silenced pistols or short rifles when they enter buildings and trailers.  If a shot has to be fired within a building the report will not cause either temporary or permanent hearing damage.  The ability to hear the movement of suspects inside a building during a search, after a shot has been fired, is very important.  The loudness of just a single gunshot within a room will virtually destroy one’s ability to hear and comprehend verbal commands for several hours.  Police and military operators need the ability to preserve command and control, and silencers on firearms allow that ability to be perpetuated.  The report from just a single gunshot can cause irreparable hearing damage.  While silencers (also called suppressors or cans) have been around since the early 1900s, they are just coming into their own as useful accessories for pistols and other firearms.  In the United States silencers are federally controlled devices, although they can be lawfully owned by private citizens in 35 of the 50 states.  Silencers can also be used by police, municipalities, governmental agencies and military organizations in any state.

The Glock family of pistols is among the most reliable of modern handguns.  The only weapon that surpasses the Glock in this area is the John Browning/Colt/Walther-inspired Makarov in .380, which has both a fixed barrel and a double action.  Browning designed the original pistol after discovering that brass pistol cases would temporarily stick to chamber walls due to internal pressure, and after the pressures dropped somewhat, the remaining amount of energy could be used to eject the spent casing, cock a hammer and insert a new round.  Browning’s breakthrough design began to be manufactured by Colt in 1908.  Walther later copied it as the PPK during WW II, for use by selected officers in the German Luftwaffe.  The Russians took Walther’s pistol after the invasion of Germany at the end of WW II and turned it into the Makarov.  While the end result may have looked crude, it was made stronger, more durable and more reliable than its predecessors, things that the Russians are noted for.  The fixed barrel in the Makarov, combined with an extremely heavy operating spring in the blow-back-action, virtually guarantees proper, reliable cycling.  The barrel remains rigidly fixed in position, allowing flawless feeding from the single column magazine regardless of how varying external forces act on the barrel.  If the ammunition is strong enough to cock the hammer and cycle the non-locking slide when fired, there will be no cycling problems in the Makarov.  The Makarov’s double action allows a rapid second or third attempt at primer ignition in the event of a misfire – an important feature that the Glock lacks.  I mention the aging, but well-designed Makarov because it has four features (a fixed barrel, a very powerful operating spring, a blowback action, and a double action trigger that can drop a hammer again quickly in the event of a misfire) that Glocks don’t.  These features are extremely important to proper cycling with any suppressed, self-loading pistol.

A pocket pistol with a blow-back method of operation is unfortunately only effective with cartridges of limited power, the most common of which are the .22 rimfire (40-grains at 1000 fps), .32 auto (71-grains @ 900 fps) and .380 (90-grains @ 1000 fps).  Cartridges of greater power (9mm through .45 ACP) tend to require operating springs of inordinate strength, and even then they will beat their slides and frames up.  The Russians initially beefed their Makarov round up to 94-grains @ 1100 fps.  They later increased the round to 106-grains @ 1100 fps when they found that it wasn’t performing on individuals that wore body armor.  A blowback pocket pistol of greater power (like the 9mm Parabellum, 115-grains @ 1200 fps) has been the unattainable Holy Grail of firearm designers for many years.  Power levels substantially greater than .380 tend to require pistols with locked breeches, and these must be very finely tuned in order to use a much smaller amount of residual power, delivered at a much later stage in the firing cycle.  While a recoil-operated pistol with a locked breech can be made to handle very powerful cartridges, the nature of recoil-operated, locked breech designs means that alterations (the addition of weight in the form of a suppressor) will cause a number of problems to be visited upon the host pistol.

While Glock has done well with pistols carrying barrels that weigh about four ounces, the situation becomes far more complex when a firearm sound suppressor enters the picture.  Since a suppressor must be attached to the weapon’s barrel, it can easily double or quadruple the weight and destroy the balance of that barrel.  Since a weapon should cycle properly with or without that added weight, it is possible to enter a situation where, if the weapon is arranged so that it will cycle with the weight, the stronger, more vigorous, recoil-operated power impulse will cause damage to the barrel, slide and frame when that inhibiting weight is removed.  The cleanest way to have a pistol work well in both modes is to have a blowback weapon with a fixed barrel.  So, now we’re back to .22 LR, .32 auto and .380.  Glock makes a .380 pistol, but it  is for some reason not available in the U.S.  And even if it were, the .380 is a marginal performer.  Why Glock has never made a .22 rimfire pistol is a mystery.  They could certainly design a good one that would sell extremely well.

On another tack, the Russians were selling a lot of pistols in the U.S., but that was eventually brought to a halt by the Clinton Administration.  With regard to the Makarov, the original .380 round is called the 9 x 17mm, while the supersonic Makarov improvement was called the 9x18mm, as the case was slightly longer.  Since the Makarov barrel has to be changed to a longer, threaded version for suppression, it has been a simple matter to change the caliber to the subsonic .380 simply by purchasing and installing a different barrel.  The blowback weapon works perfectly with either round.  The Makarov pistol was eventually modified to handle the upgraded, more powerful 9x18mm Makarov round and the even more powerful 9x19mm Luger round.  Certain areas were slightly beefed up, and the chambers of the weapons were fluted with shallow, spiral grooves.  The brass or steel of each case was thus forced into the shallow depressions during firing, and this retarded extraction to the point where the smaller, simpler, blowback action accommodated the more powerful round.  These Makarovs haven’t been allowed into the U.S. either, although that could possibly change in the future.  Glock could take this approach with special, heavily-built, fixed-barreled, blowback pistols designed to be suppressed.  Whether they do this or not remains to be seen, although it is doubtful that they will.  The technology is finally in place, and it is possible that a blowback system could also be made to work in .40 S&W.


Pistols Designed for Suppression, and the Concept of Retro-Fix


            Very few pistols are designed from the ground up to be suppressed.  H&K made a stab at it with the oversized MK 23, and actually won a contract from the U.S. government. But their efforts have moving barrels that are so sensitive that they have to use a recoil- enhancing (Neilsen) device grafted onto the rear end of a government-contract-supplied .45 caliber suppressor. Recoil enhancers (or boosters) are short pistons with short springs that use propellant gas to accentuate the movement of a barrel so that it will unlock more easily from its slide during recoil.  Suppressors that have recoil boosters are called boostered cans in the trade.  While they are sometimes the only answer to pistol cycling, they have their own problems, adding length, weight, bulk, slop and infirmity to a system that already makes most handguns awkward.  In addition to that, they represent potential alignment problems, because they add at least three more pieces that have to be built and joined with axial concentricity in mind.  When they are new and freshly greased they work fairly well, although they do add weight and length.  When they get old and corroded they stick, and that causes weapon malfunction.  When they are used underwater the salt, sand and grit cause additional problems.  When boosters get worn and used up they could allow an attached suppressor to droop, and that will result in bullets striking baffles.  Most cans are built with baffles that have less than 20/1000ths of an inch clearance on each side of departing bullets.  This is usually sufficient at a point very close to the barrel’s muzzle, but the potential for a glancing blow worsens as a bullet traverses the length of a can.  I call this potential path the cone of dispersion, as it increases in diameter after it leaves the barrel’s muzzle.  Some cans allow 40 to 50/1000ths of an inch on each side at a can’s muzzle.  At best, a baffle contact causes inaccuracy and bullet tumbling.  At worst it will result in bullet impact inside the can, and that usually rips the can from its threads or coupling and sends it loudly flying off in an unknown direction. 

While we are on the subject of cycling, a self-loading pistol that cycles completely when fired will be inherently louder than one that is hand cycled.  This is because a suppressor will capture and hold gas, allowing pressure to issue from the opened breech area of the weapon before a new round has been inserted.  Not only does filth and corruption enter the weapon’s action, noise issues forth from both ends, and the sound coming out of the back of a cycling weapon is usually louder than that coming from the muzzle of the can.  When discharged at night, fire can often be seen coming out of both ends of most suppressed semiautomatic weapons. 


Threads, Hand, Shoulders, Axial Alignment and Baffle Strike


On the H&K MK 23 pistol, the barrel appears to have been designed as an afterthought, containing a very thin muzzle section and extremely fine, RH threads.  After all the money that was spent on government contracts for that pistol, it turned out that the locked breech was too tight and too complex.  The weapons jammed with sand and grit and wouldn’t function when they came through surf zones on beach insertions, so they aren’t currently being used. The older H&K pistol, designated the P9S, had a fixed barrel and contained a small but efficient gas operating system, but it was apparently dropped from consideration before the government contract was let.  The P9S apparently works reliably in foul conditions, but has been out of production for a number of years.  A simple blowback design based on the original Browning principle, like a scaled up and refined Makarov, would probably work in all conditions.  Grant and design money would have been better spent on that simpler system, but our government officials are apparently fascinated with complexity.  We can’t wait to see the new pistol designs with global positioning, red (don’t shoot) and green (headquarter approval – shoot) lights and interlocks, with shot-counting LEDs and a TV camera built into the handgrips.  Think that won’t happen?  Think again. 

While we’re on the subject, most pistols have barrels that spin their projectiles in a right-hand direction.  Although it happens so quickly that few notice it, this imparts a rapid left-hand twist to the weapon each time it is fired.  The twist throws the pistol’s handle into the palm for a right-handed shooter, but tries to move it out of the hand for left-handed shooters.  Indeed, with very powerful cartridges, some left-handed shooters have actually had weapons come out of their hands upon firing.  A suppressor mounted to a barrel with right-handed threads will tend to loosen during firing, and the operator must be very attentive to this, since a can will droop as it loosens.  H&K came up with a smaller version of the MK 23, called the USP Tactical, available in .40 & .45.  It has tiny threads on the muzzle as well, but at least they are left-handed.  As a general rule, the direction of threads on a barrel’s muzzle should always oppose the direction of rifling in order to maintain tightness during discharge.

  In most cases threads on a barrel do not provide axial alignment.  They merely pull the rear of a can backwards and hold it in place.  Axial alignment is provided by a shoulder on the rear of the threads.  An analogy is to stand erect with a six-foot tall cardboard tube over one’s head.  If the tube fits tight around the head it will still be hard to balance the tube.  If a larger diameter tube sits on one’s shoulders it be more likely to remain in balance.  The analogy is flawed because forward and back have to be considered in addition to right and left, but hopefully the point has been made.  A shoulder on a barrel is so named because it slightly resembles human shoulders, with the threaded potion resembling the human head.  It is the only hope for proper alignment of a suppressor to a barrel, so it had better be right.  The same can be said for the rear surface of a suppressor.  Screw threads provide a very powerful mechanical advantage, and they will align the rear of a can to a proper shoulder on the muzzle of a barrel.

Some cans have their rear end caps welded in place on a tubular body, while others are threaded.  While either system works, it will always be best if the rear of the can is bored and threaded after it has been fixed into position.  A correspondent tested quite a number of suppressed pistols by firing them into the deep end of a swimming pool and collecting the spent bullets.  Marks on the bullets indicated that most were striking baffles on the way out.           

Suppressors are often made from aluminum (which is one-third the weight of steel) where weight is a consideration.  While aluminum is easily machined and light in weight, it is also very soft and easily damaged.  If a suppressor is made of aluminum, the rear end cap will often have a steel or stainless steel insert and a steel blast baffle.  Aluminum threads do not hold up to wear very well, and aluminum blast baffles suffer from peaning by unburnt powder particles.  The peaning will eventually close up the hole in an aluminum blast baffle to the point where bullet contact occurs. An all-steel suppressor may weigh three times more than an aluminum one, but it will be much more robust.  The time-honored steel of choice is 4130, chrome moly. While this steel does rust it is nevertheless quite strong, welds well, and is extremely resistant to fatigue.  Chrome moly is the standard of the aircraft and firearm industry.  Stainless steel may not rust as easily, but cans made of that material are prone to rupture at the longitudinal seam in the suppressor body.  Barrels that are not unusually thick should be made of chrome moly, as stainless steel will bulge or burst.  Stainless is prone to fatigue, is harder to work, and much more expensive.  We have seen quite a number of stainless cans fail during use, bursting and then tearing down a seam.  A solid baffle strike in an aluminum suppressor will be a catastrophic occurrence, while one in a  steel can may not cause any damage at all.


Suppressibility and Reliability


            While the Glock is the pistol I would most want to carry in battle because of its light weight and reliability, there are characteristics inherent in the Glock family that do not make them ideal candidates for sound suppression.  As we move from the.22s, .32s and .380s, and go up the ladder of power to locked breech pistols in 9mm, .40 S&W and .45 ACP, we find that Glocks are the most reliable pistols on the planet.  The designers at Glock started from ground zero and produced a weapon with cycling characteristics that approach perfection.  The Glock pistol is relatively light, yet extremely tough.  It will take an incredible amount of abuse and neglect while still performing effectively.  The story of a Glock salesman doing a law enforcement demo by dragging a pistol down a gravel road on a cord behind his car for a mile or two is true.  When he was done the sights were gone and the slide and the rear of the grip had suffered an amazing amount of damage.  He trimmed some of the frazzled plastic grip area back with a borrowed knife, inserted a full magazine, and fired all of the rounds, one after the other.  The weapon no longer looked very much like a pistol, but it continued to perform reliably. 

            My personal carry pistol is a Glock 23 in .40 S&W.  I’ve used it hard for over ten years, and aside from several easily-cleared misfires, it has never let me down.  It should be remembered that the .40 was developed in the United States as an attempt to improve on the .38 special and 9mm, after a very embarrassing and well-publicized moment suffered by the FBI.  A lot of contemporary thinking and expertise went into the design of what is now the .40 S&W cartridge.  Even though the .40 may have a power level slightly below that of the .45 ACP, tabulated results from actual shootings over the last 10 years show that the .40 S&W, with JHP bullets,  has had more effective results (a higher percentage of stops and fatalities) than any of the other popular pistol cartridges.  While we won’t conjecture or labor on about why this may be so, we will again point to statistics that say that the .40 S&W appears to be working more effectively than any other contemporary pistol cartridge on the street.  The .40 S&W apparently combines power level and magazine capacity in a proper mix with penetration and controllability.

            Effective suppression rates vary both with caliber and with the length and volume of the suppressors used.  Not surprisingly, the larger diameter cartridges are significantly louder than smaller diameter cartridges, when suppressed.  That is to say, a .22 rimfire suppressor will be the most silent.  A 9mm suppressed system will typically be quieter than a .40 S&W suppressed system.  And all of these will be notably quieter than a .45 ACP suppressed system.  The outside diameter of the suppressor body also is important, but there is a point of diminishing returns.  Suppressors measuring between 1.25 and 1.4 inches in diameter appear to be most effective.  Simply stated, the larger the borehole through a suppressor, the greater the sound level that will issue forth.  While internal ballistics and cartridge design can get very complex, this one simple fact continues to stare us in the face.

Whenever one uses suppressed pistols, he will be best off using only ammunition that moves with a velocity below the speed of sound (called subsonic ammunition in the trade).  The speed of sound is roughly 1,100 feet per second (fps), and a bullet traveling at this rate of speed in air will generate its own noise.  The sound is called a sonic crack, and it is normally almost as loud as an unsuppressed gunshot.  The most commonly used centerfire pistol cartridge in the United States, if not the world, is the 9mm, although it is slowly being phased out in U.S. law enforcement by the more effective .40 S&W.  Common loadings in 9mm Luger have been 115-grain bullets propelled at roughly 1200 fps.  Statistics have indicated that the 115-grain bullets overpenetrate, and are not as effective as heavier 147-grain hollowpoint bullets moving at the more sedate, surprisingly more effective subsonic velocity of roughly 1000-fps.   A number of experts have stated that an impact velocity between 700 and 900 fps is physiologically far more effective than moderately higher, supersonic velocities with pistol caliber bullets.  That is the reason why the 115-grain 9mm round at 1200 fps has never worked as well as a slower, heavier bullet.  It goes right through, wasting much of its limited energy beyond the primary target.  This fact has been apparent since World War I, but keeps getting forgotten in the search for more power with pistol cartridges.    One will have to get well beyond 2200 fps to achieve the second order of magnitude, and that can only be found with rifle cartridges.

 A 9mm suppressed pistol can be very quiet when combined with a silencer of moderate size.  I conducted a small silencer demonstration for a meeting of chiefs of police on the lawn of a city hall in a large city in the Southeastern United States, during the spring of 2001.  I fired three hand-cycled 9mm shots through a Glock 17 connected to a 1.25 x 7” wet can, directly down and into short grass.  The shots were fired about six feet away from a small assembly of the chiefs while they were standing on a sidewalk during a break.  The bullets were 147-grain subsonic hollowpoint, traveling at 1020 fps.  The shots were so quiet that caterers carrying food in for the meeting’s luncheon on another sidewalk 40 feet away did not even turn their heads as they walked.  While my back was to those food workers during the demo, the chiefs lost no time in pointing this out to me afterward.  The chiefs were not comfortable with silencers of this nature being in the hands of civilians.

Sound levels are not always what they appear to be.  I remember watching an annual contest for the world’s loudest human on TV.  The finalists consisted of a drill sergeant, an older female town crier from England, and a 13-year-old girl.  The sergeant and the older woman had deep voices that may have sounded loud to humans, but the sound meter was not impressed.  The young girl was the last to compete, and gave out a short, high-pitched squeal that wasn’t very impressive, but peaked the meter.  She won the contest handily, causing the others to slink off in humiliation.  A high-pitched sound can be louder than a low-pitched sound without appearing to be so to the human ear. 

A good, expensive, calibrated sound meter is the only device we currently have that can give us authoritative, repeatable numbers.  If a suppressor sounds good to a meter it will probably sound good to a human ear as well, but variations in pitch and duration do make some cans of equality by a meter’s standard sound different to the human ear.  While human ears can’t give us repeatable standards, they should still be considered as the final judge of a silencer’s effectiveness.  As we move into the 21st Century, silencers are getting smaller and more effective for their size.  In most situations a fair amount of suppression is all that is required, and one can shouldn’t be rejected because it is a dB or two louder than another.  Silencers, like firearms, are working tools and they should be as light, robust, dependable and effective as possible.  In the future we will see silencers more integrated into the lives of firearm users in the civilian, police and military sectors.  They protect hearing, allow command and control, and permit stealth in those areas that call for it. 

Sound levels are measured in decibels, commonly abbreviated as dB.  The scale is confusing, because it is not linear.  It starts with 1 dB, which is the lowest sound a human can hear.  Each increase of 10 on the dB scale is roughly 100 times greater.  Because the scale expands exponentially, as it nears the top the numbers mean far more at that end than they do near the bottom.  Soft speech is rated at 65 dB, or .00004 pounds per square inch.  A .38 Special revolver is rated at 161 dB, which is equivalent to .35 psi of pressure.  If you hear an impulse sound of this level three feet away your unprotected ears will hurt and ring for days. A .308 rifle with a short barrel and a muzzle brake will deliver 172 dB, which is equivalent to 1.2 psi.  If someone fires a rifle of this caliber in a small room those inside will bleed from the nose and ears from the shock.  A level of 231 dB is equivalent to 1,000 psi, and exposure to a sound level of this magnitude will cause immediate death.   A .22 LR pistol reaches 155 db, but a good suppressor can quench that down to 114 dB.  This is a reduction of roughly 40 dB, and the resulting impulse sound will not normally be noticed 30 yards away.  A silencer is considered to be good if it will reduce sound 30 dB in the dry mode, a reduction of roughly 1,000 fold on a linear scale.  Many on the market will only reduce sound by 20 dB. A 9mm pistol will reach 160 dB, and can be suppressed to 135 dB dry, and about 126 dB with a good wet can.  A .40 S&W pistol will reach about the same dB level without a suppressor, but can be reduced to about 130 dB with a similar can.  The .45 ACP is a little louder than either of the two, unsuppressed, but can only be reduced down to about 134 dB with a wet can.  Its silenced report can still be heard up to 60 yards away, but casual bystanders may not recognize the sound as a gunshot.          

A good bullet for the .40 S&W cartridge is the 180-grain Federal Hydra-Shok JHP, which moves at about 1000 fps out of a 4-inch barrel.  In general terms, this .40 caliber load will be about 20 percent louder when fired though a suppressor of a size similar to the one mentioned above, with a 9mm, 147-grain JHP load fired at a similar velocity.  Bullets available for the .45 Auto or .45 ACP (Automatic Colt Pistol, developed in 1905) range from 185 to 260 grains in weight.  Velocities run as high as 1000 fps with the lightest bullets, dropping down to as low as 800 fps with the heaviest.  While one might think that the .45 Auto should make no more noise than the .40 S&W, this is definitely not the case.  Even after being suppressed with a very effective silencer, the .45 Auto can be expected to be about 20 percent louder than a good suppressed .40, and almost 40 percent louder than a suppressed 9mm subsonic round.  We are speaking in very general terms, and individual cases will certainly vary from this rule of thumb. 

The 9mm is a very quiet round when properly suppressed, yet it still packs a powerful subsonic punch. The industry has learned a lot about building hollowpoint bullets over the last 15 years, and now has some (like the Gold Dot) that perform very effectively.  Black Hills now makes a truly subsonic 147-grain FMJ 9mm round that can be used in subguns and pistols in situations where suppressors will not handle HP bullets.  Because the 9mm is the quietest of serious calibers when suppressed, and because it is very common, much of the security, police and protection industry in the world has settled on  9mm for suppressed pistol fire.  The 9mm is very available, relatively easy to control, and provides very quiet subsonic fire.  It is the standard of the industry, and many have found that it doesn’t pay to buck standards.                




            Although it may not be immediately obvious to some, existing barrels on Glock pistols are unsuitable for the attachment of suppressors because they do not project far enough from the front of the slide to allow attachment.  While aftermarket barrels are available with threads, they are almost always RH threads.  In addition, many of the aftermarket barrels have chambers that are too tight, and these will prevent the weapons from cycling.  While factory barrels will usually fit and function well, the aftermarket barrels will often require hand fitting in order to work in a Glock pistol.  While the aftermarket manufacturer may not think that this is a big deal, the owner of the pistol will disagree.  While fitting is not normally hard, one needs both the tools and very specific knowledge in order to do it correctly, and this may turn out to be a highly frustrating and ultimately insurmountable obstacle.  Three of many suppliers of aftermarket, threaded barrels are Brownells, Federal Arms Corp. and Fire Dragon.  None of the aftermarket barrels will ever work as smoothly out-of-the-box as a factory Glock barrel.  Glock barrels have sloppy chambers that usually allow them to work with any ammunition made for the parent weapon.  They are built with proper tolerances in all the right places, and are covered with a very hard coating that will not gall.

            The owner of a pistol that he wants to get suppressed is often shocked to discover that he will have to pay from $150 to $600 for a barrel that will allow him to mount a suppressor to his weapon.  A threaded .380 Makarov barrel, by contrast, often goes for as little as $50.  A suppressor may cost as little as $400, or as much as $1,200.  The transfer tax for a silencer to an individual is a one-time fee of $200, while a federal transfer to an institution or law enforcement agency goes free of charge.  A few Glock pistols have barrels long enough to thread if they are installed on shorter models.  If you have a local Glock dealer who is friendly to your cause you might be able to purchase a suitable barrel from him.  Bring your pistol and make absolutely sure that it will fit and function before purchasing.  Another hurdle is threading a barrel that has a hardened coating.  This can be done by a competent gunsmith with a lathe and a carbide, single-point threading tool.  The barrels are a little on the thin side, but they do have more metal in their walls than some other pistol barrels.  The Makarov barrel, for instance, is 3.7-inches long, and only weighs 1.7 ounces.  Thin as they are, I have never heard of one bursting.   Manufacturers of silencers have a vested interest in threading barrels accurately, so they will fit their silencers to line up axially and function properly.  It is essential that the rear end of the silencer clear the tip of the operating spring’s guide rod and frame during the cycling process.  This can usually be accomplished if the shoulder on the barrel projects 3/8 of an inch in front of the slide.   If there isn’t enough clearance the weapon won’t cycle at all, and damage may be done to the barrel,  the guide rod and the rear of the can.


Wipes, Ablatives & Coolants


            There are several methods of enhancing performance of standard models of compact silencers.  Some of the older models of silencers used a system with wipes.  Cans with wipes are rarely used anymore, but they are fairly efficient when new.  Wipes consist of discs of elastic material that bullets can penetrate.  The bullet penetrates one or more discs, and then those discs close up to some extent to contain propellant gas within the can.  Hollowpoint bullets cannot be used with wipes.  Accuracy usually runs from poor to horrible, and velocity is diminished.  The number of shots that can be fired through such a system run from 3 to 12, before the wipes must be replaced.  Sometimes such cans are used in combination with an ablative or coolant, such as grease or water-filled gel.  Cans with wipes are generally special purpose, very small, and are rarely used in this day and age.  They can be useful in a pilot’s bail out kit, where a sidearm will only be fired in an emergency, and not often.

            Some cans are built with baffles that are designed to be used in a dry condition.  These cans are often larger and fairly effective – say 1-3/8-inch in diameter, by from 5 to 11-inches in length.  Most of these cans improve in efficiency with the use of a small amount of grease in the rear chamber.  Since the products of gunpowder combustion are water combined with unburned powder particles and various corrosive acids, the use of a little RIG (rust inhibiting grease) will serve to protect all of the internal metallic components from corrosion, to some extent.  It is primarily a matter of which gets into the metal’s pores first – corrosive compounds or grease, as to the degree of internal corrosion a can will suffer.  Most suppressor manufacturers now ship their cans with the primary chamber coated with RIG, a practice that will prevent a lot of corrosion.  The primary expansion chamber should be recoated after each soaking or cleaning in order to maintain protection.  Expanding gasses from each shot will carry the protective material deep into every crevice.  New greases are coming out all the time.  Dry cans are typically larger in diameter than wet cans, and the diameter can get in the way of sights, forcing one to use the imaging technique of aiming.

            Wet cans usually vary from 1 to 1-1/4-inch in diameter.  A 1-inch diameter can will allow the use of sights unimpeded, while larger diameters will normally occlude or impede vision through the sights.  An ablative is a material or compound that erodes or sacrifices some of itself in order to protect and cool the underlying strata.  A coolant will mix with the hot gasses coming from a pistol barrel, quenching the flame front to some degree, and cooling the gasses.  Since the powder charge in a 9mm subsonic load is only about 5-grains, that will result in about 3.5 grains of gas combined with 1.5 grains of unburnt powder.  It should be pointed out that most of the powder burning that takes place will do so before the bullet ever moves out of the cartridge case.  A pistol is fairly similar to a pneumatic airgun, except that it uses the more powerful effect of burning, hot, expanding gas, rather than compressed air.  When this hot mix of gas and particles hits a small amount of water, grease or gel in the primary expansion chamber in the rear end of a wet suppressor, it will mix with and be rapidly cooled by that material.  The net result is that a small-diameter wet can will provide silencing performance that is all out of proportion to its size.  A wet suppressor may be incredibly efficient at silencing the noise of a gunshot.

            The most common materials used in wet cans are greases, foaming greases, soaps mixed with water (shaving creams and gels), and plain water.  Grease will last for as many as 40 shots, and has the advantage of protection against corrosion.  Water will last between 6 and 12 shots, depending on the interior volume of the can and the complexity of the baffles inside.  If grease is used it should not be overdone, as it can get in the way of the bullet path, and this could cause problems with baffle strikes and accuracy.  Some cans have tolerances large enough to allow the use of HP ammunition.  Others require that only FMJ ammo be used.  Since semiautomatic weapons always open before the pressure has dropped completely inside suppressors, the expanding gasses will usually come back out the rear end of the barrel.  Filthy goo shoots out both ends of the weapon, and this can make the wet can unpleasant to operate in many situations.  Some may not mind the mess, but others will.  A military man on a mission will want grease or water in his can to improve the stealth of the operation.  A lawyer in a three-piece suit and out to impress his buddies behind the courthouse will be less than pleased with black grease spots on his $400 silk tie.




            Again, a small can of an inch or less in diameter will not get in the way of most pistol sights.  Cans larger than an inch in diameter will occlude the sights.  Some put another set of sights directly on the exterior of the can.  Others install extended sights that are higher than the existing factory sights.  Since these are specialty items they will be far more expensive than factory sights.  Still others simply sight down the suppressor tube.  Most modern sights have a white dot and square, or three white dots that will stand out fairly well.  These sights can be used to line up towards the area where bullet impact is intended, regardless of whether the silencer covers that or not.  With practice, any of these systems can be used effectively, especially in subdued light.


Hand Cycling


            Most locked-breech, recoil-operated pistols are very difficult to get to cycle.  Remember that they were never designed to be suppressed.  While most pistols will last through many thousands of rounds of normal fire,  suppressed fire can be expected to shorten their useful life.  Common techniques used to enhance cycling involve altering cam angles, lightening the operating spring, lightening the suppressor with light weight materials or flimsy construction techniques, and the use of recoil boosters.   Altering the cam angles and the use of a lighter weight operating spring (most standard operating springs run from 18 to 25 pounds) may cause damage to the host weapon and could result in severe personal injury to the operator or bystanders.  The use of a recoil booster will enhance cycling, and if a limited number of rounds are expended the weapon may not be harmed by this.  If a lot of rounds are expended the pistol will eventually suffer premature wear and damage.

            While military operators and police want a weapon that will cycle by itself each time the trigger is pulled, there are others who may not mind hand cycling.  Hand cycling is identical to carrying out a malfunction drill.  When practiced, it can be very fast and almost instinctive.  Hand cycling will result in the cleanest operation, because the breech will remain closed, causing all the filth generated to go out the muzzle of the suppressor.  Hand operation will also be the most silent, as silencers are designed to stifle the flow of gas and noise from the muzzle, not back through the opened breech of a semiautomatic weapon.  The worst situation will result with a weapon that only cycles some of the time.  One will never know when to hand cycle, and when not to, and that confusion will result in indecision and lost time.  If the piece actually cycled properly, racking the slide will eject a perfectly good round out onto the ground. A weapon that is hand cycled will not be subject to the slamming that results from the movement of a barrel that weighs three to six times what it was designed to because of the added weight of its silencer.           




            The standard manufacturers (Remington, Winchester, Federal, etc.) supply subsonic ammunition in 9mm, .40 S&W and .45 ACP.  Black Hills offers an uncataloged 9mm FMJ bullet loading that runs about 950 fps in a handgun and remains subsonic out of a subgun.  The general rule of thumb is to use FMJ is all but tactical situations.  It feeds better and will usually stay in one piece if it strikes a baffle.  Load your own if you have the time and