Suppressors - How Much Do We Really Know About Them?

Suppressors - How Much Do We Really Know About Them?

The ASE range of suppressors is favoured by rifle maker Fabian Connolly for their durability and compactness

Most people own one or more of them and those who have paid serious money for their devices generally assume they have the ultimate in suppression and that they know everything that needs to be known about suppression.  This is nonsense.  I have discovered through hundreds of interviews and hundreds of hours spent in experimentation that very few people indeed know anything about suppression.  The reason is simple enough.  The people who write about suppression and more especially the “rocket scientists” who show off their toys on you tube know very little about the science of sound and the people who have done serious research are keeping the trade secrets to themselves.  How many times have I listened to some self-styled expert sound off about the merits of one suppressor over another who doesn’t understand the basics of sound transmission?  If I were to be brutally honest I would have to admit that despite reading everything I can find about this particular branch of ballistics and years of experimentation with various bullets, loads and suppressor designs I have come to the conclusion that even well-informed people are guessing.  I have consulted otherwise knowledgeable engineers who simply do not know exactly why one design is effective and another isn’t.  As I said there are people who really do know the science of sound and sound suppression but they have gained this knowledge through research and experimentation and are backed by large budgets provided by, in some cases, the military and in others by military industries and every development has come at considerable expense – far more than the ordinary backyard experimenter can afford.  Furthermore they can call on fully equipped workshops equipped with the latest in machining equipment to turn their ideas into prototypes which are then tested using even more sophisticated equipment.  When a manufacturer puts a new design for a 30 calibre rifle suppressor on the market at £1,000 a pop he has already laid out considerable funds on research, development and tooling and expects to recover his investment and show profits and is unlikely to discuss his research in some shooting magazine.  The gun journalist who does a few test fires and promotes the new product is writing for the consumer not the developer.  People like myself who have an interest in this topic all agree on one point – there is a LOT we don’t know and even more we are not being told.  I know several people who have built and sold suppressors commercially and even these, while they may understand their particular product intimately, have more questions than answers about the wider field of ballistic sound suppression.

This remarkable snapshot was taken using a suppressor with a transparent tube.  It shows the bullet departing the muzzle followed by a blast of hot, glowing gas that has become trapped in the expansion chambers and is making its way towards the baffles.  The bullet will have reached the target while the gases are still swirling around inside the suppressor before emerging cooled and slowed.  The suppressor is doing exactly what it should

Suppressors are referred to colloquially as “Cans” and “Silencers”.  The terms “Moderator” and “Suppressor” are more precise and mean the same thing – a device fitted to a firearm to reduce its sound signature.  The decibel scale used to measure sound is logarithmic.  Gun shots are not composed of a single frequency but produce a wide band of frequencies in a characteristic mix that the human brain soon learns to associate with the discharge of a firearm.  A suppressor can deceive the brain and the suppressor that is especially good at eliminating higher frequencies will seem quieter than one that eliminated lower frequencies.  The threshold of human hearing is zero decibels.  A quiet conversation is 56 decibels.  A BB gun is 101 db.  A standard velocity 22 rifle is 137 db.  Hearing damage begins at 140 db.  The pain threshold is 141 db.  A heckler & Koch MP5 is 157 db.  A .45 pistol is 162 db.  An M16 is 165db.  A howitzer is 183db and death to an observer occurs at 220db.  The first commercial suppressor was patented in 1909 by Hiram Maxim of machine gun fame and resembled many of the baffle-stack silencers available today for .22 rifles.

 

A Vaime 22 suppressor.  The infamous "Hush Puppy" used to kill guard dogs in Viet Nam.  It used wipes to contain propellant gases.  The Reflex design, arguably the most successful for cost effectiveness, and Hiram Maxim's patent of 1909 which has never gone away and is much copied and was commercially successful in its day

What do we know?  The current state of knowledge among ordinary shooters can easily enough be summarised as follows:

1. Subsonic projectiles are quieter than supersonics which create a supersonic crack.

2. Subsonic (.22) suppressors are more efficient than supersonic suppressors.

3. Some designs are more effective than others

People who have read a little more will know that:

4. Suppressors trap, cool, slow down and then release propellant gases.

5. .22 calibre firearms can be suppressed to the point where they can be called “silent”

6. Automatic and semi automatic firearms are more difficult to suppress

This photo of a black powder hunting rifle taken at dusk gives some idea of what a suppressor has to cope with. 

Tell a knowledgeable shooter that a suppressed .22 calibre subsonic bullet from a locked breech rifle is silent while a suppressed .45 calibre subsonic from a locked breech rifle is not silent and he will probably start talking about something he has seen on line about a De-Lisle .45 ACP silenced carbine.  The truth is that the number of people who have used a  De-Lisle .45 ACP silenced carbine is very, very small and reliable empirical data is just not available.  Everyone knows how the De-Lisle works but nobody has seen one working and nobody has used one.  The last time a WWII De-Lisle was seen in public was in the hands of an SAS squaddie in Northern Ireland thirty years ago and since it has not been seen since one can only assume it is no longer considered state-of-the-art-must-have military hardware.  Respected writers like Ian V. Hogg talk knowledgeably about it but I suspect Ian has never fired one either.

The British WW2 .45 ACP De Lisle silent Carbine was reputedly a successful design and is manufactured today by Valkyrie.  It used standard military supersonic ACP ammunition and a ported barrel to divert gases into a shroud suppressor after which both gases and bullet emerged at subsonic velocities.  The ported barrel is not in favour today and suppressors are generally used with subsonic ammunition

Go on line and look up our transatlantic brethren who seem to get away with stuff that would land the rest of us in some dingy police cell with our firearms seized and a beefy representative of the law of the land asking penetrating technical questions about our activities.  These people seem to have some very interesting suppressed firearms indeed; from suppressed centre fire pistols to suppressed vintage Sten Guns to custom-built locked breech heavily suppressed rifles firing subsonic large calibre bullets.  To be truthful it’s all a bit suspect and one wonders how much of the suppression on display is ballistic and how much is electronic.  In other words real sound waves undergo modification every time they are processed by microphones, speakers, filters, Bluetooth, wifi, mp3 compression and so on.  The guy with the nearly silent 9mm machine gun on YouTube may not be as unobtrusive as he sounds and the Hollywood myth of the 9mm pistol that goes “PHUT” is just that – a myth.  My .22 Anschutz heavy-barrel locked breech varmint rifle with its A-Tec suppressor goes “PHUT” and as far as I can determine ballistic suppression just gets louder after that.  Explaining this self-evident fact is more difficult than you’d think.  I should also mention that the “PHUT” is considerably louder at the enclosed 22 range than it is out on the side of a hill shooting rabbits.

The parts of the T8 reflex suppressor for centrefire rifles.  The design is tried and tested - an expansion chamber that extends backwards around the barrel and baffles.  It is made of stamped, welded steel but corrosion sets in with use and eventually renders it unusable.  Aluminium and stainless steel have more resistance to corrosion

This Swedish Mauser Carl Gustav rifle of 1904 was rebuilt by Fabian Connolly in .45 Colt and fitted with a large .45 suppressor.  It has been used to research suppression and subsonic ammunition

A number of years ago I produced an outline design for my dream gun which I took to a rifle-builder and received a few months later a beautiful customised single shot 1904 Carl Gustav Swedish Mauser in .45 long Colt with a .45 calibre suppressor and mounted with an exquisite 40 year old Pecar variable scope AND a set of Elit Edstrom Swiss target dioptre sights which I licenced and have used as a range rifle ever since.  It’s not everybody’s cup of tea and most people don’t appreciate what it is since it doesn’t fall easily into any of the usual categories.  It’s not as powerful as a rifle calibre nor as accurate as a target rifle nor as long range as a varmint rifle nor as silent as a 22 nor as fast-firing as any of a dozen hunting guns but it opened up for me the arcane world of ballistic suppression.  The range of cast bullet weights available in .451 runs from the little stubby 165 grain round nose through the Keith 250-325 grain Keith semi-wadcutters to the large 400 grain Casull and the velocity range is from 500 feet per second to 1500 fps.  The powders available that can be used go from the fastest Bullseye pistol powder through Slow pistol powders like Clays Universal through Lil’Gun shotgun powder to fast rifle powders like Vectan SP3.  I addition I can, if I wish, legally use Black Powder in it since that is what the .45 Long Colt was originally designed for.  It can be used with any suppressor having an M18 thread and a .46 bore and I have had a lot of fun with it and have learned a lot from it and have blown quite a number of suppression myths out of the water with it.  It doesn’t fill the freezer with venison or rabbit meat or win F-Class competitions but it taught me what I know (and what I don’t know) about reloading and suppression.  I can never sell it because no-one would want it and it is the single firearm in my gun cabinet that I can pick up any time and use to challenge another common ballistic myth or address a tricky suppression conundrum.  After six years It has, as expected, produced some answers and a huge number of questions and the journey of exploration continues.  I sometimes call it my “bullshit suppressor” because of the number of misconceptions it has exposed.

 

(1) The massive A20 fullbore suppressor in aluminium and steel from The Whole Shooting Match  (2)  The little Brocock synthetic suppressor – only two parts and surprisingly effective on air-rifles and .22 rimfires.  (3) The Parker-Hale Rimfire suppressor of thirty years ago – still a good design with 11 baffles.  (4) the most attractive of them all – the simple SAK rimfire suppressor in aluminium with three parts.  (5 and 6 ) the ASE Ultra with double wall construction and 18 baffles.  Complex, a little heavy, hard to clean, not cheap but the most effective of the lot.

When you own a suppressed .45 rifle the first thing you learn is that your 22 is silent and everything else is just suppressed.  There is only one silenced firearm – the 22.  A subsonic 22 bullet is about 40 grains in weight with about 2 grains of powder behind it and the small explosion of gas it produces can be suppressed by just about any container fitted on the end of the barrel  The most silent 22 is a locked breech rifle with a long, heavy barrel rifle with any good quality suppressor.  The least silent 22 is a semi-automatic with a short, light barrel, (lots of muzzle blast)  and a cheap suppressor on the end.  Needless to repeat is the fact that subsonic 22’s are quieter than supersonic 22’s and the supersonic 22 hv, 22 Magnum, Hornet, 223 etc cannot be made silent. It’s not that a .45 bullet cannot be tamed – it can but it is never silent.  The 40 grain 22 subsonic bullet produces about 40 forty foot pounds of kinetic energy.  A 165 grain .45 bullet at 875 feet per second with five grains of pistol powder produces about 100 foot pounds of Kinetic energy - which is not exactly powerful – and a much louder explosion that even a large, efficient suppressor struggles to contain.  Now here’s the interesting bit.  Put the same bullet weight and the same load of 5 grains of pistol powder and the same suppressor on a .308 and the result is much quieter.  We can’t put 4 grains of powder and a 165 grain bullet in a 22 but using what we’ve got we can see that the 22 is the quietest of the three, the 308 is a bit louder and the 45 is the loudest.  A friend of mine calls this “Ward’s First law of Suppression – Big Bore- Big Bang” and I defy anybody to disprove it.  I’ll repeat that: all other things being equal, ie bullet weight, powder weight, velocity and kinetic energy; a large calibre bullet produces a louder bang than a small calibre bullet of the same weight.  I’d like to be able to say I will now proceed to give a theoretical explanation as to why this should be – but I can’t.  I’ve consulted engineers and their explanation is logical.  The larger circumference area of a 45 bullet expressed as  pi(R*R) produces a larger gap for gas to escape through than the smaller circumference area of a 22 bullet expressed as pi(R2*R2).  Big gap Big Bang.  Very good.  Let’s test that.  Put a 45 bore can on a .22 or a .308 rifle and there is no appreciable increase in audible noise which the theory tells us there should be.  You will note I do not refer to decibel meter test results here; the reason is I found them meaningless.  A decibel meter does not measure what the human ear hears and in the case of a 22 a decibel meter rated the closing of the bolt and the ping of the firing pin louder than the suppressed shot – logical for a decibel meter but nonsense for the human ear and brain.  Here the engineer and the experimenter simply disagree and I defy any engineer to prove “Ward’s First law of Suppression – Big Bore- Big Bang” by recourse to the Engineer’s “Big Gap – Big Bang explanation.  At the time of writing this is a ballistic dead end until one of those shadowy military ballistics types breaks the official secrets act to come out of his comfortable retirement to prove me wrong. A Corollary of “Ward’s First law of Suppression – Big Bore- Big Bang” is “Heavier Bullet – Bigger Bang”.  Essentially this means that a subsonic 400 grain .45 bullet produces a bigger bang than a 160 grain .45 bullet.  The reason is that much more powder is required to produce the same velocity in a heavier bullet and this logically produces more pressure and a bigger bang.  This very obvious piece of ballistic fact has been demonstrated many times and is beyond question.

 

Baffled?  Flat baffles seem to work.  Add different baffles, wipes or funnel shaped baffles and there may be an increase in efficiency.  The permutations and combinations of baffles, bullet types, velocities and calibres are mind-bending

Ward’s Second Law of suppression states; “Some suppressor designs are more efficient than others”.  This may seem a bit obvious to Google experts but it needs stating.  Take two suppressors with two different baffle stacks.  A suppressor generally consists of an expansion chamber followed by a baffle stack that first allows gas to expand and cool and then confines it to prevent it escaping the muzzle at supersonic speed.  The first suppressor uses flat baffles and the second funnel-shaped ones.  The first simply blocks propellant gas while the second will “strip” propellant gas from around the projectile and direct it backwards thus slowing the rate and temperature of escape.  It is in the area of baffle design that the serious researchers surge ahead of the pack.  A suppressor fitted with more efficient funnel-shaped “gas stripper” baffles will generally outperform others although the audible difference will be less noticeable in 22 than in 45 calibre.  It is in the area of baffle design that the perfect match of baffle configuration to bullet shape, diameter and velocity shows its advantages.  I would speculate that this type of research is also expensive as it necessitates a lot of trial-and-error and shuttling between a CNC lathe and an experimental firing range equipped with sound monitoring technology.  An idea might produce a baffle design with a particular angle or shape which must then be machined and fitted in a tube mounted on a gun which must be fired with a variety of powders and bullet types and the results compared.  That kind of work is time-consuming.  When the final result has been perfected and marketed the developer will want to keep his research to himself and charge as much as he can get for his product.

 

Suppressed WW2 Sten guns, .30 calibre rifles, wipes, baffle shape - it's all explained in only one serious book that I have found - Alan Poulson's Silencer History and Performance

 

Ward’s Third law of Suppression states: “Fast Powders are quieter than slow powders”.  Here there might be agreement.  Just as the automotive engineer does not want fuel exploding in his exhaust system so the ballistic engineer doesn’t want burning propellant coming out the muzzle of his suppressor.  Fast pistol powders are designed to burn in a short pistol barrel while slower rifle powders may need 22 inches in which to be consumed entirely.  Muzzle blast is unburned powder.  More effective suppression is achieved when powder has been entirely consumed well before the projectile reaches the suppressor.  There are difficulties here.  It has been demonstrated that a bullet that has reached maximum velocity and has begun to slow down within the length of the bore will not perform as well as one that is propelled by an efficient burn and acceleration for the entire length of the bore.  It may even be there is a conflict between efficient suppression and accuracy and that effort must be expended in achieving a balance.  I have demonstrated this by testing fast versus slower powders at 100 yards in my Swedish Mauser .45 Long Colt Carbine and the advantage lies with the slower powder.  Put another way:  shotgun powders are more accurate than pistol powders in a 20 inch .45 barrel.

 

Improvised devices to test whether a suppressed firearm could be further suppressed met with mixed success. Lagging the barrel and suppressor with sound damping material inside a plastic pipe produced a slight increase in suppression efficiency but you wouldn't want to be seen carrying one around a field!

Ward’s Fourth Law of Suppression states: “Not all noise comes from the muzzle of a gun and is therefore more difficult to suppress”.  When 4 grains of pistol powder are ignited in a .45 Long Colt case and a 165 grain .45 bullet launches down the barrel at 500 feet per second, there is audible noise at the breech of the rifle.  This is difficult to prove although all firearms can, under specific circumstances, produce blowback of propellant gases where the chamber pressure has been insufficient to create a seal between a brass case and the chamber wall.  This is dangerous and should be avoided and is one of the reasons why shooters should wear eye protection.  Short of surrounding the breech of a firearm with sound damping material this noise is difficult to suppress.  Further proof of this phenomenon comes from the firing of guns with breeches that blow back to provide self-loading functioning and which have long been recognised as more noisy than guns with breeches that lock closed.

 

Unlike the legions of Google experts the author has actually fired a suppressed sub machine gun - in this case a 9mm CZ Skorpion while the guest of CZ at the Lieberec sports centre in the Czech Republic.  The underground range is equipped with sound absorbing material.  The Skorpion wasn't as silent as my 45 Mauser and the noise in the range was deafening. Presumably the people ice skating above our heads heard nothing?

Ward’s fifth law of suppression is still sort of being tested.  It states “Sound damping materials have minimal effect on the noise of a suppressed shot”.  Many ranges have sound proofing or sound damping materials in the walls which are intended to protect the hearing of those inside and outside the firing point and indeed they do by absorbing sound as opposed to bouncing it around.  From a suppression point of view this is ineffective.  I have often noticed that buildings have minimal further effect on the noise of a shot that has already been suppressed.  I am currently waiting for an explanation of this phenomenon from a sound engineer but in the meantime an electronic engineer has offered the following explanation.  “When you fire a shot inside a building you resonate the materials in the walls and ceiling and the building becomes a speaker”.  It is an interesting piece of information and stresses the importance of what I will call “Primary Suppression”.  In other words insulated range buildings reduce the chances of gun fire annoying local residents but a good suppressor probably does more.

 

Subsonic 165 grain loads from a 30 calibre rifle with a light A-Tec suppressor are quite silent, especially outdoors.  They are ideal for range use but, it should be stated, are probably illegal on deer

Many considerate shooters voluntarily and legally fit their 30 calibre target rifles with factory suppressors to minimise hearing damage when using full-house target loads.  But what about subsonic .30 calibre loads.  This was recently and legally tested by shooting some of the previously mentioned 165 grain subsonic .30 calibre loads with cast bullets at an open-air range.  Several things were immediately obvious;  the noise produced was surprisingly low; accuracy at 100 yards was marginal and disturbance at a distance from the firing point was almost zero.  When the load and velocities were increased, accuracy improved enormously to the point where, at 1650 feet per second accuracy almost equalled a target bullet and noise disturbance when using a suppressor was still quite minimal.  When these loads were fired at 300 yards accuracy was still acceptable.  Obviously a balance can be struck between range, velocity and suppression and full power loads can in some instances be replaced by reduced loads with success.

The most exciting development in recent times is this Wildcat suppressor with a modular multi-calibre design distributed by Ardee Sports.  It features shaped baffles and interchangeable calibre modules

Ward’s sixth law of suppression states what is by now obvious:  “Large calibres can never be suppressed to .22 levels even when subsonic ammunition is used”.  Of course it leaves open the question as to whether further research into suppressor, baffle, firearms and ammunition design can produce improvement.  It is possible, especially with custom-built suppressors to incorporate upgrades and improvements.  An excellent example is the addition of one or more robust and precise funnel-shaped baffles that improve gas retention.  Modern three and four dimension CNC lathes can execute amazingly complex shapes and are being used in the suppression industry.  The modern trend is to take levels of suppression already achieved and execute them in lighter more compact designs.  I sometimes wonder whether suppressors using modern research and design were made larger and heavier would even greater levels of suppression be achieved.  Such research is likely to come from the USA and Finland where there are already  huge suppression industries.  Legislation makes it difficult to design and produce suppressors in the UK or Ireland.  I believe we will see such improvements; indeed I hope we do as I have 18% hearing loss from a lifetime of unsuppressed shooting and would wish the like on no-one.

Ward’s seventh law of Suppression states:  “Suppression and accuracy are in conflict and genius is required to balance both”

Back in the Viet-Nam era, we are told, the brave fighters of the Viet Cong whom the Americans have traditionally portrayed as uncouth savages as they do with anyone who opposes them, used guard dogs as a simple, cheap and ingenious early warning system against infiltration by US special forces.  The Americans, who wanted to neutralise these canine guards developed the “Hush Puppy” pistol which was a 9mm, usually Walther or Beretta Pistol with a suppressor attached.  Hence the name “Hush Puppy”.  Being American the Military came up with a complex solution that achieved a reduction from 160 decibels to 132 decibels and employed fibre “wipes” to retain propellant gases.  The wipes, as the name suggests, actually touched the bullets and while they stripped gases efficiently they had a working life of only 35 shots before replacement became necessary.  They had a detrimental effect on accuracy that limited their use to extreme close range.  Reports from the time suggest the dominant sound from these suppressors was the sound of the bullet striking the wipes and the target and that the actual gunshot was effectively silent.  If this is true then Ward’s seventh law of Suppression is wrong.  Is it true?  I think not.  Evidence from people demonstrating modern pistol suppressors online suggests effective suppression may not have been that great.  One can further imagine the difficulty the maintenance of wipes created for soldiers in combat.  In more recent times the Israelis took the obvious step of developing and using suppressed firearms using .22 calibre bullets which are less troublesome.  The energy differential between a .22 versus a 9mm subsonic bullet is approximately 70 versus 140 foot pounds.  If the shooter is trained to use the “double tap” technique and keeping in mind the greater .22 reliability then the “Hush Puppy” may have been over-engineered to say the least.  The final demise of the wipe came in the eighties when US Federal law classified them as restricted parts of a suppressor requiring extra paperwork for their procurement and replacement.  People found other means of suppressing their pistols.  

 

How much suppression do you require? Out here in the wilds of Donegal there's nobody to hear

Ward’s eighth law states:  “The effectiveness of a suppressor depends on its intended use”.  Many years ago an English Hippy with advanced opinions on how the paddies should behave moved into a squat beside my favourite hunting spot in east Clare and proceeded to go for the guards every time he heard me fire a shot.  In those pre-commercial poaching days there were lots of deer and a shot usually meant meat and the guards soon learned to ignore this nuisance.  I had nothing to gain by advertising my activities to this principled parasite so I had Fabian Connolly suppress my rifle.  Fabian, who knows a thing or two about rifles, hippies and suppression recommended a lightweight model as a compromise between noise reduction and portability.  Shortly thereafter I shot a deer behind the hippy squat and watched the fun.  The long-haired friend of the Earth fired up his minibus and drove at speed into the wood across the road from his squat – obviously intending to confront the enemy of the Earth (me).  I recalled something I’d read about suppressors written by a Finn: “The suppressor doesn’t conceal the shot but the location of the shooter”.  Connolly had sold me a 100% effective suppressor.  By the same token I often used my suppressed .22 rifle in the fields behind my house.  This gun is almost completely silent and yet after a time my friendly neighbour was able to say to me:  “I heard the little slap off your rifle this morning – did you get a rabbit?”  He had learned to identify the much reduced report of a suppressed 22 Anschutz.  The human ear isn’t just sensitive – it LEARNS.  For a few years I carried two types of ammunition when deer hunting; a full powered soft point thirty calibre load designed to kill humanely out to 250 yards and a second subsonic load for situations where I wanted to keep my activities as quiet as possible as when there were walkers in the vicinity.  I never used the subsonic loads and found the suppressed full-power loads perfectly suited.  Rabbit hunting was quite different and farmers often asked me to shoot rabbits in fields near houses.  For this situation .22 subsonics were perfect. 

The ASE range of fullbore suppressors are forged from anodised stainless steel and near indestructible

As with all things in life there is a lot of silly talk and bragging about suppressors and which centrefire rifle model to buy and fit on the greatest rifle ever made (no one admits to owning a useless or, as in my case, an experimental rifle).  But then choosing a can is a business requiring some thought.  How do you choose?  Firstly there is the muzzle thread.  You don’t just thread the gun and bung a can on it.  Threads vary as do the size and weight of suppressors.  A slender barrel requires a smaller diameter thread such as perhaps half inch UNF or BSF.  A heavy barrel might require an M18 thread.  Very few people know much about this kind of thing or they know a little and claim to be gurus.  It is best to consult an engineer/toolmaker/riflesmith.  What you do NOT do is give the gun to handy joe and let him butcher it with an out-of-true thread.  I’ve seen enough of these to convince me very few people indeed can be trusted to take the time to set up a lathe to do a suppressor thread accurately and safely.  If the suppressor is not true to the axis of the bore it is a botch.  Then there is the can itself.  It should suit the gun and be specified by the manufacturer for the calibre in question and suited to use ie hunting or range work.  A hunting can will be lighter and a range suppressor more robust.  There is no rule but common sense dictates that light and tinny will burn out faster than strong and heavy.  A  sealed suppressor is difficult to maintain while a strippable design can be cleaned and rustproofed.  A beautifully machined strippable modular aluminium model will cost a lot more than a stamped, welded but robust type.  I confess to a degree of confusion myself when it comes to choosing from the many designs on the market.  I own two cans in particular that I think are right for the job and value for money; an A-Tech model in 6mm made from heavy forged steel suitable for serious varminting and another in 7.62mm and light aluminium for deer hunting.  In both cases Fabian Connolly helped me choose and then fitted the suppressor.  I have owned a couple of English models that were less satisfactory.  One was a sealed steel model that rusted to the point of becoming dangerous and another well made modular design just bound up and can no longer be stripped.  The problem with the second is of my own making because I left it too long without stripping and oiling but it highlights a problem.  I have a friend, an engineer/toolmaker who courageously flushed a suppressor with ammonia followed by light oil and managed to clean it pretty thoroughly.  Whether he has created a corrosion problem remains to be seen.  Another acquaintance fills his suppressor with bore solvent and lead shot and gives it a good shaking to remove residues.  Again this method scares me – what if a stray lead ball got in the way of a bullet?  Perhaps a buyer needs to look into his soul and ask himself: “Am I prepared to clean the damn thing every time I use it?”  Does “Yes” mean modular aluminium and “No” mean sealed steel?  I rest my case because I simply don’t know.  My .45 can has long had a welded muzzle plug as a result of a single black powder round fired out of idle curiosity and ever since I have eyed with dismay and trepidation the rapidly accumulating layers of soot, carbonised unburned powder and homemade beeswax-lanolin grease that are adhering to the baffles.  Connolly tells me to stop worrying and keep shooting but I can only manage the latter.  Ammonia is becoming hard to find.  So how much does one spend?  I feel I have to offer something to the bamboozled shooter.  Generally when you pay more you are paying for lightness and compactness so if that’s what you want then lay out £1,000.  If you just want suppression then pay less for a bigger, heavier model that you can strip and clean.  If you are an occasional shooter then go cheap and look after it.  If you own a 22 then just get something that you can clean easily – they all work.  My .22 Anschutz sports a very complex Norwegian double walled job made of heavy forged steel and is a horror to clean – there are 3-piece aluminium jobs for less money that work as well and can be wiped out with an oily rag.  The most robust suppressor I have used is an ASE Utra which is forged steel, heavy, sealed and indestructible.

 

The oil filter suppressor. Best not to try it unless you want to damage your gun, your person and your reputation.  Besides it is almost certainly illegal. This is a contrived photographic montage not an actual test

Is there a final word on suppressors and suppression?  The population of this island is increasing and more city people are moving out into the country to escape overcrowding, crime, drugs, noise etc etc.  Invariably some of these people lack understanding of things like spreading slurry on pasture, fox control, shooting ranges, hunting, dogs worrying sheep and country pursuits in general and will complain stridently when they see evidence of behaviour that is beyond their experience.  The suppressor is the single most effective means of pacifying these people by keeping them in ignorance of what they don’t understand.  It also protects our hearing and it is a wonderful invention.  Its possession also requires a licence and this should be kept in mind.  It is classified as a firearm and cannot be bought, sold, transported or manufactured without paperwork.  It should be removed from a vehicle when not in use as its loss is near enough the loss of a firearm with all the trouble that entails.  As a firearm it should be stored like a gun in a gun cabinet.  Making your own can is illegal in the same way as making a crude gun is illegal and doing so is a gift to some policeman’s promotional prospects.  I know a chap who decided to design and make an affordable centrefire suppressor.  He manufactured a prototype and foolishly sent it to the relevant authorities with a cover note saying he wanted to manufacture and market his “invention”.  He is out of business and has entered the crime statistics.  I do not know whether modifying or improving a suppressor at home is illegal.  Common sense dictates that great caution is called for.  Light hunting models are unsuitable for range use where they are likely to overheat and deteriorate from intensive use.  Range models should be robust.  They can be dangerous as when they are fitted loosely or cleaned carelessly resulting in the bullet striking the suppressor’s internal parts.  They need maintenance.  Steel suppressors can rust and aluminium models can bind up and should be partly disassembled after each use and reassembled before each use.  Putting a smaller suppressor on a larger calibre gun can be especially dangerous.  When stored they should not be left on the gun as corrosive substances can leak down the bore.  Barrel cleaning patches should never be allowed to get into the suppressor where they become an obstruction.  Reloaders should be cautious when using gas checks lest they detach in the suppressor.  Cleaning and maintenance should be as per the manufacturers’ instructions and common sense is required when using powerful solvents.  It should be kept in mind that a suppressor designed for a low powered firearm may not withstand the pressures in a high-powered firearm.

 

This is a photo of a rifle being threaded on a lathe by a skilled operator.  There is no other way to do it without risking damage to a valuable firearm. Amateur handymen should be avoided

I would like to see more research reports on the use of coolants in suppressors. My own experience with wet suppressors suggests the reduction is not great

This table of research results from 1966 suggests significant sound reduction has been achieved by the use of suppressors but not to a level we would regard as silent

These days the fashion is for “Ten things you need to know about….”  I have put together the following ten questions to point the way towards a more informed understanding of suppression and to highlight what we DON’T know.

10 QUESTIONS ABOUT SUPPRESSION

01 All other things being equal; why is a suppressed subsonic .22 bullet almost completely silent and a subsonic .45 bullet not?

02 Why is a 160 grain suppressed subsonic .45 bullet quieter than a 320 grain  suppressed subsonic .45 bullet?

03 All other things being equal; why is a suppressed subsonic .30, 9mm or .30 bullet quieter than a suppressed subsonic .45 bullet?

04 Is a .45, .30 or 9mm subsonic bullet impossible to suppress completely to .22 suppressed subsonic levels?

05 All the experts are talking about the importance of baffle design - why do baffles make so little difference over a straight expansion chamber?

06 All the experts say a tight fit in the suppressor bore is important but why is a .45 suppressor on a .22, .243 or 6.5 supersonic rifle so effective?

07 All the experts say a baffle MUST be shaped like an inverted funnel - why does this make so little difference when tried?

08 Where is the noise of a shot coming from - the muzzle or the breech or through the barrel wall?

09 Why does a suppressed or unsuppressed shot fired inside a container full of sound damping material sound so loud to an observer standing outside the container?

10 Why is fast burning powder more suppressible than slow burning powder?

 

If you can answer all 10 questions then you are either (a) a ballistic genius or (b) you haven't a clue how suppression works.  I fear I fall into both categories!!

An interesting old illustration of the De Lisle Silent Carbine showing a cutaway with exposed baffles