Suppressors

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Concussive force 2

GETTING AN EARFUL

(Using suppressors)
Realise that there is an absolute relationship between gunfire and hearing loss.

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Alex Gale

‘Latest studies show that one in ten New Zealanders suffer from hearing loss’.                                                           (Bay Audiology Client Newsletter, Summer 2009)

I remember it like yesterday, even though it happened over 30 years ago. A friend and I were commercially hunting Lake Poteriteri, a magnificent lake in South-West Fiordland. This day we elected to hunt up towards Lake Mouat, a small lake on the western side towards Long Sound. Most times while meat hunting we hunted individually, but this day we were together, probably because we intended heading up the face beside the large waterfall and into the valley leading up to the lake. It was a bit wet, not an unusual experience for Fiordland, which meant the crown fern was dripping wet and we had to clean our scopes occasionally.

As usual we were on the lookout for deer, and as we sneaked over a small rise a stag emerged from our left, only to stop broadside on about 20 metres away. Before I could say, “Hi mate, want a trip to the freezer?” I heard a blast beside my right ear and saw a spray of water erupt from the wet chest of the deer as the bullet impacted him. I wasn’t as ready to celebrate a great shot and the spectacular spray of water as Ronald was, as my ears were ringing very loudly and, in fact, that ringing stayed there for some time. I wasn’t a happy hunter. We can look back now and realise the damage that must have caused, but of course we know more about these things now.

My hearing did recover a bit after a while, and it wasn’t until I hit my 50’s that I realised I had a real problem. I knew my ears weren’t quite what they should be, but it took my son, Tim, to well and truly rub it in one roar while we were out hunting Sika stags. He’d shot quite a nice 8-pointer earlier in the day after calling the stag in and so it was my turn for a shot. Naturally I was hoping to do one better than him and so when we came to a really promising area I was looking intently. I must have been looking too hard because I snapped a twig underfoot and then Tim whispered, “Did you hear that? I think it was a stag.” I had to confess that I hadn’t heard a thing, but he was certain, and then he spotted it. With the binos I could see antlers flicking occasionally across a gap in the scrub as the stag moved its head every so often, even though it was only about 35 metres distance. After a period of time, about 25 minutes, with Tim giving the odd roar and a few meows, the stag simply walked a few metres and stood in the open looking at us. He wasn’t worth shooting so we left him for another year, but I realised afresh, if ever I needed reminding, just how important our ears are for successful hunting.

When I started hunting in the 60’s I did a lot of range shooting as I experimented with reloads, and of course when commercial hunting I fired a good number of rounds at deer and pigs. As well, I’ve had over-enthusiastic mates, as mentioned, fire shots quite close to my ears. The combined consequences now mean my hearing is not fantastic and I now normally wear hearing aids. It didn’t deteriorate immediately and, in fact, my hearing was superb in my commercial hunting days, but it did catch up with me later. Hearing loss is not to be recommended. Modern technology is amazing, but NOTHING can replace your original good hearing!

Keys to becoming a skilled hunter are good vision and hearing and it goes without saying that being be able to hear the sounds of deer and of other hunters is incredibly important. We’re always wise in hindsight and if I’d known what I know now, I’d have taken steps in the past to protect my hearing. Incredibly, after WW2, doctors taught that hearing loss was only temporary, and even in the 60’s you couldn’t buy ear muffs. Now I dare say that the noise of even a .22/250 cartridge is a lot less than an anti-tank gun or a volley of .303 shots, but the effect is much the same – damaged ears. When I reluctantly first went to an audiologist he told me there were lots of hunters my age with the same problem. Cold comfort indeed.

So what’s the deal with gunshots? How much damage do they cause and what can we do to prevent hearing loss? Sound pressure is a direct physical measure of sound intensity and is measured in decibels (dB) of sound pressure level (SPL). An increase of 6 dB SPL is actually a doubling of sound intensity. Therefore, a rifle shot of 146 dB SPL is actually twice as loud as 140 dB SPL. We know that continued exposure to noises above a level of 85 dB eventually affects a person’s hearing.

Noise levels above 140 dB can cause hearing loss after just one exposure. Most firearms range from 140 to 170 dB, loud enough to damage your hearing instantly. Because a single gunshot is so intense, it’s always above safe noise levels. Guns with short barrels or ported barrels, the latter designed to lessen recoil, increase the noise associated with each shot. Complaints of diminished hearing and a sensation of muffled hearing or ringing in the ears after noise exposure are indicators of damage due to excessive noise. The actual decibel level varies, based on the calibre, barrel length and muzzle devices such as muzzle brakes, but to give you some idea, the likes of a .308 or .30/06 cartridge will be around 165-170dB. A muzzle break on a magnum rifle can add 5 or more decibels.

Realise there are only two kinds of shooters in the world – those who use effective hearing protection and those who have or will eventually suffer hearing loss. A study by researchers at two American universities revealed that half the hunters surveyed suffered from tinnitus – a constant ringing in the ears. Tinnitus is often a sign of noise-induced hearing loss. Thirty-four percent of hunters reported having difficulty with conversational speech as well as hearing in other social settings. Realise that there is an absolute relationship between gunfire and hearing loss. A lifetime of shooting almost always leads to some hearing loss, although genetic predisposition may make it more severe in some individuals and less severe in others. The damage from exposure to gunfire is cumulative over time, and chances are high that shooters will eventually have difficulty understanding normal speech.

So how can you protect yourself?  You can protect your ears and what enters them or you can limit the noise from your rifle by using a suppressor.

Ear protection: all the following are recommended for use on the range.

  1. Ear plugs: simple to use and cheap, but give nowhere near the level of protection as more sophisticated devices.

 

  1. Ear muffs: top brands are good, but beware of cheap options. You probably get what you pay for. Can be a bit clumsy to use. Can be used with ear plugs to give the ultimate protection, but if they come into contact with the comb of the rifle this can increase the sound level pressure to your ear, thus negating the effectiveness of the muffs. Muffs should be replaced when the internal foam loses its sealing ability.

 

  1. Electronic hearing protectors available in ‘ear muff’ styles or traditional ‘hearing aid’ style. Some of these devices limit noise exposure, using sound compression technology that limits the peak intensity of loud noises presented to the ears, while also having the ability to amplify other desirable sounds in the hunting environment.

 

  1. Suppressors (or sound moderators)
    For out in the field nothing beats a suppressor, which deals with the source of the problem: the blast. Their use is compulsory for professional hunters now and for good reason – while they add weight to your rifle, they save your hearing, plus significantly reduce the recoil. A suppressor will give a noise reduction of about 30-40 dB’s depending on the suppressor you buy and the cartridge you use. The MAE suppressor on my .30/06 makes it sound like a .22 magnum, and one day at the Taupo range a guy asked me if I was using subsonic loads! In fact I was shooting 165 gr bullets at about 2900 fps. He was impressed, to say the least. The other advantage with a suppressor is that your shots won’t disturb game to the same extent and sometimes animals have no idea where a shot is fired from. Another advantage of using a suppressor and good hearing protection on the range is that your concentration levels will increase and flinching will decrease, due to less noise and less recoil, enabling you to shoot more accurately. Yet another advantage is that quieter rifles on ranges mean less public disturbance and better public relations for shooters – that’s good news.

More and more hunters are now using sound moderators or suppressors today than ever before and that is great. There are many on the market, but there are no industry standards and, while adverts tell you a lot, it’s often not what they tell you that’s important, but what they don’t tell you. Both Tim and I have been using MAE suppressors for a number of years and while they were initially heavier, being made of stainless steel, the latest versions are amazingly light and incredibly quiet.  For the more technically minded, or for those who have questions about suppressors, I have copied the following from the MAE website to answer some of your questions. Suppressors, by the way, will not affect the ballistics or the accuracy of your rifle. In fact, a suppressor may make it shoot more accurately.

How do moderators/suppressors work?

Moderators are instruments designed for reducing the sound signature of a gunshot with the emphasis on reducing the risk of hearing loss. As a shot is fired the precursor wave is the first to enter the moderator, followed by the projectile, then finally the blast wave, the main cause of hearing loss in shooters.

The recoil is generated by the combusting propellant, applying pressure to the rear of the projectile to gain the velocity required. As the projectile leaves the barrel it then passes into the blast baffle (Static Valve) which is one of the first components to come into operation.

The Blast Baffle serves three different purposes:

  1. It is designed to help strip the high pressure gases away from the projectile (which can influence its flight) leading to accuracy issues.
  2. The projectile partially seals the entrance to the blast baffle for a very short period of time (measured in milliseconds) allowing the blast wave/ gases to move rearward down inside the expansion chamber. This gives the projectile time to exit the moderator without the influence of the high pressure gas.
  3. The blast baffle also acts as the muzzle brake which almost simultaneously occurs as the projectile enters into the blast baffle. It is the high pressure of the blast wave acting in conjunction with the specific weight of the projectile which gives the felt recoil. This pressure wave is then transformed to work in the opposite direction and apply forward force onto the face of the baffle which pushes the firearm away from the shooter thus reducing the felt recoil.

As the projectile moves into the forward section of the moderator it enters the baffle stack which has two functions:

  1. The baffle stack helps to strip and deflect much of the precursor wave away from the path of the projectile.
  2. As the projectile exits the moderator the blast wave (which is moving at approximately 2-3 times the speed of the projectile) is temporarily redirected to the filling of the rear expansion chamber. As the gas starts to flow into the forward section of the moderator the blast wave is met with the baffle stack which then helps the gas to further expand and cool which dramatically reduces the energy in the gas and so reduces the sound pressure level.

Why MAE uses Stainless Steel

The internal workings of the MAE centre-fire moderators are permanently sealed and do not require disassembly for cleaning. The sealed units prevent incorrect disassembly and assembly of the components which can lead to misalignment causing bullet-strike and accuracy problems. We choose to craft all our centre-fire products using 100% 304L stainless steel. The reason being is that our centre-fire range of moderators cater for a wide variety of calibres and we wish to ensure all our valued customers are provided with a durable product. Our entire centre-fire rifle range of moderators does not incorporate dissimilar materials eg aluminium and stainless steel.
Moderators are in essence pressure vessels. They are similar to boilers, but on a smaller scale, dealing with the high pressure gases produced from a gunshot. In our experience, manufacturing moderators using both aluminium for reduced weight and stainless steel internal components to deal with the harsh exposure to combusting powder, creates multiple problems. It is generally accepted that all oxide-protected metals that have contact with dissimilar metals, especially in moist environments, should be avoided. The following are four good reasons why we use stainless steel. 

1: Galvanic Corrosion: Using aluminium and stainless steel together creates a galvanic reaction, similar to what occurs to make a wet battery work. This is a chemical reaction between two dissimilar metals. Metals have a galvanic rating which is a guideline in the combining of materials in manufacturing. The more positive the numbers for the relative metal the more noble the metal. The more noble the metal the more resistant it is to Galvanic Corrosion. Therefore putting aluminium and stainless steel together creates a reaction which compromises the structural integrity of the less noble metal, in this case the aluminium. To further prevent this reaction the aluminium components must be anodised or similarly treated to create a boundary layer between the two metals.

2: Thermal Expansion: When metals are subjected to heat e.g. gun shots, thermal expansion of the two dissimilar metals can lead to the components with a slower thermal expansion rate becoming loose in the assembly.  This allows the high pressure gases from the combustion to force residue into the gaps between the components created by this expansion. As the moderator cools, the exterior aluminium tube contracts and traps the residue which has lodged between the tube and the internals. For this reason, aluminium moderators must be able to be disassembled to allow access cleaning the internal components and removal of this residue. Either the front or rear caps, or both, must be unscrewed to gain access. The unscrewing of these caps and the removal of the internals, combined with the residue, eventually wears through the thin anodised layer on both the exterior tube thread and the end cap threads thus compromising the corrosive resistant properties of the aluminium and accelerating the galvanic reaction. With 100% 304L stainless steel, the expansion rate of the components is uniform thereby reducing the possibility of parts coming loose. As there are no dissimilar materials a galvanic reaction is obviated.

3: Flame-Cutting:  In our experience we have found that unlike aluminium, 304L stainless steel has good flame-cutting resistance. Flame-cutting results from the high temperature and high pressure generated from the burning propellant. We have found that flame-cutting will erode the inside of the aluminium tube directly where the high pressure gases are exiting the muzzle of the rifle barrel. Such erosion greatly reduces the life of the aluminium.

4: Bullet Strike: Over the years we have refined our products to ensure safety to the firearm operator, as well as to the bystander, in the event of bullet-strike inside the moderator. This does occur, albeit infrequently, and it is a very real problem. We have been improving our moderator design to mitigate the consequences should one happen. The machined internal components are designed to collapse and to project the flight of the bullet out the front of the moderator. The baffles forward of the blast baffle are made of lighter gauge stainless steel material than the exterior tubing therefore they present less resistance to the erratic flight of a bullet which has experienced a strike within the moderator. This is to ensure that the projectile does not compromise the exterior shell of the moderator and place the operator or bystander at risk. There are articles and images relating to products which have encountered bullet strike on our web site, www.mae.co.nz

Protecting your hearing isn’t an option if you are a hunter – it’s mandatory! Take it from someone who’s been on both sides of the fence: it’s not much fun losing some of your hearing. Buy a suppressor for hunting and get top quality hearing protection for your visits to the range.

A final comment: a brief discussion I had with an audiologist at the Sika Show in Taupo one year was quite revealing. She told me a good number of older hunters they tested were concerned with their hearing loss, for good reason, and a number of younger hunters tested also had some significant hearing loss. If you have any doubts about your hearing, get it checked. Protect one of your best hunting assets. Early prevention may prevent needless problems in the future and ensure you can keep hunting successfully for many great years!

Article used by permission of MAE  – see www.mae.co.nz

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concussive force 1

Concussive Force: The Silent Variable in Hearing Loss:

This type of damage is referred to as concussive damage, and it is the secret culprit causing so much damage to military personal and law enforcement officers.

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ARTICLE BY SEAN BELL AND SERGIE ALBINO ON JUN 16, 2014

The U. S. Army Center for Health Promotion and Preventive Medicine lists hearing loss from gunfire as the most common injury for soldiers, and the Department of Veteran Affairs says hearing damage is the number one disability claimed by returning vets. In addition, a study from the Department of Otolaryngology, National Taiwan University Hospital, Taipei, Taiwan, found that even with double ear protection, hearing loss still occurred in about 75 percent of those studied. It’s not melodramatic or overblown to claim hearing loss is disabling some of our most brave men and women.

Why is this such a problem? Everyone who has ever taken a gun to a range, either as a professional or amateur, knows you need to wear ear protection. However, research shows there could be more to protecting your hearing than just wearing the ear muffs or inserting the plugs (or both). First, how is hearing loss defined, and how does it happen?
The intensity or volume of sound is measured in decibels (dB). Without going into too much detail about decibels, understand that a whisper is about 30 dB, normal conversation would be 60 dB, an alarm clocks hit about 80 dB, and anything over 85 dB for an extended period of time can lead to permanent hearing damage. Over 140 dB for an impulse sound will do the same thing.

Almost all firearms (pistols, rifles, shotguns, etc.) start at 140 dB and can increase dramatically from there. This is why protection is so important. From the first shot fired you are already at the threshold that causes permanent, irreparable hearing loss.

All standard hearing protective devices on the market have a noise reduction rating (NRR). This number is not a one-to-one ratio, meaning a set of ear muffs with an NRR of 30 does not actually lower sound by 30 dB. You have to subtract 7 from the NRR and divide by 2. So a device with NRR 30 is actually only about a 12 dB deduction (30-7/2=11.5). If you are doubling up on both ear plugs and ear muffs, add 5 to the protection with the highest rating.

Now go grab whatever hearing protection you’ve been using. Do the math; subtract that number from 140. Is it below 80? If not then you’re damaging your hearing. But wait. You say, 140 dB is only for impact noises. I only shoot for a few minutes at a time, so my number is 80 dB. I say, nice try. If you’re in an environment where shooting is happening (shooting range, military situation, etc.) then you need to count all the time you’re there.

But here’s the kicker, this is something few people are aware of. Even if you get the best ear protection and then double up on both ear muffs and ear plugs, you still aren’t stopping the hidden danger of hearing loss through bone conduction. This is the area where traditional protection completely fails you.

Sound can be transmitted directly through the bones in your skull into your inner ear. Regular protection doesn’t stop this transmission of vibration and the skull only dampens between 40 dB to 60 dB of it. This type of damage is referred to as concussive damage, and it is the secret culprit causing so much damage to military personal and law enforcement officers. Unlike the average shooter, military and law enforcement personnel are far more likely to be involved in close-quarters combat. This means the concussive force from their firearms poses a much greater risk because of the close proximity.

To give you an idea of how prevalent hearing damage is, 60 percent of veterans returning from Iraq and Afghanistan are suffering from hearing loss. This amounted to $1.1 billion in disability payments in 2011. It’s not any better for police officers. In 2011 New York forced the retirement of police officers that wore hearing aids, many of whom needed hearing aids because of hearing loss received while working on the job.

How do we address this oversight in protection? Concussive damage is a little trickier to deal with than sound wave damage. One notable solution is a muzzle device. You want something specially designed to direct the concussive force of the shot away from the shooter and ideally force it parallel with the bullet. This means the sound and bullet are traveling in the same direction.

Understanding the different causes of hearing loss is the first step in keeping our military forces and police personnel safe. The second is making sure they are equipped with the proper education and tools to protect themselves.

Sean Bellis a freelance writer living in Florida. He received his B.A. in Interpersonal and Organizational Communication from the University of Central Florida. He has held several educational leadership positions and works closely with the health and wellness industry. Questions can be sent to sean@roughcutwriting.com.Sergie A. Albino is a blogger and CEO of IROC Tactical, a firearms accessory company aiming to improve the shooting experience. He invites to your comments at www.IROCTactical.com.

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