Hearing loss…. Prevention is better than Cure!

Noise is generally considered as unwanted sounds or excessive noise from many and varied sources including industrial operations, motor ways, airports, heavy earth- moving equipment, shooting ranges, music concerts, to name a few. These all produce sound levels which exceed noise level standards on occasion. Sound can be defined as any pressure variation that the human ear can detect. However there are Noise at Work Requirements that specify the amount of sound that the ear may be subjected to before permanent and irreparable damage will occur. The threshold for pain is 140 dB. One shot from a firearm will exceed the safe limit for the ear.

Why do shooters suffer hearing loss?

From the trigger being depressed through to the ear-splitting crack of a gunshot, (certainly more noticeable on a range however than in the bush) hearing loss is inescapable and for the ear, an irreparable problem.

From the moment the firing pin/ striker impacts the primer to the igniting powder sending the projectile on its journey up the bore there is a pressure wave forming in front of the projectile. This is known as the precursor wave or bow wave. This is created by the accelerating projectile displacing the air forward of the projectile in the bore.

As the pressure in the chamber intensifies, another pressure wave is being formed by the burning propellant. This pressure wave is gaining velocity at approximately 2-3 times faster than the terminal velocity of the projectile.
Once the projectile leaves the bore the high pressure gas behind the projectile, which is known as the blast wave, (likened to popping the cork off a wine bottle) is released.

It is the release of this wave that creates the ear-splitting sound of the gun shot, and it is the effect of this secondary pressure wave that moderators are designed to Mitigate.

Can I use ear-muffs or ear-plugs?

Correctly-graded ear-muffs and correctly fitted ear-plugs will reduce the risk of hearing-loss, but not nearly as effectively as a good moderator.
Following are the reasons;
1. In most cases during recoil the comb on the rifle stock impacts the ear-muff, which increases the sound level pressure to the ear therefore negating the effectiveness of the ear-muff. The recoil from a large calibre rifle can also shift the position and break the seal around the ear of the shooter.

2. The human body is made up of approximately 70% water, and the recoil which is produced during firing sends a pressure wave through the body at approximately 1558 m/ sec. A firearm being discharged from the shoulder is a very short distance to the ear drum therefore damage to the ear drum is inevitable.
Nor can the combination of ear-plugs worn under ear-muffs suppress this pressure wave.

3. When hunting/ deer stalking, the use of ear-plugs or ear-muffs can and will impair the hunter’s hearing. You cannot hear where your hunting companion is, nor be fully aware of what is happening around you. Also it makes it very difficult to completely identify your target species.

Why Moderators are more effective than ear-muffs or ear-plugs

1. Moderators are attached to the firearm and act directly on the Sound Pressure Level created during firing.

2. Moderators have integral muzzle brakes which remove a high percentage of the felt recoil. The weight of a moderator also plays an important part with recoil reduction.  Extra weight can be advantageous. Too light can result in next to no recoil reduction on heavier recoiling calibres, which will allow harmonic/ vibration transfer through the body.
A moderator also minimises the chances of the hunter flinching which is one of the main reasons for lost or wounded game.

3. Moderators allow the shooter or hunter to clearly hear as well as being aware of what is happening around them and under-foot.

4. Moderators stop “muzzle jump” which allows a hunter taking long shots to determine where the projectile will land and to allow for calculated shot placement, thus reducing the chance of lost or wounded game.

5. Moderators reduce the risk of unwanted attention from neighbouring property owners whilst shooting e.g. farm or range.

6. Moderators reduce stress and the risk of hearing injury whilst shooting over dogs or around livestock.

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 caters 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.

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 this 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 eg gun shots, thermal expansion of the two dissimilar metals leads to the components with a slower thermal expansion rate to become 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 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 its consequences, in the event of a bullet strike. 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. Refer to articles to read and view images relating to products which have encountered bullet strike.

THE “HOW TO” OF DEER HUNTING IN NZ with Alex & Tim Gale

Learn how to hunt deer and up skill your hunting knowledge.

This DVD takes you into the outdoors and shows you step by step the ‘how to’ of deer hunting. It’s the next best thing to being there.

You’ll learn about:

The NZ deer species
How to be a safe hunter
How to shoot a rifle and sight it in correctly
Trajectory of bullets
The right clothing and gear to take
Tips on stalking
Vital areas of deer
How to gut and carry out deer
How to butcher your animals
What resources are available….. and much more.

All designed to help you become a safe and successful hunter.

Alex Gale is the author of four hunting books, including the widely acclaimed “The New Zealand Deer hunter’s handbook”. He was also a hunting guide specialising in hunter training. Both he and Tim have been professional hunters and love seeing other people learn to hunt and enjoy what our fantastic outdoors has to offer.

To Purchase: http://www.nzhuntingexp.co.nz 

Produced by: Alex / http://www.nzhuntingexp.co.nz 
Camera & Editing: Simon Oliver
Directed by: Simon Oliver