The Basics of Sound Moderators
A sound moderator, also sometimes referred to as a suppressor or silencer, is an accessory that dulls the sound emitted from a firearm.
Upon firing; several sounds will occur. The initial audible sound is a combination of the primer, the ignition of the powder and the supersonic crack. A proportion of this sound will transfer through the steel of the barrel, the rest will then be expelled from the barrel where the moderator now does its job in reducing the sound as much as possible and then the sonic crack of the bullet breaking the sound barrier. Many factors will influence noise reduction including; calibre, barrel length, barrel diameter, ammunition used, the weather, atmospheric conditions, the location and even the surroundings of which sound will reflect off.
The Supersonic Barrier
When a bullet breaks the sound barrier a sonic boom occurs which is also known as a sonic crack. The speed of sound is generally around 1100 feet per second, although this can vary due to factors such as temperature, humidity, and barometric pressure. This supersonic crack cannot be avoided with high-velocity ammunition. The only way to eliminate this is by launching a bullet at slow speeds below the sound barrier and this is known as a subsonic shot.
Preventing Hearing damage
Typically, hearing damage can occur from long exposure to noise at 80-85 decibels. At 110 decibels, hearing damage starts to occur within two minutes of exposure. A rifle without a sound moderator can be more than 150 decibels, to put that into perspective a jet taking off is around 150 decibels and loud enough to cause eardrum rupture.
Across several different tests using many moderators of varying designs and manufactures, significant reductions in decibels are present, making a noticeable difference. However, results all showed the moderated centrefire rifles were still recorded at 110 decibels or higher. So, regardless of how many shots you’re planning, it’s still recommended to wear hearing protection.
Performance, durability, weight, and cost are all key considerations when selecting a moderator. It’s important to choose a moderator which suits your needs, as everyone has different preferences. Not everyone has the same criteria, for example; a shooter carrying rifles in field situations require a lightweight set-up with reduced noise and are only subject to small quantities of shots. In comparison; a shooter on a range would be more suited to a heavier, larger, high-volume moderator which will potentially maximise recoil reduction and will be made using materials capable of withstanding a high quantity of shots.
As a general rule, but not exclusively; a smaller light-weight moderator made from aluminium will weigh less, but will be less durable when a high quantity of shots is needed, compared to one made solely in stainless-steel. On the other hand, the stainless-steel moderator would be a lot heavier and more expensive. A lighter alternative to stainless-steel could be to use materials such as Titanium, but then costs would be even higher. Many moderators are now made using a mix of materials which are specifically used for certain parts, based on the properties needed and best suited to that purpose.
It’s important to note that the internal volume of the moderator has a significant impact on noise and recoil reduction. There is a minimum safe requirement of moderator size based on certain calibres and quantities of powder being burnt, likewise, an excessively large moderator for a small cartridge with small charges of powder will be past the optimum length, and as a result, there won’t be enough pressure within the moderator to make it work efficiently. This leaves you carrying excess weight and size with no additional benefits. For an accurate guide to choosing the right moderator for your application, please take a look at our ‘How to Choose a Moderator Chart’.
Modular versus Sealed Moderators
Something to remember is that the barrel and the core of a sound moderator are the two parts most exposed to wear and tear. These two parts should be treated much like the brakes on a car; over time they will wear and eventually they will need replacing. Which brings us on to sealed units versus modular moderators.
Sealed moderators do have some advantages, they offer a reduced chance of concentricity issues, however, these units can’t be cleaned and wearing parts can’t be replaced. Should there be an issue, it would mean replacing the whole unit and this can be expensive.
A modular design allows you to replace any wearing parts when the time comes, at a fraction of the cost of a complete unit. A modular design also allows for different thread and calibre sections to be used, enabling you to use it across multiple rifles. Also, note that by changing the calibre specific part to the calibre used will maximise the potential decibel reduction.
For another view on moderator considerations, check out this article by Fieldsports Journal.
Front Mounted versus Over-Barrel Moderators
A front-mounted moderator has some advantages, it can be used on short barrels or rifles which have long extended forends or handguards. Another advantage is; because the moderator and barrel heat up, having the moderator in front of the barrel enables the heat within the barrel to dissipate faster. Unfortunately, A front-mounted moderator can add considerable length and weight, making the whole firearm long, unbalanced, and awkward especially in some hunting or field situations. This is where the over barrel design helps by offsetting some of the moderator length back over the barrel there for reducing the total length of the firearm and improving balance.
Over-barrel moderators also give the opportunity for the end-user to use larger higher volume moderators and on some rifles that would normally prevent them from having a compact setup. The ability to bring the expansion chamber back over the barrel helps boost the internal volume and improve performance in terms of noise and recoil reduction on a compact setup.
So, there you have it - a brief guide to some of the key consideration regarding moderators and their designs. Now check out our line-up of moderators.