Click one of our Frequently Asked Questions below to read in full:

1
What do sound suppressors do?

There are four noises which make up the “boom” one hears when shooting a firearm. The first is the action noise (i.e.: the hammer hitting the firing pin, the slide/bolt cycling, gas escaping though the ejection port). The second is the bullet flight noise. If the projectile travels faster than the speed of sound, which is approximately 1050fps, there will be an audible “crack” heard by the shooter. The third is the bullet striking the target. The last noise associated with the firing of a firearm is the combustion noise hitting the atmosphere when the projectile leaves the barrel. The propellant gases that pushed the projectile from the barrel are going faster than the speed of sound and typically still burning. The “boom” of the gasses hitting the atmosphere is typically louder than the other noises, which is why the boom generally is all the shooter and those near the shooter hear.

Firearm silencers work in the same manner as mufflers for cars and lawn mowers. Both provide a controlled environment in which the gasses can expand and cool before exiting into the air with less energy and noise. A typical silencer has a casing segregated into chambers by partitions called baffles. Each baffle has a passage through which a projectile can pass. When the host weapon is fired, the projectile exits the barrel and passes through the length of the silencer, but the gases that propel the projectile expand into the baffled chambers where they are temporarily trapped. When they do find their way out of the silencer, the gases have slowed considerably and thus produce less sound.

2
What are sound suppressors used for?

Silencers are “hearing protection” that attaches to your firearm, not unlike a muffler on an automobile.

OSH limits impulsive or impact noise at 140dB peak sound pressure. “Hearing Safe” in the Firearms Industry refers to a gunshot that produces less than 140dB peak pressure. By way of comparison, a 1911 45ACP pistol or a 16” .223Rem rifle produce approximately 165dB peak sound pressure. Decibels are logarithmic, meaning that sound pressure doubles or halves approximately every three decibels you increase or decrease the sound.

For recreational shooting, it’s acceptable to wear hearing protection which will block out a portion of the noise produced from shooting firearms. However, this is not always an option for Military, Law Enforcement or hunters. As a result, with every shot these individuals are producing noise that can not only permanently damage their own hearing, but those of individuals around them.

Although silencers cannot muffle every noise that is associated with the discharge of a firearm, they can greatly reduce some aspects of the process. Silencers primarily reduce the noises associated with “muzzle blast,” by providing the escaping gases baffled chambers in which to expand and depressurize prior to escaping the silencer.

3
Who would want to use a sound suppressor and why?

A silenced firearm is eminently more enjoyable to shoot than one without a silencer. Silencers generally increase the accuracy of a host firearm while reducing recoil and eliminating a significant amount of the muzzle signature. Shooters are able to concentrate more on breath control and trigger pull when they are not subjected to the fatigue and distraction of a deafening and bright muzzle report. Beginner shooters are typically not so intimidated when introduced to the shooting sports with a suppressed firearm. They are able to easily hear instructions given to them by trainers because the report of a host firearm is reduced to below the OSH guideline level for hearing damage. Suppressed firearms are also less likely to disturb people, livestock, or wildlife that may be in close proximity to where you shoot.

4
What are the basic parts of a suppressor and what does each part do?

All silencers feature an expansion or blast chamber that the bullet must travel through before making its way through each subsequent baffle and eventually exiting the silencer. The expansion chamber is generally the chamber with the largest volume within the silencer to allow for the initial introduction of the hot expanding gases propelling the bullet. These hot expanding gases eventually make their way through the baffle stack consisting of a designated number of baffles and spacers, which are essentially smaller chambers designed to disrupt the natural path the gas would take. By the time the gases exit the silencer, they have slowed considerably and produce a quieter sound signature.

5
How do integral flash hiders or muzzle brakes affect suppressor performance?

Both flash hiders and muzzle brakes can be used to provide a solid mounting point for silencers to attach to. Flash hiders have no negative effect on the silencer, but muzzle brakes can actually extend the serviceable life of your suppressor. The blast chambers on our internal muzzle brake/diffuser act as a sacrificial blast baffle and can take the brunt of the weapon’s muzzle blast. There is no sound difference between flash hiders, muzzle brakes or flash suppressing muzzle brakes when used inside a suppressor.

6
I sometimes see different length suppressors for the same application. Does length affect sound suppressor effectiveness?

Length and volume affect sound, but there is a point of diminishing returns. At SileNZ™ we are striving to achieve better levels of sound level reduction in shorter silencers. Through constant research and development, superior material selection, and improved baffle design, we hope to achieve our goals of continuing to offer the best lighter weight suppressors on the market.

7
How does the heat generated from firing a gun affect the suppressor?

The hot expanding gases that propel the projectile are trapped within the silencer and cause the temperature of the silencer to increase. The more intense your firing schedule, the hotter the silencer (and the barrel) will become. Higher pressure rounds also lead to higher temperatures within the silencer because of the amount of hot expanding gases that the silencer will trap.

8
What kind of lifespan can I expect from your suppressors?

With all silencers, lifespan is determined by several factors, including calibre, barrel length, muzzle device, and firing schedule, so there is no definitive answer regarding lifespan. SileNZ™-Hybrid™ suppressors will typically outlast similar sized alloy-only suppressors by a comparative shot count of approximately 3-5 times. Centrefire suppressors should easily withstand several thousand rounds, provided they are not used on large magnum calibres, or very short barrels. Keeping your barrel at the longest practical length possible will provide better noise suppression and longer service life for the suppressor.

9
Can your suppressors be maintained for longevity? If so, how do I do it?

Due to the inherently dirty nature of rimfire ammunition, silencers trap much of the unburned powder, lead, and filler that would otherwise be expelled out of the barrel and into the atmosphere. As such, rimfire silencers should be cleaned on a regular basis. See our recommended cleaning guidelines in the ‘Support’ section of this website.

Centerfire rifle silencers typically utilise fully welded or sealed designs, and are traditionally cleaned by a solvent bath. In most cases centre-fire suppressors can be considered to be essentially self-cleaning, unless you are firing over 5000 rounds in which case carbon build-up may become an issue. SileNZ™ centrefire suppressors are able to be dismantled and rebuilt by factory-authorised warranty agent only. Do not attempt to dismantle them yourself.

10
What kind of cycling issues might I have with using a suppressor?

Rimfire or Centerfire suppressors when used with locking breach systems, like bolt or break open rifles are typically issue free.

For semi-auto rimfire rifles, fitting a suppressor will increase gas blow-back pressure to some degree, and this can result in an increase in gas-spit (or blow-back) from the action port as the bolt cycles. This can be of particular concern and danger if a left-handed shooter is shooting a semi-auto RH rimfire rifle. Protective shooting/safety glasses may need to be worn to reduce the chance of eye irritation or damage.

For centre-fire rifles, the fitting of a suppressor can increase the back-pressure of the rifles operating system CONSIDERABLY causing an increase in the peak chamber pressure dwell time, which can result in over-vigorous extraction of fired cases, increased rearward bolt thrust, and additional forces on the extractor and other parts. Some semi-auto centerfire rifles (such as Browning BAR, and others) may be prone to jamming upon firing if the increased gas back-pressure is not regulated back to a safe level and softer function with an adjustable gas block system, or other similar modifications. As these (and other) circumstances are beyond our control, for liability reasons we do not recommend our suppressors to be fitted to any centerfire semi-auto rifles.

If you own an AR-15 type rifle with an adjustable gas-block system and want to fit and use one of our suppressors – that’s fine, however if you do so you will be assuming full risk. Due to the possibility of such a weapon being used for rapid-fire, extreme-duty (over-heat) situations, we will consider any warranty cover for the suppressor to be void.

11
Does ammunition choice affect sound output? What are subsonic rounds?

Subsonic” means that when the projectile leaves the barrel of the firearm, it is traveling under the speed of sound, which is approximately 1050fps (330 metres/sec).

Rounds traveling over 1050fps will break the sound barrier, creating a sonic crack that typically will be louder than the suppressed gunshot.

In rimfire, the catalogued velocities are based on a rifle length barrel. The longer the barrel, typically, the more effect the propellant gases have on the round. That means that most “standard velocity” or “target” ammunition will remain under the speed of sound out of a handgun. However, in rimfire rifles, a round that would have remained under the speed of sound in a handgun may make the round cross over the 1050fps threshold, creating a sonic crack. The noise associated with supersonic velocity ammunition, especially in rimfire hosts, can be louder than the suppressed shot. Typically, rimfire rifles will require ammunition labelled as “subsonic” for the projectile to actually remain subsonic.

The vast majority of centerfire rifle rounds are designed to travel well over 1050fps. As mentioned earlier, there are specialty subsonic type loadings in centerfire rifle calibres. . 300 AAC Blackout, which is a SAAMI approved round, is one such cartridge. It was specifically designed with both subsonic and supersonic use in mind.

Another issue with subsonic/heavier projectile use can be barrel twist. The vast majority of consumer grade firearms are designed by companies to stabilize projectiles within certain “common” bullet weights and going outside that design parameter can cause stability issues for projectiles. “Stability issues” may cause end cap strikes and decrease accuracy (with or without a silencer). Stabilization is another common issue with subsonic .30cal projectiles, which typically run in the 220gr range. These length projectiles need faster twist rates, like 1/10” or faster to stabilize. A consumer wanting to use subsonic ammunition with their host firearm should check with the ammunition manufacturer if they are unsure of their host/twist/ammunition combination.

12
How much sound can I expect to reduce from my gun?

There is a bit of a technical description of Decibels in the answer for question #2. To recap, an increase or decrease by three decibels will basically double or half the amount of sound. By way of example there, a 16” .223Rem AR15 type rifle is approximately 165dB, a 10” .223Rem AR type rifle is approximately 168db, or roughly twice as loud as the 16” rifle, all factors otherwise being equal. We went over that there are four sounds that occur, with the combustion noises being the loudest of the noises. The aim of any centerfire suppressor manufacturer is to try to get the sound signature down to (or below) the 140dB level. The simpler answer is that with the use of a quality made suppressor, you will be able to shoot your firearm with reduced risk of doing permanent hearing damage to you, your friends, your children, or your hunting dogs.

13
What are the pros to using a sound suppressor?

Silencers protect the shooter and those nearby from temporary hearing threshold shift and from irreversible hearing loss, which can result from single shot exposure.

When used on rifles, silencers generally improve accuracy by promoting the harmonic stabilization of the barrel and reducing gas-induced instability as the bullet exits the muzzle.

Silencers prevent “blooming” of night vision equipment and help preserve unaided night vision by eliminating muzzle flash.

Silencers reduce recoil and muzzle flip allowing for more accurate and faster follow-up shots.

Silencers disguise the location of the shooter by reducing muzzle flash and minimizing environmental disturbances.

Silencers improve training scores by minimizing recoil and muzzle blast and allowing the instructor’s commands to be clearly heard.

14
What are the cons to using a sound suppressor?

Silencers inevitably add length and weight to the host weapon system, which is unavoidable, but less than ideal. Through our research and development, superior material selection, and improved baffle designs, SileNZ™ suppressors are now able to be made smaller and lighter and more compact, but just as effective as products of the past. Most centerfire suppressors do require a baffle section extending at least 4” ahead of the muzzle to be reasonably effective, but 6” (or more) will usually work better.

Care must be taken to not over-heat aluminium alloy (centrefire) silencers in particular, and the heat mirage generated from firing an excessive number of shots in a short space of time may cause sighting issues or other problems until the silencer cools down again.

Suppressors also retain moisture and ammonia (and other gases) as a result of firing, and as such should not be stored permanently on the barrel, or for prolonged periods, as this may promote rust in the bore or muzzle areas of the host rifle barrel. Always remove the suppressor from the rifle when not in use, and store it in a well-ventilated open area to air out. Regularly applying grease to the muzzle threads is recommended.

15
What is First Round Pop (FRP)?

First Round Pop is a phenomenon in which the first round fired through a cold suppressor is louder than the subsequent shots fired. This is caused by the combustion of oxygen within the suppressor. After the first round is fired, the oxygen is burned up and replaced by combustion gasses. If the suppressor is allowed to cool for a short period of time (minutes) the FRP will occur again. Some suppressor designs are very effective at reducing or eliminating FRP. We normally notice a slight flash from the suppressor exit hole when the very first shot is fired through a brand-new suppressor. After this the unit settles down, especially once a bit of fouling accumulates in the suppressor.

16
Mono-core or stack-baffle system - what is best?

Both methods of manufacture have their own pros and cons, and both methods can produce very good, functional suppressors.

Mono-Core units are machined from a solid billet of a particular metal, and while being made as one solid part (instead of an assembly of smaller parts) they can result in a lot of wasted metal which is machined out. They may also require very long drills, and expensive machines (or machining techniques) to manufacture. Steel mono-core units can be strong, but very heavy. Aluminium mono-core units may be much lighter, but will not last as long as steel or stainless equivalents. Hard-Anodising can help to provide a hard surface, but even this can be eroded by the severe heat and blasting effects of the propellant gas – especially on shortened rifle barrels – which then leaves the aluminium core exposed to corrosion and/or cracking. Mono-core systems are a good choice for lower-pressure suppressors that may need to be pulled apart regularly for cleaning (i.e. for .22 rimfire rifles, or for pistols firing lead bullets.) For centerfire suppressors which will usually never be pulled apart, there is very little practical difference between ‘mono-core’ and ‘stack-baffle’ from a functionality point of view.

Stack-baffle system (such as common K-baffle, M-baffle, etc.) arrangements can usually be more efficiently manufactured, and may even provide a better level of sound suppression compared with some mono-core designs. The ability to use harder/heavier materials in the areas where it is needed is a significant plus for the stack-baffle system suppressor, with the option of using lighter materials in the less critical (or less stressed) areas. If the unit is not designed to be regularly field-dismantled, then a stack-baffle system can be a good option, especially for a centerfire suppressor.

SileNZ™, after consultation with various experts, have decided to produce both types of suppressor. We produce a mono-core design for our rimfire suppressors, and our own version of a stack-baffle system for our centerfire suppressors. We feel that these are the best choices for each particular application.

17
Barrel length - how short is too short?

Kaimai® does not recommend the use of barrels shorter than 16” in calibres from .223Rem to .30/06Spr, if used in conjunction with our suppressors. Damage to centerfire suppressors used on barrels shorter than 16" with factory (or reloaded) cartridges is not covered under warranty. There are three primary reasons for this:

Stability: Very short barrels may not impart enough spin on the projectile to properly stabilize it during the critical first few inches of flight as it passes through the suppressor. While the bullet may stabilize downrange suitably to be accurate when shooting unsuppressed, it may not stabilize sufficiently and could strike baffles when a suppressor is mounted. Some barrels with a faster rifling twist rate may overcome this problem though.

Velocity: The .223Rem cartridge (for example) is also very velocity dependent for stability. Very short barrels, less than 10.3" do not allow sufficient velocity to properly stabilize the round, thereby exacerbating the stability problem described above.

Erosion: The .223Rem cartridge was designed to burn its powder in a 20" service rifle. The maximum flame temperature and pressure happen at around 7" from the chamber. Short barrels under 10.3" cause excessive flame temperature and pressure within the entrance chamber of the suppressor. This causes excessive erosion of the blast baffle because hot, high pressure particles of unburnt powder ‘sandblast’ this baffle. So, provided you are lucky enough to avoid a baffle strike due the above two issues, the suppressor may be worn out in a very short period of time due to erosion. Due to the Hybrid™ design features of Kaimai® centerfire suppressors though, they will significantly outlast very lightweight ‘alloy-only’ suppressors, which could show severe baffle erosion within only 200 rounds, and in some cases complete failure of the unit in as early as 800 rounds may occur.

Pressure: As the barrel length is reduced, the pressure within the suppressor increases. For liability reasons, a 16" (centerfire) barrel is the minimum barrel length that we require to maintain an adequate safety factor and prevent any damage or premature wear to the suppressor, or injury to the user. Although a few inches of barrel doesn't seem like it would make much difference, it really does. By way of example, the exit pressure at the muzzle of a (milspec .223Rem) 7" barrel is almost 70% higher than that of a 10.3" barrel.
Kaimai® will not extend warranty cover to any centerfire suppressor which has been fitted to a rifle with a barrel shorter than 16”. Our recommendation is to leave the barrel as long as practically possible for your application.

18
Can I shoot my suppressor 'wet'?

No. A centerfire rifle suppressor should never be shot "wet". Using liquid inside the suppressor reduces the available volume for gas expansion, and can create other problems. The addition of (an unknown quantity of) liquid may increase the pressure and could cause the suppressor to bulge or burst, which could possibly injure or kill the shooter or bystanders. Centerfire rifle suppressors have much higher internal pressures than rimfire or pistol calibre suppressors. If the suppressor becomes submerged, allow the unit to fully drain before shooting.

Tests have shown that the addition of liquids (or grease) into a suppressor can help to reduce FRP and to aid in gas cooling, to some degree. However, the risks of water or oil running back down a barrel and/or into the action may cause irreparable damage if the rifle is subsequently fired in this condition. In short, SileNZ™ suppressors are designed to be run dry only. DO NOT shoot them ‘wet’.