Rifle silencers – how do they measure up?
Hunters and competition shooters often ask which of the l ocally manufactured rifle silencers perform the best. We at Helber decided to run a little test and invite local manufacturers to submit their products for testing. Please note that Helber is in no way connected to any of the silencer manufacturers/ suppliers.
The great South African silencer test was held on 13 December 2014 at the Blue Gum Valley Shooting Range near Bapsfontein and we tested 27 silencers on the day. Our
aim was to involve as many of our local manufacturers as possible.
We used two rifles, a singleshot CVA Apex in .243 Win fitted with a sponsored Tactical T1 624x50 Rudolph scope (with T3 reticle) and a Winchester Model 70 in .338 Win Mag. The latter fitted with a Nikon Long Range SF 832x50 scope. Talley scope mounts were used on both rifles and the ammo was loaded by Titan. For the .243 rifle, Titan used 73gr bullets and for the .338 Win Mag, 204 grainers. The primers were Sellier & Bellot and Titan used our local S365 propellant.
Before I give feedback on the test, let’s look at some technical aspects of silencers.
WHY FIT A SILENCER?
For obvious reasons hunters rarely use hearing protection when they hunt. Unfortunately unsuppressed gunfire from hunting rifles is loud enough to cause permanent hearing loss. Prevention is better than cure they say, so using a silencerequipped rifle will protect the hearing of the hunter, PH and the trackers. Silencers also reduce recoil and muzzle flip and due to the decrease in recoil such rifles are more comfortable to shoot.
They are thus ideal for the training of youngsters, women or anyone that is recoilshy.
A more pleasant shooting experience prevents the shooter from flinching and ultimately contributes to accurate shooting, which reduces the possibility of wounding shots and thus translates into more humane hunting. Reducing the muzzle flip of a firearm also allows the shooter to fire followup shots quicker – an important benefit when backup shots are needed in a hurry.
HOW IT WORKS
It is important to realise that a silencer/suppressor can only reduce the sound of the muzzle blast. It cannot silence the sonic crack of a highvelocity bullet breaking through the sound barrier (any bullet travelling faster than 1 040fps will break the sound barrier) and it will not reduce the noise of a cycling action of a semiauto pistol or rifle. Sonic cracks that highvelocity bullets produce can be quite loud.
The only way to silence any firearm with good effect is not to use a semiauto and to use subsonic ammunition.
Depending on the calibre and/or load an unsuppressed rifle produces noise levels of 165 to 170 decibels (dB) and silencers reduce those noise levels by about 20 to 30dB.
A silencer works very much like a car’s muffler. It contains and dissipates the hot expand ing gasses that exit the rifle’s barrel. Firearm silencers/suppressors work by lowering the pressure at the point where the expanding gas is vented into the atmosphere. Suppressor baffles provide a large surface area to cool and condense the gas, lowering its pressure. The more baffles a silencer have, the better the sound reduction. Each doubling of the number of baffles (say from 4 to 8 or from 8 to 16) reduces the muzzle blast noise by approximately 3dB (usually 2 to 5dB).
The baffle plates inside the silencer retain or partially block the pressure and shock waves and if designed correctly, it reduces the recoil by having an opposite direction of force of the recoil. This “muffling action” increases the heat within the silencer and produces quite high pressures. Therefore silencers must be able to handle very high pressure otherwise they will rupture.
BAFFLE HOLE DIAMETER
Standard baffle apertures are 7.5mm, 8.5mm, 10.5mm and 13.0mm. As a rule, the hole must be the size of the bullet’s calibre plus at least one millimetre. Normally manufacturers use a 7.5mm hole for .22 centrefire and 6mm calibres. An 8.5mm hole is used for 6.5mm .270, 7mm and .308calibres, while a 10.5mm is used for the .338s and 9.3calibres. For calibres such as the .45s a 13mm hole is used.
The smaller the baffle hole diameter, the more effective the sound suppression. It is always better to add more baffles than risk making the baffle holes too small. All rifle bullets yaw a little on leaving the muzzle. The longer the bullet the more baffle hole clearance is needed to accommodate the yawing effect without risk of a bullet grazing a baffle. Bullets that touch the side of a baffle on the way out will obviously deflect and affect accuracy.
TYPE OF SILENCERS
The most common types are the reflex suppressors (a reflex suppressor extends behind the muzzle and supports itself at two points on the barrel) integrated silencers (that cover the whole barrel) and the “standard” types that screw onto the muzzle end of a rifle barrel. Standard silencers are the most popular ones with hunters/ shooters all over the world.
MAINTENANCE
Silencers are usually manufactured of steel or aluminium, or both materials and require little maintenance. It is advisable to clean them after each shooting session though. Remove the suppressor from the barrel or leave the action of the rifle open »
» after use. This prevents corrosion by allowing condensation that might have formed inside the rifle barrel and/or silencer to evaporate. A small amount of light oil, sprayed into the suppressor, will prevent corrosion. Normal carbon fouling from powder does not have an effect on the suppressor’s functioning, but fouling will build up inside the silencer over time and eventually needs to be removed.
Loose grit and carbon dirt are easily removed by shaking the suppressor, while holding it in a vertical position. Pouring liquid soap or solvents into the silencer to wash the inside out, is not advisable.
interesting facts
As mentioned earlier, no silencer can muffle the supersonic crack of a bullet. Silencers will muffle a rifle’s report with about 20 to 30dB and recoil by about 20 to 40%.
A silencer will always change a bullet’s point of impact due to the weight it adds to a barrel, the fact that it eliminates muzzle flip to a certain extent and because it changes the barrel dynamics/harmonics. The bigger and heavier the silencer is, the more dramatic the effect. On average bullet velocities increase when silencers are being used. Silencers trap the heat of the expanding gasses and become hot very quickly, so handle with care (no bare hands after a number of shots). Ultimately you want the silencer to trap the heat and not transfer it to the rifle barrel.
silencer fitMent
Precise fitment is critical for the optimum and save performance of a silencer. Incorrect fitment and/or manufacturing can cause serious damage to a rifle or harm the shooter (or any spectators that happen to be around).
silencer shoot out
Before the test started the rifles were zeroed at 100m without the silencers. Then we fired three shots per rifle with each of the silencers attached and measured the noise levels. That was done from a safe angle about 60 degrees behind the shooter. The highest reading (decibels) were used as data. Ideally, sound readings should have been taken at various angles from the shooter, »
» because of the internal design differences of the various products (with some silencers the noise levels may differ at certain angles). Unfortunately we did not have the time to do that.
We recorded the following data on all the silencers: Weight, length, diameter, the effect of heat transfer on the silencer and the barrel, the decibel (noise) readings with and without a silencer, bullet point of impact and bullet velocities with and without the silencers fitted to the rifles.
With the silencers fitted, the rifles printed 150 to 250mm lower at 100m. Bullet velocities increased with all silencers, but was slightly higher with the .243 Win than the .338 Win Mag. On average accuracy was better with the silencers fitted, but there were cases where fitting a silencer actually affected the accuracy of the test rifles. All of the test models obviously reduced the felt recoil of the rifles.
A silencer that blocks too much of the gasses, transfers the heat to the barrel, which is undesirable – the heat should be transferred to the silencer. The bigger the back pressure of the gasses in the silencer the bigger the recoil reduction, but not necessary the muffling of the sound. When firing shots in quick succession the first one quite often produces less noise than the following shots. So, when using a silencer, give it time to “breathe” between shots to maximise the muffling effect. After ejecting the case, do not chamber a round right away, leave the bolt open to allow the barrel and action to breathe.
Because there are so many variables involved it is almost impossible to pick a winner. Instead, we decided to capture the result on a spread sheet for your perusal (See accompanying table). Shooters’ requirements and their reasons for fitting silencers differ. Silencers that provide very good sound reduction are out of necessity bigger and heavier.
Work through the data and pick the silencer that will fit your requirements.
conclusion
So, would I fit a silencer to one of my rifles? Yes for sure, on all my rifles. • For more details please contact me at
bernard@helber.co.za.