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Problems with suppressors

januari 25, 2014
Some time back I started recognize some problems when using suppressors on my rifles. After some talks with my frieds we realised that we all had the same issues when shooting with a suppressor.
Isolating problems when using suppressors

Isolating problems when using suppressors

First of all we realized that we had a problem with a shift of POI. That problem is easy to address and compensate for, it’s the same all the time.
Green = Light Muzzle Brake, Brown = Our Magnum Brake, Black = Suppressor.

This picture shows the shift of POI at 100m using different brakes and suppressor.

This picture shows the shift of POI at 100m using different brakes and a suppressor.

Next up was all the mirage issues that made it hard for us to shoot more than 3-4 rounds without getting a problem with sight picture on warm days. This is especially a problem when shooting high pressure rounds such as 7mmRM, .300 WM and 338 LM. When looking at mirage problems it’s acctually two type of problems. One is the mirage from heat emission from the hot cylinder (suppressor). Thats acctually not the biggest problem, the main problem is the heated gases that slowly exits from the suppressor. When the suppressor gets hot it heats the air and gases inside, it expands and leaves the suppressor. When it leaves the suppressor thru the exit it goes straight up and into the line of sight. This problem is also possibly to address with the same principle as using a mirage shield over the barrel. Most mirage shields are straight angled, personally I  got better success with a slight v-shape.

Next problem is the muzzle velocity variation when shooting both with and without suppressor and also because of the freebore boost. The first speed change (suppressor often gives a higher muzzle velocity) is easy to adjust for with a chrono but the freebore boost is harder to address. There’s a lot of information about this subject to find on the internet. One  of those site is the https://www.tactical-officer.com/articles/chasing-the-truth-about-supressors-and-accuracy/#.UuOA23nnPu0

Shooting thru chrono to monitor muzzle velocity before addressing really long range!

Shooting thru chrono to monitor muzzle velocity before addressing really long range!

When freebore boost kicks in there is a quite lots of variables that comes into play. Cold suppressor is not effected as much as a hot so when the suppressor gets to a specific temperature the effects kicks in. You will  see this effect when you shoot thru a chrono on a cold day. First you get equal speed for a couple of rounds then the speed starts to increase. Look at the velocities at the first picture above and you will se a typical example of  this effect. To make it more complex, there’s a lot of variables. Amount of powder burnt when bullet exit the barrel, that is lower burn rate powder combined with a shorter barrel length will increase the effect. Suppressor designs, outside temperatur and muzzle pressure will likely also affect the amount of freeboore boost. The effect can be all from no effect to about 7m/s between shots.

Find more info about freebore effect on: http://emptormaven.com/2007/03/freebore-boost-effects/

Our conclusion, about freebore boost, is that this effect means little when shooting short and medium range targets but when shooting long range targets is’t really hard to address. No easy way to compensate for the effect. The two things to do is never shoot thru a hot suppressor or shoot without.

The latest problem I started to see is that the first round,  and sometimes also second round, always was of the rest of the group.

First rounds problem when using suppressor

First rounds problem when using suppressor at 100m

Problems with suppressor

First round problem when shooting with suppressor at 100m

At first I though that I got some problem with my shooting, I could see the same the effects shooting the same suppressor with both of my two rifles. I notice that the effect with the 7mmRM was bigger than with the 6.5*55 rifle. That gave me a reason to start try to isolate the problem.

I started to examine the suppressor and after a while looking at the baffles I found the problem. At the same time I also found a easy solution for this problem. This picture below shows the first baffle of a AseUtra NS .30 suppressor that I been using.

First baffle AseUtra NS .30 looks like a crater on the moon.

First baffle AseUtra NS .30 looks like a crater on the moon.

The diameter of a caliber 0.30 bullet is about 7.82mm so this baffle hole should be about 8.6 mm to give the .30 bullet some space to fly thru. The problem was that it measured about 7.7mm! That means that if I would shoot a .30 bullet thru it the bullet would actually touch the baffle and thats a big problem! Both a accuracy and safety problem to address. My conclusion is that this is the problem with my first / second round hitting outside the group problem. Looking at all the baffles you could see the effects of multiple rounds thru the suppressor.

The visible tear and wear on the baffles inside the AseUtra NS

The visible tear and wear on the baffles inside the AseUtra NS

My solution was to open up the hole again. I think that the life of this suppressor soon to be over. So to give the bullet (and my self making the hole) some margin of error I made the hole 9.5mm. This will make the suppressor less effective suppressing the noise but it will also let more heated gases pass thru. That gives some longer time shooting before freeboore boost kicks in. This is the same first baffle after the operation.

All the baffles drilled to 9.5mm on a AseUtra NS .30 suppressor

All the baffles drilled to 9.5mm on a AseUtra NS .30 suppressor

I notice a small increase of noise when shooting 6.5*55 but the noise level felt the same when shooting the 7mm RM. But the best thing about this operation is that my issues with first / second round shift is gone. This is the first 10 rounds thru the suppressor at 100m, it shows 5 rounds 180gr Berger Hybrid (I lost one shot to the left, false recoil management) and 5 rounds 168gr Nosler Accubond Long Range. This CCBS shows that the first round problem is no longer an issue.

7mm 180gr Berger Hybrid and 168gr ABLR at 100m after fix of suppressor

7mm 180gr Berger Hybrid and 168gr ABLR at 100m after fix of suppressor

So the conclusion from this experience is that when the suppressor and muzzle brakes starts to get really used it actually makes the hole thru smaller. This wear and tear is actually something you need to monitor on your suppressor or brake so it don’t become a safety issue or give you a accuracy problem. The second conclusion is that it’s better with a bigger bore suppressor , it gives more margin of accuracy errors and from the freeborn boost.

Good luck shooting!

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