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Testing muzzle brakes / rifles for relative noise
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Picture of papaschmud
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After perusing the latest discussions around here on the subject of muzzle brakes, I thought I had better to head to the range and do some scientific testing. I personally have two rifles with Vias brakes and while the manufacturer claims virtually no increase in noise, I wanted to see for myself. Noting some of the discussion in the previous thread, I decided to test (with a decible meter) the various rifles both from the shooters position and also from a position 7' behind and 3' to the right of my shoulder. The idea with the second placement was to appoximate the noise level for a guide observing his client's shooting.

I started with the baseline of a Kimber 84 .308 22" barrel shooting 150gr. handloads. The shooter's number was 115 while the guide got nicked at 113. Next up I tested a custom M70 30/06 with a 25.5" tube and a Vias brake firing factory winchester 180gr silvertips. The shooter's number was 115.4 and guide's number was 113. Getting to the meat of the matter, the next test was run with another custom 70. This time a 26" .300 win mag was tested with and without it's Vias brake shooting 190gr. handloads. The with brake numbers showed 116.5 at the shooter and 115.4 for the guide. Without the brake, the shooter got rung to the tune of 115 and the guide got 113.4. The final test was run with an 8" Freedom Arms .454 Casull firing Winchester's 250 grain factory load. The shooter got lit up for 116.2 and the guide got 112.4.

The evidence shows that although some brakes are indeed very loud, the Vias does meet the makers claim of negligable noise increase. The factors most involved in noise seem to be gas velocity and more importantly, barrel length.


Gabe

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Posts: 410 | Location: Granite City, WI | Registered: 10 March 2003Reply With Quote
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Correct me if wrong.
The decibel scale is logaritmic,witch means that every time you increes the noiselevel by 3 db you dubbel the noice.

If i ame corect, the brake incresed the noice by 50-70% depending of the position
 
Posts: 571 | Registered: 16 June 2005Reply With Quote
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Not completely correct jorgen... It requires about a 3db increase for the human ear to be able to notice the increased volume....

Excellent test papaschmud... At least there are some hard numbers involved here... Simply depends on which direction the gas is vented as to where the noise goes....

Ken....


"The trouble with our liberal friends is not that they are ignorant, but that they know so much that isn't so. " - Ronald Reagan
 
Posts: 5386 | Location: Phoenix Arizona | Registered: 16 May 2006Reply With Quote
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quote:
Originally posted by jørgen:
Correct me if wrong.
The decibel scale is logaritmic,witch means that every time you increes the noiselevel by 3 db you dubbel the noice.

If i ame corect, the brake incresed the noice by 50-70% depending of the position


You are correct when you mention that the scale is logarithmic. My understanding is that an increase of one decibel is an increase of 100% of the intensity of the sound. Intensity and perceived volumn are clearly not the same.

The numbers are only useful in that they are comparative and non-subjective. No one would call a 22" barreled .308 a boomer but some folks might shudder in aprehension at the prospect of hunting with an '06 wearing a brake.

I realize all brakes aren't equal, but the Vias has proven in non-subjective data that their brake performs as advertised.

One more note about decibel measurement: I tried testing the meter by subjecting it to loud noise and then slightly varying the volumn of that noise. At over 100 decibles, the difference between say 107 and 110 was very slight. It was perceivable, but only that, not a marked difference. To learn more about decibel measurement and sound perception click the link below.
sound tutorial


Gabe

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Posts: 410 | Location: Granite City, WI | Registered: 10 March 2003Reply With Quote
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Why weren't the first two rifles tested both with and without brake?
 
Posts: 11664 | Location: Henly, TX, USA | Registered: 04 April 2001Reply With Quote
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The .308 doesn't have one.

When I measured the '06 with the brake on and discovered it was no louder than the .308, I thought it pointless to test without the break as it was already rather mild.


Gabe

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Posts: 410 | Location: Granite City, WI | Registered: 10 March 2003Reply With Quote
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This is great, I've been hoping someone would do it with a meter. I wish you had more rifles to test.

I'm still trying to understand how much louder a few decibels is. I need to read your physics lesson again.

What was your perception of the recoil reduction? I called Vias once and they said the recoil reduction was greater at high velocities.


.............................................
 
Posts: 431 | Location: Atlanta, GA | Registered: 29 January 2006Reply With Quote
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I could test all sorts of rifles. Based on the numbers so far, I don't think that most of the "normal" stuff would vary that much.

I bedded and did load developement on an A-bolt (with the BOSS) in 7 rem mag that I'd like to get back here and check both ways. Another neat one to test would be the Competitor .243 specialty pistol I worked on some years back. This pistol had a conventional brake which vented at a 90 degree angle from the bore. Brutal. The noise was overpowering. I took the brake off for the load work.

As far as recoil, the '06 is a cupcake. The brake doesn't hurt, but this rifle wouldn't be hard to shoot either way as the barreled action is a m70 and the barrel is long. It also wears a Pacific Research (now Borden) stock whose dimensions help. As it is, you can't quite watch the bullets hit through the scope, but if I need to shoot from a weird position, I know the scope won't hit me.

The .300 has a noticable increase in recoil without the brake. It's not that hard to shoot bare but with the brake you can shoot it all afternoon.


Gabe

Pa to three sons
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Posts: 410 | Location: Granite City, WI | Registered: 10 March 2003Reply With Quote
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Here is the deal on decibels:

Decibels are a unit of power (like watts or horsepower), not perceived loudness. Acoustic power is related to perceived loudness, so using decibels has a double usefulness - it tells you how much acoustic (or other power) is involved, and it allows the knowledgeable to make useful perceived loudness comparisons. However, that relationship is not linear.

Decibels are logarithmic. So 20 decibels is not twice as powerful as 10 decibels, it is 10 times as powerful.

The typical human can perceive an acoustic power difference of 3 db. 3 db is approximately TWICE as much power as the original reference. A 10 db increase in acoustic power is perceived as twice as loud. But it is actually 10 times as much power.

So, in the .300 Win Mag example, the shooter had an increase of 1.5 db, which would not be perceived as louder, but actually represents 1.21 times as much acoustic power. The guide got 2 db more acoustic power, which is 1.58 times as much power. (Please note that the log calculations are done using "bels" which are 10 decibels, so if the difference is 1.5 decibels, the log used is .15.)

So, as far as PERCEIVED loudness goes, the Vais brake's claims of no difference are justified. As far as actual power hitting your ears, the claims are not justified.
 
Posts: 2 | Location: tmwlaw@gmail.com | Registered: 19 October 2016Reply With Quote
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Excuse me. the 1.21 times should be 1.41 times. (typo)
 
Posts: 2 | Location: tmwlaw@gmail.com | Registered: 19 October 2016Reply With Quote
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I don't know what the books say, but I certainly can perceive a 1 decibel difference when they adjust my hearing aid.


Larry

"Peace is that brief glorious moment in history, when everybody stands around reloading" -- Thomas Jefferson
 
Posts: 3685 | Location: Kansas USA | Registered: 04 February 2002Reply With Quote
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Try it with the "guide" three feet directly off to the side of the muzzle !!

This year I had a hunter with a 300 WM with one of those massive, 4 inches wide, Panzer style brakes. Those are so abusively noisy and you can feel it in your sinus'


Anyone who claims the 30-06 is ineffective has either not tried one, or is unwittingly commenting on their own marksmanship
Phil Shoemaker www.grizzlyskinsofalaska.com
 
Posts: 3126 | Location: Bristol Bay | Registered: 24 April 2004Reply With Quote
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Welcome to the forum. Is there any particular reason you dug up a 10 year old thread for your first post?

As long as we're being technical, dB is not a unit of power. It's just a ratio of two things expressed as a log. It's like saying percent, or a fraction. So you could buy something on sale at -3dB for example (i.e. 50% off). With sound, it's a ratio of the quietest thing that can be heard by an average human to whatever you're measuring (in terms of pressure).

https://en.wikipedia.org/wiki/Decibel
 
Posts: 527 | Registered: 13 November 2008Reply With Quote
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Hey Phil, I had the same experience this year with a 30-06 that had no brake and a hunter void of judgment, and filled with excitement! these damn rifles are loud as hell with or without a brake, if one of ya is in the wrong spot!

I can only suggest that a guide should keep reminding himself that the Red Gods of Hunting gave him fingers to stick in his ears, However in my case its about 50 years too late, Ive reached the point where noise no longer bothers me, I can hardly hear it.


Ray Atkinson
Atkinson Hunting Adventures
10 Ward Lane,
Filer, Idaho, 83328
208-731-4120

rayatkinsonhunting@gmail.com
 
Posts: 30524 | Location: Twin Falls, Idaho | Registered: 04 June 2000Reply With Quote
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