Suppressor topics to analyze

[William Perkins]

I have been thinking and compiling a list of topics that I thought would have appeal to suppressor users. In no particular order here they are.

1. What is the 'bullet flight noise' of various calibers. Particularly .22lr, 9mm, .45 ACP, .223 Rem. , .308 Winchester, and .50 BMG. This test would place the microphone 1 meter from bullet flight at ~100 yards. The shot should be suppressed or at the very least, from inside an insulated building to minimize the gun blast from corupting the data.

2. HOW does a Radio Shack meter compare to a appropriate meter? We KNOW they are NOT adequate. But what are the results? IS IT POSSIBLE that they can be used under NON mil spec circumstances to achieve results that are useful for an amateur ("a person who engages in . . . for the pleasure of it rather thatn the money")? In THEORY it seems that if the meter was placed 20-50 feet from the flight path (over a concrete apron instead of the suggested grassy surface)there MIGHT be enough ground reflection so that it would effectively lengthen the duration of the blast so that it would fall within the performance capabilities (ie. rise-time) of the microphone. We know this data would NOT be comparable to a Larson/Davis system but the intent is to enable AMATEUR a cost effective means to develop OBJECTIVE data.

3. What evidence is there to support ANY of the claims of 'Frequency Shifting' suppressors. Manufacturers have claimed this of their design for years. Is there ANY proof.

4. Dozens of states now have range protection. A stipulation of many of these is complliance with HUD standards. What meter do THEY use?

5. Al Paulson remarked that ATF does not use a meter that complies with Mil-Std. (The rise time of the microphone is too slow) How are the results different from ones that DO meet Mil-Std. How do those compare to the procedure that Robert is using?

6. Suppressors have POI/POA changes when suppressore are installed. The Knights suppressor can be installed in different positions to compensate for this. What is the effect of 'peel washers' in a similar application. For example. A suppressor that shifts POI 4 MOA to the left, is less desirable than a suppressor that shifts POI 4 MOA up/down. How effective is adding peel washers to 're-clock' the suppressor to 'adjust' POI?

7. How do suppressors compare to muzzle breaks in recoil reduction? This should be an OBJECTIVE evaluation. Not a subjective one

I know Robert is going to have his hands full with a project like this one. There is an untapped thirst for this topic that is not quenched with the monthly magazines or gunshow books that are on the market.

[mpallett]

Robert and I have already discussed measuring flight noise, and impact noise.

The main issue is so much to do, so little time.

Keep Quiet,

Matthew

[William Perkins]

I would also find it interesting to test firearms with and without the aftermarket buffer that are available.

The Ruger 10/22 bolt stop pin can be replaced with a Volquartsen or Buffer Technologies pin. I hear a difference when the rifle is shot. I wonder how it would meter.

On an UZI, I have a friend who added a section of "fuel line hose" to the recoil rod and spring. He cut the length down by a 1/4" at a time until he felt that he could hear/feel the bolt bottom out on recoil. Then he cut a new piece 1/4" longer than the one he just removed. I have not shot the gun before/after for comparison but he feels strongly that it makes a noticable difference in feel and sound.

Even the pistols now (1911, Glock, Sig etc) have aftermarket buffers available. Do they meter different with the buffer when they are suppressed?

[silencertalk]

I put such a buffer in my 10/22 and it made a big difference for noise. I am thinking one for my UZI might make sense.

I don't plan to meter it. It works, and is cheap.

[silencertalk]

2. HOW does a Radio Shack meter compare to a appropriate meter? We KNOW they are NOT adequate. But what are the results? IS IT POSSIBLE that they can be used under NON mil spec circumstances to achieve results that are useful for an amateur ("a person who engages in . . . for the pleasure of it rather thatn the money")? In THEORY it seems that if the meter was placed 20-50 feet from the flight path (over a concrete apron instead of the suggested grassy surface)there MIGHT be enough ground reflection so that it would effectively lengthen the duration of the blast so that it would fall within the performance capabilities (ie. rise-time) of the microphone. We know this data would NOT be comparable to a Larson/Davis system but the intent is to enable AMATEUR a cost effective means to develop OBJECTIVE data.

The problem with a Radio Shack or other meter is that the peak-hold feature has a trigger and that part does not respond fast enough. I don't think the results are valid even for casual testing.

My system does not use a trigger as I store all samples before and after the event. I store these as over 24 MILLION voltage levels at 96,000 times per second (the A-duration (main blast) of a gunshot might be about 1/1500 of a second). I can go back to it and find the peak. It cannot be 'missed,' so normal rules do not relate to what I do. My system does not miss the event. Some people think it does, but they are too invested in the old-style meters rather than the new sampling meters which typically cost $30,000 and up.

You can duplicate my system for $700 + a laptop and it does most of what a dedicated $30,000 meter does. It is harder to use correctly than a stand-alone meter though.

[William Perkins]

If you can do all this analysis with only $700 worth of equipment that is impressive. That expense is well within reach of most amateurs.

What I am also looking at as I continue to digest the information that you are displaying is the 'graphs' that you have posted. These DO show which suppressors work best in each frequency. http://www.silencertests.com/images/car15test.jpg This graph shows a curious dip at around 340 Hertz. Is it truly that effective in that region? It seems the efficiency of "frequency shifting" designs can be demonstrated better with a graph than they can be by a poet.
Thanks for the forum. Best of luck.

"When someone throws dirt at you, remember, all they are doing is losing ground."
Ben Franklin

[silencertalk]

I think it is more likely that cans act as a notch filter than literally 'shift' the energy to somewhere else.

[William Perkins]

This is one of the issues I have never understood. When a manufacturer says that their suppressor is a "frequency shift" design I infer that this means that the suppressor takes the energy of the blast wave and "converts" the energy from the perceptable human hearing range into energy that is emitted outside the range of human hearing. It is "shifting" the frequency from the audible spectrum into the inaudible.

I have often suspected that what actually happens is that the design of a suppressor is particularly good at ATTENUATING specific frequencies but it is not "shifting" anything. I am NOT condeming the use of the term "frequency shift" just trying to understand its meaning. Is it just a clever marketing description like the using the term "artificial environment" instead of "wet?" I infer from your post that "notch filter" at 340 Hertz just means the suppressor is particularly GOOD in that frequency but the suppressor does NOT convert that energy into another frequency, or is there another explaination for the dip at 340 Hertz?

Being happy doesn't mean everything's perfect. It just means you've decided to see beyond the imperfections.

[Tugnut]

'Frequency shift' is just a bunch of hocus-pocus, IMO. Just like 'artificial environment', just like you mentioned.

While there is definitely some high science involved in designing cutting-edge suppressors, I do believe that some manufacturers (AWC in the past especially) prey on consumer ignorance.

[Kevin/AAC]

I think that best scenario is to always rely on hearing the silencer first hand, or an independent comparison between many different silencers. It's too bad that a couple a manufacturers have ruined comparison articles in printed periodicals. This has been a huge disservice to consumers. In any other industry consumers would have been outraged. First hand experience and/or independent testing are the only ways make an educated decision.

As a consumer and a manufacturer, I really appreciate silencertests.com. AAC works with many firearm manufacturers, military, and law enforcement agencies to continually evolve and improve every aspect of our products. Sound is only one aspect of making a good silencer. Size, weight, durability, accuracy, and functionality are also very important features. But, after all they are called "silencers."

It would be wonderful if someone could independently test every important aspect of each silencer available. This is just too expensive and time time consuming. The fact is the military tries to do this with each silencer purchase and it takes two years, an unlimited budget, and they still do not always make the best decision. There are just too many varibles in testing or even designing silencers. There is a fair amount of art involved. If this were not the case everyone would be able to make great silencers for every gun in every caliber. KAC, for example has a tremendous budget, they are able to do a lot of R&D and produce many excellent silencers. They also have Doug Olson.

[William Perkins]

1) I copied this from the AWC website.
"A good example of this "deception" is the comparison of sound between a .308 caliber rifle and a 300 WIN MAG rifle. The meter will tell us that both rifles produce the SAME decibel level of noise. Upon firing these rifles, however, we would all agree that the 300 WIN MAG sounds louder! What the decibel meter doesn't tell us is that although both rifles produce the same peak sound pressure level (SPL), the 300 WIN MAG holds its peak duration longer. In other words, remains at full sound value LONGER!"
I have read this many times and I believe it. It would be interesting if Robert figures a way to measure the area under the curve of these two cartridges, and then QUANTIFY the difference. It wouldn't prove anything we don't already know, but I think it would be interesting.

"So easily are we the dupes of our own prejudice."
Percival Lowell

[silencertalk]

The 3D graphs would show this with ease.

[plooker]

I agree that its hocus pocus. A train going by with its air horn going doesn't change its pitch because someone designed it to do that.