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Thread: silencer volume calculations?

  1. #1
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    silencer volume calculations?

    Anybody know if there is a calculation or rule of thumb for how much volume a suppressor needs to be? Would think it would have to do with powder burn rate, powder amount, and pressure.

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    Just for clarification. I understand there are lors of trade offs and variables. Baffle design is a important player, weight, etc.

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    Looking online. Found some dude on reddit that had some info.

    https://www.reddit.com/r/NFA/comment..._calculations/

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    "Bigger is Better, all else being equal". IIRC, assuming a 100% burn the amount of gas, by weight, is about the same as the powder charge.

    Your desired result also factors in. While the math may indicate the "perfect" suppressor contains XXX volume, in the real world size and weight matters more in some cases. If you want "Hollywood Quiet" you need length and volume, but if you want practical size and "good enough" you go shorter and smaller.

    Back in the day Dr Dater came up with his basic design guidelines in a booklet called the "Art of Silence".


    A. Internal volume should be 20 x the internal volume of the bore.

    B. The entrance/blast chamber should be 40% of the free volume of the suppressor.

    C. Length should be 6 - 7 x the diameter.

    Has that changed with his more modern designs? I dunno.

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    Baffle design way more important. My biggest can, bowers vers9s, is also the loudest

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    Excellent information! Exactly what i was looking for! Hadnt heard of Dr. Dater until now. I cant find any of his publishings online. Is their a place where i could find them?
    Baffle design is super important. Just looking for a general starting point to base it off of. In the automotive world their is the saying "theres no replacement for displacement". Obviously putting a 200cfm carb on a 427 motor wouldnt be ideal (think punching freeze plugs in a flashlight tube). But if you slap a 1000cfm carb on our hypothetical 427 (if were dreaming lets dream big, its a 427 cammer) it will kinda wake it up. On the flipside, if you take a 1.0 litre geo metro motor and put a 1000cfm carb on it... lol
    Anyways. Cars aside. Baffle design is super important. But gotta have the " right" amount of space for your baffles to deal with the flow/pressure properly.

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    As far as I know that one booklet is his entire bibliography! Never seen one myself, the quote is from some notes I took while reading some books and articles on suppressors back in the day that referenced his book. Modern baffle designs work more efficiently so things may have changed since the 80s. I think a lot of the time a designer starts with a new design baffle by putting a lot of them in a long tube, measuring the sound reduction, then shortening it a baffle at a time to find the "sweet spot" where one less makes it too loud to be competitive, but one more is not much quieter and it would be longer than the competition so probably wouldn't sell well.

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    Lol! That explains it. Everywhere i had looked people just refer to his writings. I found a email address for his consulting company. I emailed it asking for any information on his publications or where to get them. Havent heard back yet and most likely wont.
    As i am not a ffl/sot i dont have the luxury of being able to do extensive testing on my baffle design. So trying to gather as much data to calculate where the neighborhood of what i am trying to accomplish would be.
    When registering a suppressor is it best to register it as to long? I have heard conflicting things as to whether homebuilt suppressors can be takedowns. Silencer shop sells a stacked takedown solvent trap kit. So would think that its legal to be shorter than specified on the form?

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    "Modular" suppressors that have multiple sections that can be added on or removed at will exist, but IIRC ATF on a Form 1 only allows an inch or two shortening from what you had approved on the other types. Like you screwed up the threads after you serial numbered the tube and had to cut the end off and start over, for example. Starting with 24" and ending up @ 9 is not gonna fly. But a modular design that can still be assembled full length should be OK.

    You might want to start hanging around the silencer-specific forums, along with other Form 1 builders a few industry pros also post and give advice.

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    As always, good feedback. Looking into silencertalk.

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    Heres a calculator for boyels law. Putting it here so it can be found again

    Www.omnicalulator.com/physics/boyels-law

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    Back in the 60s, the US Army conducted an experiment with the M14; they found that a plain metal pipe (no baffles) that was 3' long, 2" dia (IIRC the dimensions) was as effective as the silencers available.
    The point is, you need a device that allows complete powder burn and gas dispersion. This can be done in many ways, including a very long barrel, a long pipe, or a very efficient baffle set in a smaller pipe.

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    That is very interesting. I guess it would make sense. If it was a open ended tube would think that it would direct the actual sound foreward. If it was a enclosed tube (with a hole) could see where that would work.

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    Quote Originally Posted by ericthered View Post
    That is very interesting. I guess it would make sense. If it was a open ended tube would think that it would direct the actual sound foreward. If it was a enclosed tube (with a hole) could see where that would work.
    I think it had an endcap, but it's been at least 20 years, so I can't swear to it

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    Quote Originally Posted by ericthered View Post
    That is very interesting. I guess it would make sense. If it was a open ended tube would think that it would direct the actual sound foreward. If it was a enclosed tube (with a hole) could see where that would work.
    They have been making such devices for some time and they call them linear compensators.
    Youtubers say it moderates sound significantly.

    https://www.newfrontierarmory.com/pr...comp-1-2-x-28/

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    I have seen those linears. Almost bought one a couple of times out of curiosity. Some are pretty cheap. But i got distracted by the whole silencer thing and what, had some crazy idea that i want to try. So now instead of spending $30-100 i am spending a lot more lol!

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    From what i understand a linear just directs the sound forewa3d. So off axis it does sound quieter as it is being directed away from you

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