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Thread: How a muzzle device works to enhance accuracy

  1. #1

    How a muzzle device works to enhance accuracy

    How a muzzle device works to enhance accuracy


    CYA friends:


    It's been almost 30 years since I spent a hard year of my life testing, and all the finical resources I could gather, to develop the muzzle device we all take for granted today in the world of accuracy.


    The process is well documented in my book, "The ART Of Rimfire Accuracy".



    And after almost 30 years now, a bunch of folks are still confused as to what a muzzle device does, and why.



    The parallel node:



    CYA friends, if any of you folks, who don't already understand, would like to run a simple spearment about barrel vibrations, then I'm going to make the process as simple as humanly possible.


    The first thing you'll need is a length of 3/32" rod, welding rod is perfect.


    And you'll need a bench vise....


    Clamp one end of the 3/32" rod in a bench vise, with exactly 21-1/2" sticking out of the jaws of the vice.


    The other end floats of course.


    This replicated a gun barrel with one end attached to an action, bedded in some sort of stock, with the other end free floating.



    Take a felt tip marker and place a mark exactly 4-3/4" back from the end of the rod.


    This is the location of the parallel node in a 21-1/2" length of 3/32" rod, with one end clamped and the other end floating.


    Here's a couple pictures:






    _____________________________






    The above picture describes how to cause the rod to vibrate so you can get a good visual look at how the parallel node acts.


    The rod will vibrate by other methods, but, this is the best way to keep it stationary so you can see exactly what's going on.



    _______________________________



    CYA friends, over the next few days I'll discuss the parallel node and its length.........


    Plus, the fact that no matter how fast you cause the rod, or barrel, to oscillate, the exact center of the parallel node does not move closer to, nor further away, from the end of the rod.......or the end of a naked gun barrel.



    This is why once you get the exact center of the parallel node to the exit of the crown, by using a properly weighted and positioned MD, ahead of the crown, the exact center of the parallel node remains at the crown forever.....


    In other words, the muzzle is stopped.......literally, physically stopped.


    The length of the parallel node changes, depending on the severity of the barrel oscillations, but, once the muzzle is stopped, the exact center of the parallel node remains at the exit of the crown forever, no matter how severe the barrel oscillations.



    More later.


    Your friend, Bill Calfee


    ________________________


    PS:


    CYA friends, once you master getting the rod to vibrate so you can see what's actually taking place, studying barrel vibrations becomes a fascinating endeavor...



    Please keep something in mind; the parallel node location I've shown you is only for a 21-1/2" long, 3/32" rod.


    A 21-1/2" length of 1/8th diameter rod has a different parallel node location, just as do different sized gun barrels.



    Please keep something else in mind:


    Once you master getting the rod to vibrate so you can see what's happening, you need to remember that the visual vibrations you're seeing are several hundred times greater, by actual measurement, or maybe even a thousand times greater, than that which a rifle barrel actually vibrates.



    For instance:

    When you watch the vibrations die away, and see the length of the parallel node increase, imagine what that increase in length is on a rifle barrel.

    And you'll also see, as the vibrations die away, and the length of the parallel node increases, that the exact center of the parallel node does not change.....


    No matter how fast you cause that rod to vibrate, the exact center of the parallel node remains 4-3/4" from the end of the rod.


    The same thing happens with a rifle barrel.......bc

    Last edited by Bill Calfee; 07-05-2019 at 08:38 PM.

  2. #2

    Understanding how a gun barrel vibrates when fired

    Understanding how a gun barrel vibrates when fired


    CYA friends:


    Before someone can understand what a muzzle device is used for, and how it works, one probably needs an understanding of how a free floating gun barrel vibrates when fired.


    I inserted the words "free floating" in the above sentence...


    But, even if one had fore end pressure on the barrel from the stock, from that point on to the muzzle the same vibration pattern would occur.


    The only difference there would be, is the exact center of the parallel node would be closer to the muzzle, since the barrel from the upward pressure to the muzzle represents a much stiffer barrel, as far as how the barrel would vibrate when fired.

    _____________________________




    ______________________


    When you run this test, and try to hold the barrel at any location other than the parallel node, your thumb and finger will deaden the vibration process.


    ______________



    CYA friends, let's say you simply took your finger and pushed the end of the rod to one side, then released it, not holding the barrel with the other hand at the parallel node.

    The end of the rod would simply swing back and forth until it subsided.


    In this case, all you've done is stress the rod back at the vise, which when let go causes the rod to rebound from the stress, until the alternating stress diminishes completely.


    In a gun barrel when fired, the bullet passes through the entire length of the barrel.



    More.....


    Your friend, BC
    Last edited by Bill Calfee; 07-07-2019 at 05:07 AM.

  3. #3

    If you're interesting in knowing...

    If you're interesting in knowing...


    CYA friends:


    It's almost impossible to run this simple test and not gain a pretty good understanding of how a gun barrel vibrates when fired.






    I took the time to design this simple test, so anyone seriously interested in what a muzzle device is used for, and why it enhances accuracy, could understand why.



    CYA friends, I took the time to do this, because social media has fostered so much goofy nonsense about muzzle devices, and what they're used for, and how they work.



    ____________________



    If you're serious about understanding what a muzzle device is used for, and how it works, you'll take time to run this simple spearment.



    Your friend, BC

  4. #4

    Question

    Hi Bill

    What do you think is the reason that causes the barrel to vibrates in the first place.


    A barrel still vibrates up / down and left / right even when clamped in a sliding bearing such as in a ammo testing tunnel.

    In such a sliding bearing it can only slide backwards dead parallel to the barrel (checked with a dial gauge) this compensates for any sagging of the muzzle.

    Also the center of mass is inline with the bore similar to what I suspect they do in a rail gun.

    The pressure acting on the bullet is concentric and symmetrical so may expand and stretch the barrell.

    Regards
    Graham

  5. #5

    Friend Deveng

    Quote Originally Posted by Deveng View Post
    Hi Bill

    What do you think is the reason that causes the barrel to vibrates in the first place.


    A barrel still vibrates up / down and left / right even when clamped in a sliding bearing such as in a ammo testing tunnel.

    In such a sliding bearing it can only slide backwards dead parallel to the barrel (checked with a dial gauge) this compensates for any sagging of the muzzle.

    Also the center of mass is inline with the bore similar to what I suspect they do in a rail gun.

    The pressure acting on the bullet is concentric and symmetrical so may expand and stretch the barrell.

    Regards
    Graham

    ______________________


    Friend Deveng:


    Have you ran the spearment with the 3/32" rod?


    The reason I'm asking you this; is that by running this simple spearment most all of your questions will be answered.



    Your friend, BC



    ___________________



    PS:


    CYA friends, if any of you folks are serious about wanting to understand barrel vibrations and what a muzzle device is for, and how it actually works, you need to run this simple spearment with the 3/32" rod.


    That way we'll all be on the same page when discussing the various issues surrounding barrel vibrations and the use of a muzzle device.

  6. #6

    Yes and more

    Hi Bill

    Yes I did run your experiment and played a bit more.

    Here is a photo


    Vice mount.JPG



    I am pointing to the felt tip mark 4 3/4" in from the end of the 21 - 1/2" long 3/32 welding rod.

    I could not take the photo and flick the rod at the same time ( it takes 2 hands)

    I tested using the same lengths 3/32" aluminium welding rod

    also 3/32" Silicon Bronze welding rod

    And 1/8" Nickel Bronze welding rod all 21- 1/2" with a 4 3/4" mark

    They all behaved just as Bill said with the node point at the felt tip mark and it makes no difference on the type of welding rod or the diameter.


    I manufacture scientific demonstration equipment

    In my workshop I have a Vibration Generator driven by a Sine wave generator in which I can adjust the frequency and amplitude.

    I attached the 3/32" aluminium welding rod with 21 -1/2" standing up with a mark 4 3/4" from the top.

    I drove this with a frequency of 36Hz which appears to be it's first resonant frequency, on repeating there tends to be about 2 Hz tolerance.

    The image was exactly like how it performed in the vice like Bill described.

    There is 1 standing wave.



    36Hz.JPG




    Since I had the ability I dialed up the frequency until what appears to be the next resonant frequency.

    This was at 97Hz and 2 standing waves appeared with the end node moving to 2 7/8" from the end.



    97Hz.JPG



    I then dialed up the frequency to the next resonant frequency at 202Hz

    There was now 3 standing waves and the end node moved to 1 7/8" from the end


    202Hz.JPG


    I then dialed up to the next resonant frequency of 323Hz and the end node moved to 1 11/32" from the end.

    There was no point in taking a photo as the amplitude at this frequency would not show up in a photo.

    These end nodes could be held with your finger as Bill described.

    I repeated the test using a 3/32" Silicon Bronze welding wire with the same dimensions as the aluminium.

    The resonant frequency was 23hz for 1 standing wave.

    The frequencies for the different secondary frequencies was different to what I would have expected but is what was measured.



    Regards

    Graham

  7. #7

    the next step

    Since we can see this clearly, the next step would be to scale a small "MD" on the end and see how it moves the node. Now that would be an interesting demonstration since you have the equipment to do it.

  8. #8

    Photo for Jerry

    Hi Jerry

    I cut another 4 3/4" of 3/32" aluminium welding rod and with masking tape stuck it to the top, no particular reason for this amount of weight.

    4 3/4" welding rod weighs .04903 oz

    Masking tape weighs .00388 oz

    total weight .05291 oz as weighed



    Jerry Photo.JPG

    You can see where the node is now, it has moved closer to the end.

    Also note that a new node formed down towards the bottom end.

    Another thing after I took this photo I started to dialed down the frequency and when it got to 28HZ it went into resonance so quick that it shook the top off before I could react and dial down the amplitude.

    This leads to the question what happens if the bottom node was not there.

    I then repeated the test in the vice like Bill does but with the extra weight on the end.

    The vice will force it not to have the node at the bottom, it vibrated just fine with the new node closer to the end just like in the photo.

    Regards
    Graham
    Last edited by Deveng; 07-10-2019 at 07:46 AM.

  9. #9

    Friend Deveng

    Quote Originally Posted by Deveng View Post
    Hi Jerry

    I cut another 4 3/4" of 3/32" aluminium welding rod and with masking tape stuck it to the top, no particular reason for this amount of weight.

    4 3/4" welding rod weighs .04903 oz

    Masking tape weighs .00388 oz

    total weight .05291 oz as weighed



    Jerry Photo.JPG

    You can see where the node is now, it has moved closer to the end.

    Also note that a new node formed down towards the bottom end.

    Another thing after I took this photo I started to dialed down the frequency and when it got to 28HZ it went into resonance so quick that it shook the top off before I could react and dial down the amplitude.

    This leads to the question what happens if the bottom node was not there.

    I then repeated the test in the vice like Bill does but with the extra weight on the end.

    The vice will force it not to have the node at the bottom, it vibrated just fine with the new node closer to the end just like in the photo.


    Regards
    Graham

    ______________________



    Friend Deveng:


    You might rue the day you decided to get involved with running these tests.......but, I've got a feeling you're just as cited as the rest of the CYA folks.




    Anyway, there is a node at each end of a barrel.....


    And you've already pretty much found out that the action, or bench vise, cancels out the breech end node.



    ___________________________



    Friend Deveng, if you're willing to keep fooling with adding a MD to the 3/32" rod, to move the exact center of the parallel node to the end of the rod, whatever you add needs to be added in a ridged fashion.



    To add more to the mix:


    We're in a conundrum here....


    All of this needs to be done with the rod in a horizontal orientation......since a gun barrel is in that orientation when shot from the bench, or the shoulder.


    So the effect of gravity comes into play.


    But.....................


    That would be most difficult to do using a 3/32" rod.....barrel.



    Trying to move the exact center of the parallel node to the end of the rod, with it in a vertical orientation, may still be very beneficial, though.



    Thank you.


    Your friend, BC

  10. #10

    A bit of fun

    Hi Bill

    PedroS had the same idea to put a MD and see what happens.

    You need to look at the photo with a bit of imagination, I adjusted the weight by adding and removing some Blue Tack Plasticine from the top.

    This moved the node to the end of the welding rod.

    Also every time I added some weight the resonant frequency decreased and finally it reduced to 21Hz.

    This would mean that putting a MD on a barrel it would also slow down the rate of the vibrations and in this instance it slowed them down 41.6%.

    21Hz off.JPG


    21Hz on.JPG

    Regards
    Graham

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