Barrel Harmonics 101
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Thread: Barrel Harmonics 101

  1. #1
    Join Date
    Jan 2008
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    Exclamation Barrel Harmonics 101

    Barrel Harmonics 101
    By Festus

    Barrel harmonics happen in that fraction of a second when the bullet traverses the barrel. No rifle barrel is ever perfectly straight and even though we are talking about variances that are too minute for all but NASA smart engineers to measure, they are there. As the bullet breaks the crimp on the end of the case, it also may not hit the throat of the barrel perfectly square, again not enough for us to measure but none the less it happens. All of this mechanical yawing and swaging of the bullet into the lands and grooves causes a very fast and very strong vibration for the few milliseconds the barrel is traveled. Each weight and speed of bullet causes a slightly different wavelength of vibration. This is barrel harmonics. If you are a bench rest shooter then it behooves you to tune your barrel to those harmonic vibrations to cancel the sine cosine of the vibration wave to shrink your group by dampening the microscopic barrel movements. Many achieve that with a specialized muzzle brake. Others use a barrel tuning weight attached to the outside of the barrel to disturb the vibration and dampen it.

    I have shot class F target rifles now for over 10 years. I am not a wealthy man so here is what worked for me. I measured the diameter of my barrel and went down to the local auto parts store. I picked up a small hose clamp and proceeded as follows.

    I placed the hose clamp on the barrel 1/4 inch from the end of the muzzle and tightened it down. I fired a three shot group from a rest. I pulled the target and moved the clamp about 1/4 inch and repeated the procedure until I had mapped the barrel's "sweet spot" for a given weight of bullet and a given velocity load. I recorded the distance to the nearest 1/100th of an inch in my dope book.

    I painted the clamp flat black and reinstalled it. I then verified my installation with a three shot group.

    The clamp is just enough mass to dampen the barrels vibration when properly placed and tightened down.

    If it looks dumb but it works, it ain't dumb.

    At the end of the day my rifle shoots a .304 center to center three shot group at 100 yards. It is ugly but it works for me.
    FESTUS
    IN OMNIA PARATUS

  2.   
  3. Thank you for the tips

  4. #3
    Brief reveiw of trigonometry.
    By G50AE
    The trigonometric functions sine and cosine are not spelled with a letter "g".

  5. #4
    Join Date
    Jan 2008
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    Florida Panhandle
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    Talking Thanks for the spelling tip

    I am a gun guy not an English major
    FESTUS
    IN OMNIA PARATUS

  6. #5
    Join Date
    Feb 2009
    Location
    Keysville Va.
    Posts
    304
    Thank's
    Need was the Mother of invention

    It seems that your system is about the same as the BOSS SYSTEM on my Browning .270
    Bill

  7. #6
    You can achieve the same thing by tweaking your reloads to get the best group. It is much more work, but it is consitent and you don't have funny things hanging on you rifle. Each rifle has it's own load that it "likes"

  8. #7
    Join Date
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    Off of I-80 between Des Moines and Cheyenne
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    I've read a paper or two regarding rifle barrel "harmonics" and various ways to dampen them. Looks like you found a method that works for you!

    For what it's worth, a number of us would be put to shame by a lot of the investigational skills and experiences that some here on this forum have. You are one of those guys who see something to investigate and do so. You work on it and come up with solutions that work. Something as intricate and unobservable (directly) as barrel harmonics corrected with something as simple as a hose clamp. Whod'a thunk? Well done.
    1)"When injustice becomes law, resistance becomes duty." -Thomas Jefferson.
    2)"Imagine how gun control might be stomped if GOA or SAF had the (compromising) NRA's 4 million members!" -Me. http://jpfo.org/filegen-n-z/nraletter.htm

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