Finding the barrel vibration sweet spot

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mdeland
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Re: Finding the barrel vibration sweet spot

Post by mdeland »

Thanks Wayne, I'll keep an eye peeled for a stethoscope and post my finding when I get one, as well. Great thread and most interesting!
BFD
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Re: Finding the barrel vibration sweet spot

Post by BFD »

If you guys are so interested in the nodes and vibrations of rifle barrels, you really should investigate the science of it. This is very well traveled ground.

for instance
https://www.youtube.com/watch?v=KZ7intMz2Y4
TexasMac
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Re: Finding the barrel vibration sweet spot

Post by TexasMac »

BFD wrote: Sun Apr 12, 2020 7:11 pm If you guys are so interested in the nodes and vibrations of rifle barrels, you really should investigate the science of it. This is very well traveled ground. For instance https://www.youtube.com/watch?v=KZ7intMz2Y4
Hi Brent,

Good basic video on nodes and antinodes. What I had forgotten in the first part of my article is a rifle barrel is not an example of a closed boundary system which is the example I used. But regardless my goal was to discuss the possible ways the average shooter can to determine the sweet spot.

BTW, after posting a link to the article on another form I exchanged emails on the subject with a person that I believe you know, namely Richard Christensen (aka Chris).

Wayne
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BFD
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Re: Finding the barrel vibration sweet spot

Post by BFD »

Wayne, if you clamp it in a vice, it is closed on one end. If you don't think that you can "close" by gripping the rifle, then you shouldn't use a vice in the first place, but in the end, you have missed the point of the video. Different methods should NEVER produced different results for the position of the node. That is a property of the material being tested, not the testing materials. Your methods are suspect. Furthermore, you can simply measure back from the muzzle to know where the node is.

Last, if your gun jumps in the sticks, it's not where you are resting it. It is your position and your rifle's stock configuration.

I would imagine, Chris told you about the math.
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Re: Finding the barrel vibration sweet spot

Post by TexasMac »

BFD wrote: Mon Apr 13, 2020 12:40 pm Wayne, if you clamp it in a vice, it is closed on one end. If you don't think that you can "close" by gripping the rifle, then you shouldn't use a vice in the first place, but in the end, you have missed the point of the video. Different methods should NEVER produced different results for the position of the node. That is a property of the material being tested, not the testing materials. Your methods are suspect. Furthermore, you can simply measure back from the muzzle to know where the node is.
Last, if your gun jumps in the sticks, it's not where you are resting it. It is your position and your rifle's stock configuration.
I would imagine, Chris told you about the math.
Brent,

When I said, "What I had forgotten in the first part of my article is a rifle barrel is not an example of a closed boundary system which is the example I used", what I meant to say was a closed at one end boundary system.

So are you saying that the node positions should not change when clamping the receiver vs. clamping the stock. Based on some of my testing (stethoscope method for example) I would tend to agree with you. I expect that the receiver is the location of the closed end regardless if it's clamped there or at the stock. But how about if I use a uniform metal tube and change the clamping location. I would expect the closed end changes with changes in the clamping location. Is that an incorrect assumption?

BTW, with the rifle with a uniform round barrel, measuring back from the muzzle 1/4 of the length of the barrel worked and absolutely agreed with the other testing techniques. But using this approach definitely did not work with the two rifles with 1/2 octagon 1/2 round barrel configurations. Are you implying that it should work as well with these?

Finally, under actual shooting conditions I can move the position of the barrel on the sticks and, using the exact same positioning and hold, the rifle will start to jump as the resting point is moved off the node position. I've tried this several times and use it to fine tune the ideal resting location.

Wayne
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Jimhp02
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Re: Finding the barrel vibration sweet spot

Post by Jimhp02 »

Kurt
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Re: Finding the barrel vibration sweet spot

Post by Kurt »

BFD wrote: Sun Apr 12, 2020 7:11 pm If you guys are so interested in the nodes and vibrations of rifle barrels, you really should investigate the science of it. This is very well traveled ground.

for instance
https://www.youtube.com/watch?v=KZ7intMz2Y4
Brent that looks more like me finding the standing wave of my Ham Radio Antennas :D
You professors make things so difficult :D
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TexasMac
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Re: Finding the barrel vibration sweet spot

Post by TexasMac »

Jimhp02 wrote: Tue Apr 28, 2020 7:02 am I like this
https://youtu.be/HFFJAGeYj1A
Excellent video. I'll have to incorporate it into my article. I don't recognize the presenter.

Wayne
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BFD
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Re: Finding the barrel vibration sweet spot

Post by BFD »

Kurt wrote: Tue Apr 28, 2020 8:46 am
BFD wrote: Sun Apr 12, 2020 7:11 pm If you guys are so interested in the nodes and vibrations of rifle barrels, you really should investigate the science of it. This is very well traveled ground.

for instance
https://www.youtube.com/watch?v=KZ7intMz2Y4
Brent that looks more like me finding the standing wave of my Ham Radio Antennas :D
You professors make things so difficult :D
No, we make things much easier. If you understand the principles, then you don't have to memorize or test and re-invent every new instance of a given phenomenon. I doubt there are many things in BPCR more over-thought than barrel vibration. Nor more things underthought than load testing procedures.
gunlaker
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Re: Finding the barrel vibration sweet spot

Post by gunlaker »

BFD wrote: Tue Apr 28, 2020 9:03 am No, we make things much easier. If you understand the principles, then you don't have to memorize or test and re-invent every new instance of a given phenomenon. I doubt there are many things in BPCR more over-thought than barrel vibration. Nor more things underthought than load testing procedures.
I'd agree with that :-). The math behind this has been taught to first year physics and mechanical engineering students for a long time. Once you understand the basic idea it's pretty easy to get an intuition for many diverse configurations.

I also agree with the idea that stock shape, shooter position, and cross stick height is far more important than resting the node on the cross sticks, although I pay attention to all of them when possible.

As an aside, I once saw a slow-mo video of a .308 being fired and the amplitude of the vibration at the muzzle was far greater than I expected.

Chris.
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Re: Finding the barrel vibration sweet spot

Post by SFogler »

Post by Jimhp02 » Tue Apr 28, 2020 7:02 am
I like this

https://youtu.be/HFFJAGeYj1A
Top
I am glad you posted this video - I saw it before but couldn't find it again. I tested my rifles like this and my Shiloh 30" octagon 45-70 sang like a tuning fork until at the "node" it thumped then started singing again past it. Very obvious, I could hear it audibly not just feel it. I will try to get a stethoscope and see if I can verify my results on my rifles.
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Don McDowell
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Re: Finding the barrel vibration sweet spot

Post by Don McDowell »

I'm still not convinced banging on the barrel of a rifle with a hammer, stethoscope, tuning fork, all while wearing tin foil hats, etc. can replicate the null spot the way a bullet traveling down the barrel driven by several thousand psi can be the same.
AKA Donny Ray Rockslinger :?
mdeland
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Re: Finding the barrel vibration sweet spot

Post by mdeland »

The guy in the video backed up his premise with actual live fire group testing which makes it pretty convincing to my way of thinking. The live fire group testing at each inch back toward the forearm and the harmonics both converged at the same place he had previously marked on the barrel bottom.
Nuclearcricket
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Re: Finding the barrel vibration sweet spot

Post by Nuclearcricket »

A few years back I had #3 1/2 GM barrel put on a rolling block action. In some aspects it wasn't a good choice as I didn't want to get it over weight but that taper barrel made the rifle well under the limit. Total weight came in at about 10 1/2 pounds. In a 44-77, you could say the recoil is slightly zippy. But any way that barrel was the easiest barrel to find the null point on. If you grab the barrel at the end of the forearm and slap the receiver as you slowly let the barrel slip through your hand you can very easily feel the vibrations and also feel when they stop. This method works well with this particular barrel. The same method with my Heavy Shiloh not so well. Maybe I need to hit it with a soft hammer or something other than my hand as you don't feel any vibration when hand slapping the receiver.
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Re: Finding the barrel vibration sweet spot

Post by Dgunner »

Does anyone know if Shiloh offers sweet spot locating and marking on new rifles?
:?:
D-Gunner
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