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Barrel Harmonics Associated With The Target

CharlieNC

Gold $$ Contributor
The attached report is a bit lengthy! Using principles presented by Kolbe, Vaughn, and Long a method was developed to use the target to decifer the barrel harmonic frequency and amplitude based on conducting an Audette ladder to identify a node. While many vibrations occur, the initial results indicate the frequency responsible for this type of charge weight node occur at the speed of sound as proposed by Long, but because this longitudinal wave causes a transverse vibration at the muzzle.

At this early stage the approach is offered as a method to easily characterize the muzzle frequencies and amplitiudes which are exhibited on the target, and in turn to learn how to modify these parameters with loading, etc.

I'm a number cruncher, and look forward to insight from those who have a more extensive knowledge of the mechanics.
 

Attachments

The attached report is a bit lengthy! Using principles presented by Kolbe, Vaughn, and Long a method was developed to use the target to decifer the barrel harmonic frequency and amplitude based on conducting an Audette ladder to identify a node. While many vibrations occur, the initial results indicate the frequency responsible for this type of charge weight node occur at the speed of sound as proposed by Long, but because this longitudinal wave causes a transverse vibration at the muzzle.

At this early stage the approach is offered as a method to easily characterize the muzzle frequencies and amplitiudes which are exhibited on the target, and in turn to learn how to modify these parameters with loading, etc.

I'm a number cruncher, and look forward to insight from those who have a more extensive knowledge of the mechanics.
I read enough to get the gist of the paper, That being speed of angular change and how that relates to positive comp/OBT and other tuning "theories." I can summarize where I've found the flaw to be, through my own vibration analysis testing. They are, and so did I for a long while, assume this is all about frequency. It's not. It's PHASE TIME. Essentially, the frequency is a constant(reasonably true) and we are changing phase time...working with as little as a single wave form and manipulating its position relative to bullet exit. And yes, that has a lot to do with why I constantly scream to move tuners in very small increments. Those sine wave targets that I and others have posted show us how far it is between wave forms, err in tune to completely out of tune, as well as the respective group shapes along that wave form. That's the key and no, it's not a secret or voodoo. It's a methodical test(my tuner test that some call a sine wave test) that lets you see and quantify each adjustment, how many between... and group shapes along a single standing wave. The test is simple. It shows ON THE TARGET, 3 very important things. It shows top and bottom of the bbl swing(sine wave), it shows how many marks between top and bottom, as well as top and middle, which is technically the node, and it shows repeatable group shapes along that standing wave. IOW, it shows you all we need to make a tuner work. It doesn't explain the science to the nth degree but it shows much of it, literally in a picture that you drew with your own rifle...yourself. Our common use of the term node is incorrect in the context of a shooting forum. We talk about being in a node and such but the node is technically where the bbl moves the fastest and shoots worst. Anti-nodes are the top and bottom spike or trough, where the bbl "stops" and changes directions. Positive compensation can only happen at the top, to my understanding on that point, and it stands to reason, even in my little brain.

There are many, many smarter people than I, even on here, but there may not be anyone that has worked harder, done more research and testing, than little old me, on this one narrow subject.

Aside from pc, I believe I have enough understanding of the subject of what's going on with tuners specifically, to explain it in terms that most anyone can understand and SEE for themselves....or I try my best to. I have every customer shoot a test that shows these things. Not me, but them. It's a light bulb kinda moment when you see the things I describe and predict seeing from my test, for yourself and by yourself. It's remarkable how predictable the group shapes are and how little tuner travel is needed. Many top shooters see the same thing when doing seating depth and powder charge development. That's not a coincidence because ultimately, tuners do the same as load work does. That being, optimizing bullet exit with optimal muzzle position. The load changes exit timing but the tuner changes muzzle timing(position)...phase time.

My first experience with tuners on cf rifles was in 2007. I went to a match in 2008 in which I didn't have one, I was pre-loaded and the tune left me.(nats) I don't think I've shot without a tuner since then or very near. I started testing and developing my own tuner in 2014, as soon as the patent on the Browning Boss expired. Actually, that's when I started selling them. I had done a ton of work prior to it, waiting for it to expire.
 
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I read enough to get the gist of the paper, That being speed of angular change and how that relates to positive comp/OBT and other tuning "theories." I can summarize where I've found the flaw to be, through my own vibration analysis testing. They are, and so did I for a long while, assume this is all about frequency. It's not. It's PHASE TIME. Essentially, the frequency is a constant(reasonably true) and we are changing phase time...working with as little as a single wave form and manipulating its position relative to bullet exit. And yes, that has a lot to do with why I constantly scream to move tuners in very small increments. Those sine wave targets that I and others have posted show us how far it is between wave forms, err in tune to completely out of tune, as well as the respective group shapes along that wave form. That's the key and no, it's not a secret or voodoo. It's a methodical test(my tuner test that some call a sine wave test) that lets you see and quantify each adjustment, how many between... and group shapes along a single standing wave. The test is simple. It shows ON THE TARGET, 3 very important things. It shows top and bottom of the bbl swing(sine wave), it shows many marks between top and bottom, as well as top and middle, which is technically the node, and it shows repeatable group shapes along that standing wave. IOW, it shows you all we need to make a tuner work. It doesn't explain the science to the nth degree but it shows much of it, literally in a picture that you drew with your own rifle...yourself. Our common use of the term node is incorrect in the context of a shooting forum. We talk about being in a node and such but the node is technically where the bbl moves the fastest and shoots worst. Anti-nodes are the top and bottom spike or trough, where the bbl "stops" and changes directions. Positive compensation can only happen at the top, to my understanding on that point, and it stands to reason, even in my little brain.

There are many, many smarter people than I, even on here, but there may not be anyone that has worked harder, done more research and testing, than little old me, on this one narrow subject.

Aside from pc, I believe I have enough understanding of the subject of what's going on with tuners specifically, to explain it in terms that most anyone can understand and SEE for themselves....or I try my best to. I have every customer shoot a test that shows these things. Not me, but them. It's a light bulb kinda moment when you see the things I describe and predict seeing from my test, for yourself and by yourself. It's remarkable how predictable the group shapes are and how little tuner travel is needed. Many top shooters see the same thing when doing seating depth and powder charge development. That's not a coincidence because ultimately, tuner do the same as load work does. That being, optimizing bullet exit with optimal muzzle position. The load changes exit timing but the tuner changes muzzle timing(position)...phase time.

My first experience with tuners on cf rifles was in 2007. I went to a match in 2008 in which I didn't have one, I was pre-loaded and the tune left me. I don't think I've shot without a tuner since then or very near. I started testing and developing my own tuner in 2014, as soon as the patent on the Browning Boss expired. Actually, that's when I started selling them. I had done a ton of work prior to it, waiting for it to expire.

I don't know that we had a significant disagreement, in that charge weight provides the phase shift in this case.
 
I don't know that we had a significant disagreement, in that charge weight provides the phase shift in this case.
Maybe not, but the way I read the paper was a common thought process a few years ago and some still chase frequency as the key. I have found that phase time is the key. Glad we agree. I think there's more to be learned if we don't look the wrong way for progress is all.
 
I read the article, the claim that the OBT has vertical dispersion component, whereas the OBT theory emphasis that bullet exit time should be when the muzzle diameter is crossing the zero offset line, has limited theoretical or technical information to support it.
 
I read the article, the claim that the OBT has vertical dispersion component, whereas the OBT theory emphasis that bullet exit time should be when the muzzle diameter is crossing the zero offset line, has limited theoretical or technical information to support it.
That info was literature review, whereas to me it appears the longitudinal speed of sound transmission is correct but that it drives a vertical transve vibration at that rate. At this point my focus is on a method to analyze the target to learn what the freq, amp, etc are associated with load optimization.
 
That info was literature review, whereas to me it appears the longitudinal speed of sound transmission is correct but that it drives a vertical transve vibration at that rate. At this point my focus is on a method to analyze the target to learn what the freq, amp, etc are associated with load optimization.
The vertical component is still there due to the barrel harmonics. BTW, There is a horizontal component too, but not as critical as the vertical one. Thus, both barrel vertical displacement and barrel muzzle dilation at muzzle are happening at the same.

It is evident that recoil force, and more specifically, barrel upset can drastically affect the accuracy equation more than any load optimization.
For example, a 6PPC shot from 20lbs rifle is inherently more accurate than a 300WM shot from 5lbs rifle.

Add to that, barrel profile is most of the time not studied. Example, 1.3" straight barrel vs pencil barrel.
 
The vertical component is still there due to the barrel harmonics. BTW, There is a horizontal component too, but not as critical as the vertical one. Thus, both barrel vertical displacement and barrel muzzle dilation at muzzle are happening at the same.

It is evident that recoil force, and more specifically, barrel upset can drastically affect the accuracy equation more than any load optimization.
For example, a 6PPC shot from 20lbs rifle is inherently more accurate than a 300WM shot from 5lbs rifle.

I'm afraid your missing the key point, that is this a computational method to analyze a target to specifically determine the harmonics that are happening when conducting a charge weight node study. No more just speculating based on various theories, but actual analysis which then the contributing factors can be quantified.
 
I'm afraid your missing the key point, that is this a computational method to analyze a target to specifically determine the harmonics that are happening when conducting a charge weight node study. No more just speculating based on various theories, but actual analysis which then the contributing factors can be quantified.
As computational method vs target analysis:
Since there are many factors/contributors that all happening at the same time. The engineering solution is to model the system, rifle/load/shooter (or rifle supported by rest/mechanical recoiling machine) and then study the contribution of each factor to the outcome (accuracy at the target).

Al Varmint: Studied barrel harmonics using FEA and did POA vs POI analysis
Long: Studied barrel dilation/contraction due to powder explosion vs radial dispersion of the bullet

I also studied the Barrel dilation/contraction "nodes" along the barrel and its influence on MV SD. More specifically, by studying the derivative of the bullet acceleration along its path in the barrel
 
I'm afraid your missing the key point, that is this a computational method to analyze a target to specifically determine the harmonics that are happening when conducting a charge weight node study. No more just speculating based on various theories, but actual analysis which then the contributing factors can be quantified.
The only analysis to be made is what's on the target. Tuners can only tune "some things". I've never seen or heard of any tuner being able to tune out atmospheric conditions such as wind direction/intensiity,air density,etc. These conditions are constantly changing from the time you start 'til you're through say nothing about barrel temp and fouling. Even with tuners,you're still a great disadvantage without wind flags and the ability to use them. The best you can do is read the target....compare it to what the flags are doing and make the necessary adjustments. Shoot sighters when you can.
 
The only analysis to be made is what's on the target. Tuners can only tune "some things". I've never seen or heard of any tuner being able to tune out atmospheric conditions such as wind direction/intensiity,air density,etc. These conditions are constantly changing from the time you start 'til you're through say nothing about barrel temp and fouling. Even with tuners,you're still a great disadvantage without wind flags and the ability to use them. The best you can do is read the target....compare it to what the flags are doing and make the necessary adjustments. Shoot sighters when you can.
I completely agree about wind but do you believe than changing powder charge or seating depth can be used to adjust for other atmospherics, such as temp and density? If you do, then you must also agree that tuners work. Because either way, the end result is timing bullet exit with optimal muzzle position. And yes, the target is the real test.
 
THANKS CHARLIE and commenters! Great article and info and as was stated, this world
we live in is in a constant mode of change and everything in it is constantly changing
to a greater or lesser degree. The key is to dance in harmony with it as best we can.
 
As computational method vs target analysis:
Since there are many factors/contributors that all happening at the same time. The engineering solution is to model the system, rifle/load/shooter (or rifle supported by rest/mechanical recoiling machine) and then study the contribution of each factor to the outcome (accuracy at the target).

Al Varmint: Studied barrel harmonics using FEA and did POA vs POI analysis
Long: Studied barrel dilation/contraction due to powder explosion vs radial dispersion of the bullet

I also studied the Barrel dilation/contraction "nodes" along the barrel and its influence on MV SD. More specifically, by studying the derivative of the bullet acceleration along its path in the barrel

So does it surprise you that all that the bending frequencies modeled by Al and others are not the ones observed on the target, but harmonics of the speed of sound? Long did not study poi, but conjectures regarding group size. Faster bullets hit lower on a target and Kolbe is the only one I've seen that actually instrumented a barrel to correlate with the shot vs just comparing to a calculation, to demonstrate positive compensation. None of this provided a clear characterization of what we observe, which is why I undertook this study a couple of years ago, from a quantitative perspective vs conjecture. At this point I don't propose to have all of the answers, but once again a method to analyze a target to help develop understanding.
 
What is the 'modification' that was applied from Long's theory to the last/third method? Is it just the idea that transverse waves are also created that travel at the speed of sound?

And, the 'fact' that the harmonic slope varies by distance to the target would explain why loads that are accurate at short range are much worse at long range! It doesn't have to do with the bullet 'going to sleep'. For me, very cool.
 
I completely agree about wind but do you believe than changing powder charge or seating depth can be used to adjust for other atmospherics, such as temp and density? If you do, then you must also agree that tuners work. Because either way, the end result is timing bullet exit with optimal muzzle position. And yes, the target is the real test.
i don't know about where you shoot,but at the ranges I've shot at the air density is constantly changing. I keep a temp/humidity guage on my bench always. The air density even changes at different places on the range. Air density is different in the shade than downrange in the sun. Temp swings of 20-25F and humidity changes of 20-30percent in 2 hrs is not uncommon.......would drive me crazy making tuner adj'ts.
I've found using wind flags helps me more than anything.
 

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