How To Calculate Your Harmonics

[CharlieNC]

With extra time available this Winter I decided to try to better understand harmonics and load optimization. OBT seems to work sometimes for me, and the barrel harmonic calculators are also interesting. In the attachment I have attempted to provide an easy means for anyone to quantify the harmonics of their shooting system using a "given" load (bullet and powder combo). This demonstrates positive compensation, not the top or bottom of the "barrel whip", explains nodes. And nodes at one distance will not necessarily give nice nodes at other significantly distances. Primarily a means to quantify the degree of compensation may be useful to further understand barrel designs, load development, etc. I do not expouse that this is 100% accurate, but introduce it as a tool for refinement to help us understand. Feedback and improved interpretation is appreciated.

 

[Nobody]

And nodes at one distance will not necessarily give nice nodes at other significantly distances.

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Of all the meanings I can derive from that sentence I don't agree with any of them...

Nodes as in groups? Bryan Litz pretty much proved that precision never increases with range, but is pretty much uniform. If it shoots .5 at 100 it will shoot 1.5 at 300 and 3 at 600. The whole idea of a bullet "settling in" is a myth.

Velocity? Again, based on BC almost all bullets of the same design will decelerate and fall according to the laws of fluid dynamics and the muzzle velocity uniformly at range.

I'm not saying I understand barrel harmonics beyond a definition and a general working understanding (no maths). I don't, but I do understand the result of tuning the ammunition to the rifle. My personal experience tracks directly with the results of the experiments and tests in any of Bryan's four books. I am categorically convinced that Applied Ballistics and WEZ Analysis is uniformly correct in describing balistics, and any deviation from that (on paper) is the result of the unique barrel harmonics of the rifle. I have never found it to be anything but uniform at any supersonic range.

 

[CharlieNC]

Nobody, I'm afraid you missed the definition of node in the writeup; its not group size but is sensitivity of vertical POI to charge weight, etc as determined by OCW, ladder tests, etc. And the intent is to further address the "unique barrel harmonics" you mentioned, nothing to do with ballistics per se.

 

[Nobody]

Sorry, I confess my ignorance beyond practical application. Then "node" is velocity node, which is what I thought.

However, "Another significant debate on the method and application is whether the results achieved at one distance, say 100 yards, can be applied accurately at a much greater distance, like 1000 yards.", this does appear to be this idea that a bullet in flight will "settle in" or "even out", or any number of phrases. If you are on a velocity node as measured at the barrel, and small fluctuations in the powder charge are not impacting velocity (Low SD) the bullets are going to slow down and fall uniformly as soon as they leave the barrel. That delta is going to remain constant all other external forces being equal. Barrel harmonics are going to place that impact in some uniform variation of precision, and this is going to give you your group, which is also going to remain constant as you get further and further from the barrel (assuming no wind). To me that "debate" has been settled on the ballistics side. The theory that bullets change velocity and "settle in" is a myth. They decelerate the same, and the precision of the grouping remains constant.

What I'm not understanding is how distance has any bearing on a velocity or a constant group. Certainly vertical dispersion is the most important factor at range (WEZ hypothesizes this mathematically, and 1000s of rounds prove it), but the scientific testing I've seen, and my own results say there is no difference at any range as long as the projectile remains super sonic. Both velocity and grouping stay uniform, which is why ballistic solvers work so well when you input the correct data.

"Accuracy and Precision for Long Range Shooting: A Practical Guide to Successful Long Range Shooting" goes into this in-depth, not from a barrel harmonics perspective (other than to acknowledge it's there), but from a practical ballistic perspective (what the rifle actually does). I don't really know a darn thing about how barrel harmonics work, other than watching the BR guys who run barrel tuners, and recording my own shooting (loading for groups rather than velocity), but these things are all very well fleshed out now on the practical side. I would think that any theories about barrel harmonics (or scientific testing) ought to work backwards from the ballistic side, which is a lot easier to gather and graph data than to try and figure what's going on in the millisecond the primer goes off. We know it's there, and we know how the charge effects it at both short and long range. I have found that most of the time I'm getting best groups on a flat node. Not saying it's always like that, but in the last two comp guns the best groups at 100yds have also been the flattest loads with the lowest SD/ES.

 

[Ledd Slinger]

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If it shoots .5 at 100 it will shoot 1.5 at 300 and 3 at 600. The whole idea of a bullet "settling in" is a myth.

No it is not myth. Shoot enough loads and bullets through barrels of different grooves, bores, twists, rifling types, makes, etc. and you will find the error in that statement

 

[IdahoSharpshooter]

How would one go about calibrating his/her harmonica in the first place?

OOPS...!! I misread this one.

 

[Nobody]

No it is not myth. Shoot enough loads and bullets through barrels of different grooves, bores, twists, rifling types, makes, etc. and you will find the error in that statement

Well, you can cleve to the theory, but Litz has done some exhaustive testing using multiple targets at multiple ranges along the bullet’s flight path, and they track exactly like Newtonian physics would suggest. He never found an instance where a diverging bullet did anything but keep diverging, or a bullet behaved differently than it’s BC would suggest outside of individual barrel harmonics. I’d argue environmentals over sleeping bullet theory if you suddenly get tighter groups at a further range, and my guess is if you kept shooting and used a reasonable sample of a 20 or 30 shot group you’de find that wasn’t the case.

While it’s rare my dope matches my solver perfectly, I don’t find that a diverging group at 100 yds suddenly comes back together @ 600. I don’t find my vertical dispersion fluctuating at range any more than the models suggest it would at a given SD for that load. Doppler radar is what generated the G7 and G8 drag models. That’s measuring velocity from the barrel all the way to the target, which is why these models are so accurate. If the same bullet didn’t behave the same way no solver would work. They don’t have an algorithm for a bullet that “goes to sleep”.

You can say it’s just my opinion, but there are people measuring and testing these theories with the right tools. It’s not backyard shooting, but full bore with a control group and fancy instruments. It’s not a 3 or a 5 shot group, but a 50 or a 100 shot group. The WEZ produces the the vertical POI changes based on velocity, the barrel harmonics/whip certainly effect it, but it effects it uniformly at all ranges with a specific load, based on how tight a group a rifle will shoot with that load.

I’m not making any of this up, and I don’t consider it opinion. Read the books, because they’re exhaustive and explain all the methodology, as well as the math that goes into the predictions as compared to actual shooting data. If I get anything wrong it’s because it isn’t open in front of me.

Barrel harmonics still has quite a bit of theory to it. I think the last bits of theory in ballistics are disappearing mainly because we can now see, track, and measure each shot at every point along its flight path from muzzle to target.

 

[Ledd Slinger]

Your statement said accuracy remains the "same" all the way out. Not necessarily saying it gets "better" at distance. I'm saying your quote that it remains the "same" is in error. I've seen some extremely accurate groups at 100 completely go to shit at yardages as close as 300.

 

[ireload2]

You make the same old mistake of assuming that for proportionally smaller groups at longer range the path of the bullets must begin to converge. That is not true. All that has to happen is the paths diverge more slowly. That is consistent with the bullet going to sleep and the reduction of nutation.
You point towards the work of others as if you have no first hand knowledge of the subject. I have a rifle that behaves in this manner and has since 1972. I can assure you it is no myth.

Well, you can cleve to the theory, but Litz has done some exhaustive testing using multiple targets at multiple ranges along the bullet’s flight path, and they track exactly like Newtonian physics would suggest. He never found an instance where a diverging bullet did anything but keep diverging, or a bullet behaved differently than it’s BC would suggest outside of individual barrel harmonics. I’d argue environmentals over sleeping bullet theory if you suddenly get tighter groups at a further range, and my guess is if you kept shooting and used a reasonable sample of a 20 or 30 shot group you’de find that wasn’t the case.

While it’s rare my dope matches my solver perfectly, I don’t find that a diverging group at 100 yds suddenly comes back together @ 600. I don’t find my vertical dispersion fluctuating at range any more than the models suggest it would at a given SD for that load. Doppler radar is what generated the G7 and G8 drag models. That’s measuring velocity from the barrel all the way to the target, which is why these models are so accurate. If the same bullet didn’t behave the same way no solver would work. They don’t have an algorithm for a bullet that “goes to sleep”.

You can say it’s just my opinion, but there are people measuring and testing these theories with the right tools. It’s not backyard shooting, but full bore with a control group and fancy instruments. It’s not a 3 or a 5 shot group, but a 50 or a 100 shot group. The WEZ produces the the vertical POI changes based on velocity, the barrel harmonics/whip certainly effect it, but it effects it uniformly at all ranges with a specific load, based on how tight a group a rifle will shoot with that load.

I’m not making any of this up, and I don’t consider it opinion. Read the books, because they’re exhaustive and explain all the methodology, as well as the math that goes into the predictions as compared to actual shooting data. If I get anything wrong it’s because it isn’t open in front of me.

Barrel harmonics still has quite a bit of theory to it. I think the last bits of theory in ballistics are disappearing mainly because we can now see, track, and measure each shot at every point along its flight path from muzzle to target.

 

[Alexander-M]

Admitting some ignorance in this subject, I have a simple question:

Why, given a round barrel and round bullet, all discussions of nodes, tuning, whip, etc., always consider motion of the barrel only in the vertical plane? Wouldn't the barrel have any horizontal motion as well; or for that matter, actually whip or move in a circular path? What if the rifle were 'clamped' sideways?

Thx!

Alex

 

[ireload2]

The actual motion will be affected by the receiver shape and its resistance to flex in various axes. The rear locking Lee Enfield rifles are said to have compensation at one range due to unusual harmonics caused by the asymmetrical receiver sections.

Admitting some ignorance in this subject, I have a simple question:

Why, given a round barrel and round bullet, all discussions of nodes, tuning, whip, etc., always consider motion of the barrel only in the vertical plane? Wouldn't the barrel have any horizontal motion as well; or for that matter, actually whip or move in a circular path? What if the rifle were 'clamped' sideways?

Thx!

Alex

 

[Alex Wheeler]

I respect Litz because he actually tests things. But, he does not discount positive compensation. He does not tune that way, and until your shooting pretty small it does not become obvious. I will pretty much agree with Litz, that if you work up a .5 moa load at 100 yds it will most likely grow in a linear fashion relative to distance. But theres plenty of 1kyd ladder/chrony data out there showing vertical much smaller than would be possible given the ES in the group. Most of the time those loads that are shooting .1s vert at 1k will be .2s or .3s at 100, sometimes worse. But since most of the guys that are shooting at that level are more interested in winning matches and breaking records than they are at trying to prove things to others that will not take their word for it, we'll likely never see a real "report" or scientific data sheet to "prove" it. It would be a waste of time because most would not believe the data anyhow. We have talked about doing it many times, but always end up saying "why"? Maybe after I retire.

 

[dkhunt14]

I respect Litz because he actually tests things. But, he does not discount positive compensation. He does not tune that way, and until your shooting pretty small it does not become obvious. I will pretty much agree with Litz, that if you work up a .5 moa load at 100 yds it will most likely grow in a linear fashion relative to distance. But theres plenty of 1kyd ladder/chrony data out there showing vertical much smaller than would be possible given the ES in the group. Most of the time those loads that are shooting .1s vert at 1k will be .2s or .3s at 100, sometimes worse. But since most of the guys that are shooting at that level are more interested in winning matches and breaking records than they are at trying to prove things to others that will not take their word for it, we'll likely never see a real "report" or scientific data sheet to "prove" it. It would be a waste of time because most would not believe the data anyhow. We have talked about doing it many times, but always end up saying "why"? Maybe after I retire.

I agree with this. The one thing Litz didn't account for is once you shoot through paper at 100, you just affected the airflow to the bullet. I don't care how thin the paper is, you changed it. The bullet needs that airflow to stay stable. Watch videos of air flowing over bullets and you will see the wake is even out in front of the bullet and continues behind.

Nobody says it shoots smaller, but after it settles it isn't affected as much. It just doesn't drift as far out with the conditions, like some others above had said. Matt

 

[holstil]

Admitting some ignorance in this subject, I have a simple question:

Why, given a round barrel and round bullet, all discussions of nodes, tuning, whip, etc., always consider motion of the barrel only in the vertical plane? Wouldn't the barrel have any horizontal motion as well; or for that matter, actually whip or move in a circular path? What if the rifle were 'clamped' sideways?

Thx!

Alex

Same here, don't claim to be an expert. I believe when I see my groups change stringing directions that may be what is happening. Often while tuning I see vertical stringing then diagonal clumping then horizontal stringing. To me, a horizontal group is the same as a vertical group, out of tune. Waterline means little to me in this regard, it's either a small group or it needs more tuning.

Not sure if this relates. I have a frequency machine for golf shafts. One end is clamped and the other end drawn back and let go. Watching the shaft as it moves makes me think a barrel may have similar characteristics. This is done with seamless shafts. Of course there is no bullet screaming down the shaft with pressure and rifling. But still gets my gears turning.

 

[steve123]

I respect Litz because he actually tests things. But, he does not discount positive compensation. He does not tune that way, and until your shooting pretty small it does not become obvious. I will pretty much agree with Litz, that if you work up a .5 moa load at 100 yds it will most likely grow in a linear fashion relative to distance. But theres plenty of 1kyd ladder/chrony data out there showing vertical much smaller than would be possible given the ES in the group. Most of the time those loads that are shooting .1s vert at 1k will be .2s or .3s at 100, sometimes worse. But since most of the guys that are shooting at that level are more interested in winning matches and breaking records than they are at trying to prove things to others that will not take their word for it, we'll likely never see a real "report" or scientific data sheet to "prove" it. It would be a waste of time because most would not believe the data anyhow. We have talked about doing it many times, but always end up saying "why"? Maybe after I retire.

Actuality, sometimes it's hard to believe unless one has experienced what really happens over and over vs conforming to the "what must be true" because that supposed truth has to be true even though it's not 100% true.

There's reasons things happen the way they do whether we understand those reasons or not, as you say the evidence is on the paper.

I've seen it and can't make sense of it, we can make use of it though.

 

[Alex Wheeler]

Totally separate from positive compensation is bullet stability, which can be effected with the tune all by itself. You can see it in how the bullet holes cut the paper, and it will effect wind drift. Thats why you hear guys talk about a good load shooting through conditions.

 

[Nobody]

Litz doesn't do opinion. He takes an opinion, a theory, or a hypothesis and tests it. He details exactly how he constructed the test, shows you all the data, and then forms a conclusion. Nothing up his sleeve. Since it's his algorithms in many or most solvers, and he sells WEZ software, it's pretty easy to test his conclusions yourself by shooting and seeing how the results stack up. I'm not really arguing. I'm just pointing to actual evidence, and it happens to conform to my own shooting experience. I intend to take one of his classes if it ever becomes convenient. He isn't JUST a mathematician either. He's more than just a decent marksman.

I guess you have nothing left to learn because you have so much experience. You think I'm a millennial or something? No gray in my beard? I'm nobody. I don't get into competitions to see can claim whose is bigger on the internet. I have plenty of experience. Some of it actually practical in my youth.

 

[Ledd Slinger]

I'm not really arguing. I'm just pointing to actual evidence, and it happens to conform to my own shooting experience. I intend to take one of his classes if it ever becomes convenient.

I guess you have nothing left to learn because you have so much experience. You think I'm a millennial or something? No gray in my beard? I'm nobody. I don't get into competitions to see can claim whose is bigger on the internet. I have plenty of experience. Some of it actually practical in my youth.

I see you just recently joined. Welcome.

Everyone respects Brian Litz. He helped change the game with long range shooting and bullet development. However, you are not on "Sniper's Hide" anymore

This site hosts some of the most decorated and accomplished benchrest competitive shooters in the world. Brian Litz is an excellent source for information no doubt, but not everything he says is 100% accurate. Some things just can't be equated precisely with constants plugged into an equation. Be nice if they could all the time, but they can't. There's so many different barrel characteristics and bullet makes, there's no way he could have tested them all to the point where his words can be written in stone and regarded as gospel. Just because the members on here haven't written a book on it, doesn't mean they haven't ran the same tests as Brian Litz many times. With the level of precision they require for their sport, they've probably even tested all of the same theories to a further extent than Litz ever has.

Basically what I'm trying to say is...The guys you are talking to on this thread are not just "pulling opinions out of there arse". They have actually fired thousands upon thousands of rounds down range at distances up to 1,000 yards and beyond to prove their statements.

 

[CharlieNC]

Totally separate from positive compensation is bullet stability, which can be effected with the tune all by itself. You can see it in how the bullet holes cut the paper, and it will effect wind drift. Thats why you hear guys talk about a good load shooting through conditions.

Alex I have endeveored to provide a clear demonstration of positive compensation, vs the often debated assertion that a node is at the top or bottom of the cycle. As a shooter and gunsmith, do you see any value in the method I have proposed to quantify the harmonic of a barrel? I was hopeful such a quantification could be used to ultimately better understand barrel design and load development. Having worked in r& d for years with the axiom "if you can't measure it, its tough to fix it."

 

[dmoran]

@CharlieNC
This is the most impressive assessment application I've seen in a long time. Very interesting to say the least.
Already gather the same data for my own data assessments, and looking forward to extrapolating it to your model concepts as well, for further assessment value.
Very much appreciate your work and time spent. Thank You for sharing !.!.!
Donovan