Interesting data. The tuned and untuned paths are closer than I expected per the node/antinode idea. I’ll think about it later… I can’t reason why a random oscillation at one end of a loaded cantilever would oscillate the other end the same way every time.
Group convergence with .22LR - yea or nay?
- Thread starter grauhanen
- Start date
Does an "A" tuning fork sound a 440 Hz tone only if you hit it in precisely the right way? Will it vibrate at 380 Hz or 500 Hz if you hit it just so? Or will it always sound a 440 Hz tone whether you hit it gently or a sharply, or if you strike it from 90 degrees or 45 degrees?
Of course it isn't at EXACTLY the same place. If it appears so we only need to measure yet more precisely and we'll prove it ain't. The point is that it repeats nearly enough to be useful,ie. exploited by tuning to achieve less vertical at a selected distance. Remember too that the waves we are working with here are harmonics which by definition are more repeatable and stable. This brings us back to the tuning forks.
There are some things that bias what happens at the start, though. We aren't firing it in space where everything is free to move in any direction without bias. We're firing it on the surface of the earth, in its gravity, with it oriented in a specific way. A bare barrel, i.e. sans tuner, isn't stiff enough to not sag by some amount under its own weight. Adding a tuner in cases where you'd use a tuner adds to that sag. In both cases, that biases how it will move once it starts moving. And it is biased in the same plane with regard to the overall rifle's centre of gravity, too. You don't tend to have a lot of mass hanging off the side of a rifle. What does hang off of it tends to be in the vertical plane. Trigger and stock below, rings and scope above. So that, too, will bias the movement to some degree. Does the barrel to exactly the same thing every single time? Of course not. But its general movement is similar enough from shot to shot that we can consider it a predictable thing. I think it is safe to say that the variance in the ammo is a larger source of variance on target than the movement of the barrel.
Kolbe's barrel movement traces don't show indications of random initial movement direction. Nor do typical shooting results. If it were randomly flipping the up/down orientation of the initial barrel movement that would affect the rest of the movement trace accordingly, and you'd see wild fluctuations in vertical on target as a result. A well-tuned gun that puts round after round through the same ragged hole would be impossible. If bullets are generally leaving the muzzle of a given barrel with a 0.25-0.5 MOA addition to the initial launch angle that would mean in half the cases where it started moving in the opposite direction you'd see it swinging 0.25-0.5 MOA downwards instead. That would mean 0.5-1.0 MOA variance on target due to nothing but the change in launch angle. Add in the effect the muzzle velocity would add to that and you're talking about even more vertical on target. A slow shot leaving at +0.5 MOA launch angle when the barrel is swinging upwards would then be leaving at -0.5 MOA launch angle when the barrel is swinging downwards. So not only is it already going slower, it is now aimed 1 MOA lower than before, so it is going to hit even lower. You'd never see ARA benchrest shooters shooting perfect 2500 scores if that were happening. It would be impossible. No, I think it is safe to say that barrels move in generally the same fashion from shot to shot. Not perfect molecule-for-molecule repeatability, of course. But more or less the same way every time. The ammo's own component variance surely outweighs it by a good deal.
I obviously don't mean molecule-for-molecule. It would be very possible if you time the bullets to leave the barrel when it is flat. The multiple modalities could also cause smaller absolute vibrations at certain times. There are peaks and plateaus on your deflection chart which occur close to when you characterize accuracy gains through positive compensation.
Consistent deflection suggests that peak inaccuracy occurs at the opposite time as I thought— when the barrel is swinging through zero deflection and has its highest velocity.
I’m surprised that the longitudinal wave caused by combustion would convert to transverse deflections that consistently. But I guess there is little basis to build an expectation around that.
Thanks for the explanation and the data, very compelling
Shorty, the question is whether anyone other than you or your acquaintances, someone who is credible, who has some kind of acknowledged .22LR credentials or recognized experience, someone without a vested interest in the problem can be found who supports your view that convergence is a regular "thing" with .22LR.
As a result, referring to your own experience as "proof" is a non-starter.
Besides, as I suggested months ago, your silhouette distance reference is of little value because you didn't prove convergence. A more reliable demonstration of convergence requires showing the same rounds (rather than ammo from the same lot) converging to a smaller group (MOA-wise) further out than closer in. To be sure, this is occasionally seen in testing facility tunnels where the results for the very same rounds can be compared at 50 and 100 meters.
In short, find some outside "expert", online or in print, who supports the idea that convergence with .22LR occurs regularly and purposefully. If you or any reader doesn't find such outside it doesn't prove you are wrong. It may prove, however, that no one who is reliable agrees with you.
I have pointed to Bryan Litz who says convergence isn't a thing except for random occurrences. Of course it's possible that Litz may not be the final word.
Outside of interested readers, is there any recognizable authority on .22LR who agrees with Shorty, someone who explicitly says .22LR convergence is regular? Surely if Shorty is right it can't be difficult to find outside proof.
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Go. Do. The. Test. Yourself. I've done the test or ones similar to it many times before. You are the one that has not yet done so. So I'm speaking from experience, and thus far, you are not. Do I have to make a thread entitled "10-yard increment challenge" and give it 97 rigid rules and plainly state it is just a challenge for yourself and NOT a competition in order to entice you into finally doing the test? Heh.
Shorty, repeating yourself and simply saying something is true doesn't make it so. Challenging me to shoot as you suggest doesn't make it any more correct. To help your case please provide reference to outside sources, either online or in print, that support the idea of regular .22LR convergence.
If as you insist your claim is so obviously correct, reliable ballisticians or reputable sources ought to agree with it. Where are they? Help yourself and direct readers to outside sources that support regular .22LR convergence.
I would really like to see such information and learn more. I would also say in this forum that I was wrong to doubt you.
Of course if reliable sources that support your idea can't be found, the unavoidable conclusion will be that your idea of regular .22LR convergence remains unverified and without merit.
If as you insist your claim is so obviously correct, reliable ballisticians or reputable sources ought to agree with it. Where are they? Help yourself and direct readers to outside sources that support regular .22LR convergence.
I would really like to see such information and learn more. I would also say in this forum that I was wrong to doubt you.
Of course if reliable sources that support your idea can't be found, the unavoidable conclusion will be that your idea of regular .22LR convergence remains unverified and without merit.
Physics is physics. Thanks for admitting physics is too difficult for you to understand.
"I even wrote a program to propagate the trajectories and calculate about where the downrange point of convergence would be." -Bryan Litz
Kind of a strange reply in my eyes, actually. He says he's got an old Enfield that seems to exhibit positive compensation due to an entirely different mechanism, which he thinks is the entire rifle flexing due to recoil. And says he's open to the idea of weights on a barrel influencing positive compensation. But then for some reason says he doesn't think modern rifles could do what the Enfield does because the modern ones are too stiff. Yeah, ok, but I didn't say anything about comparing modern bench guns to old service rifles, either, hehe. Anyway, he says positive compensation is hard to argue against, and now says convergence is not only a thing but he's written a program to estimate where it is happening in the case he was testing. Sorry, Glenn.
"Clayton,
Thanks for the question.
In my published work on tuners so far, I haven’t tested for positive compensation, or ‘convergence’. My tests were all only at 100 yards, which is too close to study convergence for centerfire rifles. My test was only looking at the claims of increased precision at 100 yards that tuners are supposed to produce. I was testing to see if the ‘smallest group setting’ on the tuner was repeatable, and found that it was not. It’s a case where a shooter can follow the instructions, and arrive at a ‘best’ tuner setting, but if the test is repeated, a different ‘best’ setting is found. My intent is to explain how this means the tuner ‘isn’t working’, especially when compared to groups fired from the same rifle before the tuner was installed, and seeing the same precision.
Having said all that, convergence, aka positive compensation is a different thing. The concept of it is hard to argue, and there is historical precedent with the Lee Enfield rifle. I actually purchased an original Mk4 Lee Enfield rifle, along with original ammo (containing cordite), and fired many groups at 300 yards, on a Shot Marker, with radar. Even at 300 yards, I was able to detect a slight bias towards positive compensation with that rifle. Positive compensation being defined as the shots dispersing less in vertical than their MV and BC would suggest. I even wrote a program to propagate the trajectories and calculate about where the downrange point of convergence would be. So I’ve seen and measured positive compensation, but still question if any barrel ‘harmonics’ are involved.
From my perspective of looking at that Lee Enfield rifle… It’s barrel isn’t free floated, it’s captured by the stock by several bands including up to about an inch from the muzzle. What I noticed from shooting that (relatively light weight) rifle a lot with very old ammo (which had incredibly high ES in MV), is that I swear I could tell from the recoil which shots were ‘faster’ and which were ‘slower’, even if it was only the extreme outliers I was detecting. This makes me question; if I can feel the difference in recoil between the fast vs. slow shots, certainly the gun is ‘feeling’ this also as a strain proportional to the variable stress. I picture a scenario in which, upon firing, the recoil ‘bends’ the barreled action slightly in the shape of a rainbow/leaf spring. Higher recoiling (higher MV) shots do this more, and hunch the muzzle into a down-angle more, than lower recoiling (slower) shots. I think this is a reasonable mechanism to explain the positive compensation I see with that rifle, as opposed to a theory of barrel ‘harmonics’, considering it’s a captured barrel.
In summary, I am open to positive compensation as a mechanism that barrel weights could perhaps influence, in general. However, I believe that modern rifles with stiff actions, and floated bull barrels simply don’t have the same mechanism as the Lee Enfield to manifest variations in recoil energy into variations in muzzle pointing, at least not to a magnitude that’s detectable within the rifles’ precision.
Take care,
-Bryan"
I guess some people can change their views when coming across new evidence.
Kind of a strange reply in my eyes, actually. He says he's got an old Enfield that seems to exhibit positive compensation due to an entirely different mechanism, which he thinks is the entire rifle flexing due to recoil. And says he's open to the idea of weights on a barrel influencing positive compensation. But then for some reason says he doesn't think modern rifles could do what the Enfield does because the modern ones are too stiff. Yeah, ok, but I didn't say anything about comparing modern bench guns to old service rifles, either, hehe. Anyway, he says positive compensation is hard to argue against, and now says convergence is not only a thing but he's written a program to estimate where it is happening in the case he was testing. Sorry, Glenn.
"Clayton,
Thanks for the question.
In my published work on tuners so far, I haven’t tested for positive compensation, or ‘convergence’. My tests were all only at 100 yards, which is too close to study convergence for centerfire rifles. My test was only looking at the claims of increased precision at 100 yards that tuners are supposed to produce. I was testing to see if the ‘smallest group setting’ on the tuner was repeatable, and found that it was not. It’s a case where a shooter can follow the instructions, and arrive at a ‘best’ tuner setting, but if the test is repeated, a different ‘best’ setting is found. My intent is to explain how this means the tuner ‘isn’t working’, especially when compared to groups fired from the same rifle before the tuner was installed, and seeing the same precision.
Having said all that, convergence, aka positive compensation is a different thing. The concept of it is hard to argue, and there is historical precedent with the Lee Enfield rifle. I actually purchased an original Mk4 Lee Enfield rifle, along with original ammo (containing cordite), and fired many groups at 300 yards, on a Shot Marker, with radar. Even at 300 yards, I was able to detect a slight bias towards positive compensation with that rifle. Positive compensation being defined as the shots dispersing less in vertical than their MV and BC would suggest. I even wrote a program to propagate the trajectories and calculate about where the downrange point of convergence would be. So I’ve seen and measured positive compensation, but still question if any barrel ‘harmonics’ are involved.
From my perspective of looking at that Lee Enfield rifle… It’s barrel isn’t free floated, it’s captured by the stock by several bands including up to about an inch from the muzzle. What I noticed from shooting that (relatively light weight) rifle a lot with very old ammo (which had incredibly high ES in MV), is that I swear I could tell from the recoil which shots were ‘faster’ and which were ‘slower’, even if it was only the extreme outliers I was detecting. This makes me question; if I can feel the difference in recoil between the fast vs. slow shots, certainly the gun is ‘feeling’ this also as a strain proportional to the variable stress. I picture a scenario in which, upon firing, the recoil ‘bends’ the barreled action slightly in the shape of a rainbow/leaf spring. Higher recoiling (higher MV) shots do this more, and hunch the muzzle into a down-angle more, than lower recoiling (slower) shots. I think this is a reasonable mechanism to explain the positive compensation I see with that rifle, as opposed to a theory of barrel ‘harmonics’, considering it’s a captured barrel.
In summary, I am open to positive compensation as a mechanism that barrel weights could perhaps influence, in general. However, I believe that modern rifles with stiff actions, and floated bull barrels simply don’t have the same mechanism as the Lee Enfield to manifest variations in recoil energy into variations in muzzle pointing, at least not to a magnitude that’s detectable within the rifles’ precision.
Take care,
-Bryan"
I guess some people can change their views when coming across new evidence.
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