What should a tuner be expected to do?

[Williwaw]

It's good to see you responding here on CGN. Your experience and insight is helpful, especially to readers who may not peruse many other rimfire forums and discussions.

In any case, if they are not wrong about set and forget, it may be testimony to the relationship between tuners and good ammo. While many lots of good ammo often have overlap in ES ranges, if PC explains tuner function, tuners may well work just the same no matter the ES range. They just need good ammo to do what they can.

Thanks for the welcome. I was a little reluctant to wade into a tuner thread on my second post. I well remember the help you were when I started out with my 64MPR.

When I think of PC and the effectiveness of a tune it seems to me that most often(shooting Cx and SK) the ES is greater than what the tune can adjust for. As you know I shoot forty rounds into 8 bulls and then score for both F Class and ARA Unlimited(for chuckles) using OnTarget. I always generate one set of statistics excluding the dropped points. Occassionally that is a wind call fubar but most of them are high or low. These are most likely the rounds that would dictate my ES. Usually this subset is 37 or more rounds, very rarely 35 or 36. By this method I can compare the composite groups height and width. Most often they are close and when they have excess vertical the MV variation attributable is far less than would be expected if I chronoed.Admittedly this is a bit of data editing(read massage) but I have gained confidence in my ability to find a near optimum tune for most lots I shoot.

Some days it feels like the stars have aligned and sometimes I left wondering what the heck is up. But I have had a few very convincing instances where my tuner was not set as I meant it to be. Either it got bumped or was not reset after shooting other ammo. In every instance I was up checking the setting after three or four bulls. Of course this sort of sensitivity is much more likely for someone who shoots every day and only shoots case lots of SK and Lapua.

 

[Leuchtkafer]

You demonstrate as good an appreciation of tuner function as has appeared recently on the Rimfire forum.

There is a debate among rimfire shooters as to how the rimfire tuner does its job. Among the earliest explanations to gain traction and popularity are two that still seem to dominate the discussion. One is that tuners work by achieving positive compensation by means of timing bullet exit from a muzzle that is moving. In brief, slower bullets exit on a higher upward muzzle movement than faster ones. If correct, this explanation requires tuner adjustment for changes in distance to target.

Another early explanation was that a good tuner setting caused the node to be at the muzzle so that it was not moving, "stopped" as it were.

Unfortunately, there seems to be no agreement. What's clear, however, is that it can't be both at the same time.

Experienced and very serious rimfire BR shooters still differ on whether different lots of ammo or different conditions such as temperature require tuner adjustment. I suspect the balance would tilt in favour of the "set and forget" position, that once correctly tuned it works for all good ammo. After all, they would say, it's the barrel that is being tuned, not the ammo.

In any case, it's worth noting that it was curious that the explanation offered above in posts #48 and #51 were based on the ostensible absence of evidence that a tuner was working, which is to say the target was supposed to show when a tuner wasn't doing its job.

Without knowing more details, it remains possible that the target didn't show that the tuner was or wasn't doing its job simply because the ammo didn't do its job. In other words, if the ammo isn't consistent it can be very hard to know what, if anything, a tuner might be doing.

Unfortunately the hard drive on my old laptop died a couple years ago, either certain documents were unrecoverable or I never made a digital copy of them, so I have nothing I can share that clearly demonstrates how and why I chose a particular setting on a certain rifle. I recall an experiment adding the maximum weights to the Harrells that produced horrible vertical stringing (around 3/4" at 50 yards), sadly I cannot locate that example either. The phenomena of the POI jumping up and down is repeatable, I do have an example of that on a second rifle with a Harrells that I had lightened by a couple ounces. My note says "lite tuner" so I believe that to be the case, versus having added the lightest weight attachment, though I am not 100% certain. The POI is fairly stable for most of the target, with a gradual trend of lower impact as the tuner is extended out in it's range, until the high 500's where the jumping phenomena shows up. I used SK Flatnose for the testing, so take that for what it's worth.

https://i.postimg.cc/Vk1CZhK1/lite-tuner.jpg
https://i.postimg.cc/5N8z3Jqn/lite-tuner-B.jpg

Yes, it is certainly difficult to decisively make a determination as to when the tuner is at it's ideal setting. What conclusions can be drawn from this testing set? Not much, honestly. Perhaps the tuner is still too heavy for this particular barrel, I have no idea how it would respond with the tuner being lighter still, though I highly doubt there are any benefits to be had from being heavier given what happened at the end of the range. Would you trust shooting this in the high 500 range, or would you select a different range for more extensive and finer graduation testing?

I've certainly seen the assertions that PC is the way it works, though I have not seen any compelling evidence supported by chronograph data. If anyone is aware of such, I'd be interested in reviewing it. I can't discount it as a possibility, however logically thinking it appears to be an extraordinarily difficult condition to induce in the barrel, reliably and repeatably. As I've described trying to tune bullet exit for that "dwell point" in either peak high or peak low vertical muzzle movement, deviant rounds tend to print vertically away from the main grouping, rather than being drawn into the group. I'm sure you've witnessed faster rounds print inexplicably lower than the group and perhaps slower rounds hit higher as well.

I sit in the "stopped muzzle" camp, and over here there's nothing that can be done about vertical dispersion due to velocity variation, it is what it is. I've tested out to 200 yards over a chronograph with vertical results congruent with what ballistic calculations would predict, so the tuner was mitigating muzzle movement from adding to the vertical successfully. If you can't magically make the vertical better than what would be expected for the velocity spread at 200 yards, being able to do so at a closer distance appears to be more of a fantasy that some have convinced themselves of being a reality.

 

[Williwaw]

I too have a Harrell with a weight set and spent a couple years uncertain as to how or when different weights were indicated. I have finally settled on a method ... at least for now.
This method not only indicates an appropriate weight and an appropriate setting range likely to result in a reasonable tune. Note I do not say optimum because I never do enough testing and comparison to be able to back that up.

The method is to shoot five or 10 shot groups(bigger is better) on a full range of settings,ie. 0,25,50,75,... 500. I scan and digitize the groups(OnTarget) and plot setting vs mean radius. The preffered curve/weight is one that has broad sweeping variations. An inappropriate weight results in a spikey erratic curve. By this method I settle on a weight for that barrel and I select a range to sweep by 2 click steps that is in the middle of a broad stable zone of low mean radii(not necessarily the lowest). Generally this sweep is 50 clicks wide, 5 rounds per setting. On another day I reshoot seven or eight of these and their adjacent settings. On another day I'll shoot ten shot groups of three of these, pick the best one, zero scope and shoot 40 for score. Sometimes I end up trying the second best one but most often I don't.

Obviously there is not much to be gained in winning the stopped vs pc debate because there are so many successful practitioners on either side. In fact, as I understand the two, they both depend on a common concept of muzzle oscillation and differ only in their choice as how to exploit the phenomena. I can't rigorously defend a specific number attributable to PC but whatever it is I'll take it. I also once enjoyed the realization that one of my early tunes was displaying characteristics of negative compensation. All of my work is done at 50 yards. Obviously there is likely a limit to how much barrel flexure and therefore compensatory launch angle range that is possible. Given the extreme drop of the humble 22 I readily accept Kolbe's opinion that anything like full PC is limited to something less than 100 yards.

Great discussion, so helpful hearing other peoples ideas.

 

[Leuchtkafer]

I too have a Harrell with a weight set and spent a couple years uncertain as to how or when different weights were indicated. I have finally settled on a method ... at least for now.
This method not only indicates an appropriate weight and an appropriate setting range likely to result in a reasonable tune. Note I do not say optimum because I never do enough testing and comparison to be able to back that up.

I'd wager most people would prefer to be shooting versus testing What constitutes a sufficient amount of testing, anyway? Many of us are limited in the time and financial resources that we can dedicate towards a test procedure, I ended up playing around with things while just shooting my preferred targets.

Obviously there is not much to be gained in winning the stopped vs pc debate because there are so many successful practitioners on either side. In fact, as I understand the two, they both depend on a common concept of muzzle oscillation and differ only in their choice as how to exploit the phenomena. I can't rigorously defend a specific number attributable to PC but whatever it is I'll take it. I also once enjoyed the realization that one of my early tunes was displaying characteristics of negative compensation. All of my work is done at 50 yards. Obviously there is likely a limit to how much barrel flexure and therefore compensatory launch angle range that is possible. Given the extreme drop of the humble 22 I readily accept Kolbe's opinion that anything like full PC is limited to something less than 100 yards.

Great discussion, so helpful hearing other peoples ideas.

I think you hit the nail on the head there, it's not a debate of "either or" on how a tuner works, but which method one prefers. There are pro's and con's to each approach. I liked the "stopped muzzle" approach for it's relative simplicity, find the range where muzzle movement is mitigated to the maximum possible, then the rest is on the quality of barrel, ammo, and shooter's ability to make the best of it. The downside is there is no potential to benefit from any positive compensation, one is at the mercy of the ammo consistency. Upon further reflection I do see potential to setup a positive compensation condition in the barrel, though I still assess it as difficult and sensitive. Success here depends on the amplitude of muzzle movement, and the speed of it's movement relative to the barrel time of the bullet. Without some sophisticated measuring equipment, one is trying to achieve this flying blind. Just some idle thoughts, could a thinner, more flexible barrel be more suited to this approach versus the 0.850"+ barrels benchrest shooters tend to use? Can enough muzzle movement be induced to realize an improvement at longer distances (100-200y)? This might necessitate a super heavy tuner (relatively, take a Harrells and double or triple the weight) in conjunction with the thinner barrel. Could be some fun experiments for someone with the means to do so. I'm interested in making an adapter to fit one of my Harrells to one of my sporter rifles to play around with, time to get a lathe

 

[grauhanen]

I'd wager most people would prefer to be shooting versus testing What constitutes a sufficient amount of testing, anyway? Many of us are limited in the time and financial resources that we can dedicate towards a test procedure, I ended up playing around with things while just shooting my preferred targets.

I hope Williwaw offers a response, however different it could be from mine. His perspective is welcome.

Preferences aside, what constitutes a sufficient amount of testing is a good question. I'm not a math guy or a statistician, but there are numbers that would present a reasonable level of confidence that results are valid at least a significant percentage of the time. Unfortunately, those numbers are likely to exceed what many shooters, casual and potentially serious, would like to think or are prepared to shoot.

Except by fluke or random accident, successful tuner testing to achieve the best setting is not the product of shooting a few groups at different settings and picking the setting associated with the smallest sized group. Too often new tuner enthusiasts will put a tuner on a rifle, shoot groups at different settings and after matching the smallest grooup with a certain setting declare his work done and the setting determined. It's happened on this forum and continues to do so on many others.

One of the challenges of finding the best tuner setting for a rifle is that there will usually be several settings that offer improved results. That is to say, over the range of a tuner's possible settings, more than one will produce improvement. It's important to note, however, that only one of them will be best. That best setting is often if not always one which should produce improvement over a good number of good lots of ammo. Determining which tuner setting is truly the best from among several that show improvement requires more testing.

Another challenge in finding the best tuner setting is that most shooters will be testing outdoors. Here wind conditions can play a role that interferes with the collection of reliable data. Additionally, shooters will not be using fixtures or vises to eliminate as much as possible shooter inconsistency so there's that potential problem with which to contend.

As a result, successful tuner testing is rarely the product of a day at the range. In 2018 a well respected BR shooter and amateur ballistician who has his own ballistics testing tunnel wrote the following about the ease of tuning a rimfire: "A word of caution. I've never found it as easy to tune a RF rifle as most would suggest it is. Fact is, I've yet to test a rifle in my ballistic tunnel that was truly tuned even when someone brings a rifle and is convinced it's tuned."
See post #41 here h t t p s://www.rimfirecentral.com/threads/50-at-200.1129343/page-3#post-11089975

I think you hit the nail on the head there, it's not a debate of "either or" on how a tuner works, but which method one prefers. There are pro's and con's to each approach. I liked the "stopped muzzle" approach for it's relative simplicity, find the range where muzzle movement is mitigated to the maximum possible, then the rest is on the quality of barrel, ammo, and shooter's ability to make the best of it. The downside is there is no potential to benefit from any positive compensation, one is at the mercy of the ammo consistency. Upon further reflection I do see potential to setup a positive compensation condition in the barrel, though I still assess it as difficult and sensitive. Success here depends on the amplitude of muzzle movement, and the speed of it's movement relative to the barrel time of the bullet.

I understand your comment was made with regard to what Williwaw wrote. I may misunderstand, but to clarify, are you saying that both explanations of how tuners work -- positive compensation and the "stopped muzzle" theory -- are valid and that shooters have only to prefer or choose one or the other?

Does either possible explanation require a different approach to finding the best tuner setting?

 

[Leuchtkafer]

I understand your comment was made with regard to what Williwaw wrote. I may misunderstand, but to clarify, are you saying that both explanations of how tuners work -- positive compensation and the "stopped muzzle" theory -- are valid and that shooters have only to prefer or choose one or the other?

Does either possible explanation require a different approach to finding the best tuner setting?

Yes that's what I see, both approaches are valid and capable of reducing the vertical spread one might otherwise observe if shooting without any sort of muzzle device. I thought of it as trying to find the dwell point at peak maximum or minimum of the muzzles vertical movement cycle before I heard the term "positive compensation". My initial adventure into tuning was using what we'll just refer to as Positive Compensation for the sake of simplicity in communication. I also made the observation you refer to above that there are several setting ranges one will come across during testing that show improvement. Sometimes it was just two clicks that could bring it in, and another two clicks to throw it out. Over a period of months, I didn't feel confident with this level of sensitivity, not to mention a change in ammo usually called for refining the setting again.

I spent some time digging through Bill Calfee's forum and liked his approach. I think I even found where Bill stated what the approximate setting should be for a Harrells on a 0.850"x24" barrel. Bill tends to be rather coy about the juicy details of things, I've gleaned that his approach is more technical in that there is a method to determining how much weight is needed at what distance in front of the muzzle to achieve the "stop" effect, and this holds true barrel to barrel of the same dimensions. He seems to leave it to the reader to experiment and connect the dots of his hints for themselves. I suppose shooting over a chronograph for testing and observing results congruent with the measured velocity spread would be confirmatory of "stopping" the muzzle, and at 50 yards not observing any out of place notably high or low shots that are not congruent with the chronograph. Being able to move off the setting 5, 10, 15, 20 clicks in either direction and not being able to tell a difference in the results is also a good indicator of being at the correct setting, as well as being able to change ammo and not see results that would compel you to adjust the tuner.

 

[Williwaw]

Tuner testing vs shooting ... when is it enough

This is an interesting one for me because for a while I have been avoiding cracking open a new case and testing. At one point this spring I had 5 or 6 half cases that I had tunes for already. I have been comparing my scores from last fall and winter to what I could get this summer with the same ammo. Also to see if the tunes seemed to hold. All this to say I get that testing is not why most of us shoot. Thinking about this I realized I could offer another answer to the original question Grauhanen posed. My practical answer is that a tuner will most often save me 2 to 4 points when I am shooting Cx or a good lot of SK. This is where my imperative to tune comes from ... higher scores.

I also get that it is near impossible and quite impractical to generate a dataset that will withstand true scientific scrutiny. I'm not even trying to ... I'm the only guy I have to convince.

 

[Williwaw]

One of the challenges of finding the best tuner setting for a rifle is that there will usually be several settings that offer improved results. That is to say, over the range of a tuner's possible settings, more than one will produce improvement. It's important to note, however, that only one of them will be best. That best setting is often if not always one which should produce improvement over a good number of good lots of ammo. Determining which tuner setting is truly the best from among several that show improvement requires more testing.

Another challenge in finding the best tuner setting is that most shooters will be testing outdoors. Here wind conditions can play a role that interferes with the collection of reliable data. Additionally, shooters will not be using fixtures or vises to eliminate as much as possible shooter inconsistency so there's that potential problem with which to contend.

IMO there may be dozens of settings that offer improvement over bare barrel. I can think of no reason why only one of them would be best, or maybe better to say I couldn't tell the top half dozen apart on any particular day. For that matter what is the criteria for best. To expand upon this a bit ... we refer to harmonics, think standing waves. Any body remember having seen an oscilloscope in grade 12 physics? That waveform can be walked back and forth by adjusting the tuner position. Slide up and down one wave and it repeats on the next. But the waves are not just smooth idealized sine waves because our systems are flawed and some of the energy has also gone into spurious, non repeating noise. Some positions will prove more robust than others. I'm just looking for something that repeats that improves my score.

I put no faith in fixtures for use in tuning. When it goes bang there is a discrete amount of energy released and I don't get wholly restraining recoil and tuning to that condition and then going home and letting the rifle recoil in any manner which in turn absorbs energy that previously found other expression/outlet.

 

[Williwaw]

In 2018 a well respected BR shooter and amateur ballistician who has his own ballistics testing tunnel wrote the following about the ease of tuning a rimfire: "A word of caution. I've never found it as easy to tune a RF rifle as most would suggest it is. Fact is, I've yet to test a rifle in my ballistic tunnel that was truly tuned even when someone brings a rifle and is convinced it's tuned."
See post #41 here h t t p s://www.rimfirecentral.com/threads/50-at-200.1129343/page-3#post-11089975

I respect this gentlemans opinions in these matters as few others. That said, I would wager that when he says truly tuned his standards for a tune are higher than what I have been able to accomplish ... I just want better scores than I am able to get without. His statement does not dim my enthusiasm for tuners because I also have no knowledge of the shooters who visited his range and their tuner methods/theories/beliefs.

Excuse the chopped up posts, I'm trying to run up my count so the powers that be will give me the keys to the Equipment Exchange.LOL. I hope everyone gets out to shoot this weekend.

 

[grauhanen]

Yes that's what I see, both approaches are valid and capable of reducing the vertical spread one might otherwise observe if shooting without any sort of muzzle device.

Without taking a position on the PC vs stopped barrel debate, it appears that both can't occur at the same time.

One explanation seems to require movement at the muzzle with the timing of the bullet's exit depending on the relationship between the MV of the bullet and the position of the muzzle in it's wave movement. This relationship is established by having the tuner at the best setting. When the muzzle is at the highest point in the wave -- that is to say, when the "launch angle" (if that term is appropriate) is highest -- is when the slowest bullets will exit. Faster bullets will exit with a lower launch angle.

The other, Calfee's "stopped muzzle" requires no muzzle movement, that the node of the wave, where there's the least or no movement, must be at the muzzle, the very exit point of the bullet.

For readers unfamiliar with Bill Calfee, he's a sometimes controversial but well known rimfire benchrest rifle builder (who says he invented the tuner or, as he calls them, "muzzle device"). His elaboration of the "stopped muzzle" theory can be found here http://www.ozfclass.com/articles/1/psm_2005_03.html Readers should be aware that Calfee's ideas about tuners have been disputed, often vigorously, by many including the ballistician Geoffrey Kolbe. See, for example, http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

As noted in previous posts, if a tuner works at different distances with the same setting, then positive compensation seems less likely an answer. The problem is that confirming tuner settings at longer distances is much more difficult than it is for 50 yards, where it can be challenging enough. In any case, finding the best tuner setting can be a trial many shooters are not prepared to undertake.

Fortunately for shooters, understanding the way in which tuners work won't change anything about what they may do.

 

[grauhanen]

IMO there may be dozens of settings that offer improvement over bare barrel. I can think of no reason why only one of them would be best, or maybe better to say I couldn't tell the top half dozen apart on any particular day. For that matter what is the criteria for best. To expand upon this a bit ... we refer to harmonics, think standing waves. Any body remember having seen an oscilloscope in grade 12 physics? That waveform can be walked back and forth by adjusting the tuner position. Slide up and down one wave and it repeats on the next. But the waves are not just smooth idealized sine waves because our systems are flawed and some of the energy has also gone into spurious, non repeating noise. Some positions will prove more robust than others. I'm just looking for something that repeats that improves my score.

I put no faith in fixtures for use in tuning. When it goes bang there is a discrete amount of energy released and I don't get wholly restraining recoil and tuning to that condition and then going home and letting the rifle recoil in any manner which in turn absorbs energy that previously found other expression/outlet.

It's not clear how fixtures or vises may influence tuner results. Perhaps it would have been better not to refer to them at all and simply say that shooter inconsistency or error remains a possible influence that can muddy the results or render them inconclusive. Put another way, it can be difficult to know how much or when the shooter plays a role in producing results that may not be reliable.

Although ignorance isn't evidence, I not aware of any evidence that dozens of tuner settings that improve results can occur with the same barrel and tuner and ammo. If there were literally dozens of tuner settings that were equally sound, finding a tuner setting would be relatively quick and easy. Without causing controversy, many serious RFBR shooters will say that there will be more than one, but that there is one setting that produces the best results. The criteria for that is simple as it shows in achieving higher scores.

 

[Williwaw]

Although ignorance isn't evidence, I not aware of any evidence that dozens of tuner settings that improve results can occur with the same barrel and tuner and ammo. If there were literally dozens of tuner settings that were equally sound, finding a tuner setting would be relatively quick and easy. Without causing controversy, many serious RFBR shooters will say that there will be more than one, but that there is one setting that produces the best results. The criteria for that is simple as it shows in achieving higher scores.

As you would likely guess I don't have any evidence either ... in any of this I will only have my reasons which have shaped a working hypothesis which I have found to have sufficient utility to allow me to use tuners to improve my scores.

I have my reasons for speculating about there being multiple tuner positions that improve performance. One comes from Mike Ezell who manufactures his own tuner for sale. I wish not to provoke or engage in any controversy if I in any way have misunderstood or misrepresent Mike's work. But as I understand it he suggests that there may be a good position in every revolution which I believe is .025 inches with his product(as with Holeshot and Harrell). Another reason is that in my own work I often stop shooting a case after half a case. Occassionally, if a lot doesn't quite achieve the results I'm after I will start over and find a new setting when I go to shoot up the last half. I've done this three or four times and always found a second setting as good as the first, only once possibly better.

Again, not wanting to raise any controversy I'll bring up Purdy and Hopewell. I won't say much about either method but only that after some study and experimentation neither has influenced my methods yet both have many steadfast converts. How can that be so? I suggest because where ever the hell you've cranked your tuner out to there is a setting that will improve matters within half a twist from where you ended up.

Given the above it must be pretty easy to find a tune and only a little harder to find a real good tune one would think. Well its a bit of work for me. My equipment is definitely one step below top drawer, my ammo two down and I shoot outdoors. And the operator is a dubious piece of work too.

 

[grauhanen]

Given the above it must be pretty easy to find a tune and only a little harder to find a real good tune one would think. Well its a bit of work for me. My equipment is definitely one step below top drawer, my ammo two down and I shoot outdoors. And the operator is a dubious piece of work too.

Based on my own experience, I couldn't say how easy it is to find a good tuner setting because I've never found it unchallenging. Since 2017 with my first tuner, then a Lowey, I have tried with various levels of intensity without significant success. Various factors militated against me, not the least of which was an inconsistent approach with insufficient rigour in methods and a misapprehension of what tuners could actually achieve, but also less-than-consistent ammo, not to mention rifles with barrels that weren't especially responsive to the various tuners I've tried.

My current renewed interest is fueled by a new rifle with shorter, slightly slimmer barrel than the heavy-barreled models I otherwise shoot, together with the most solid front rest I've seen. The ammo question always remains. How good is sufficiently good enough for tuner use is a question that for me remains unclear. As you no doubt well know, it can be so difficult to obtain really consistent ammo, the kind which doesn't have a surprise or two (or more) in every box.

 

[emerson]

Based on my own experience, I couldn't say how easy it is to find a good tuner setting because I've never found it unchallenging. Since 2017 with my first tuner, then a Lowey, I have tried with various levels of intensity without significant success. Various factors militated against me, not the least of which was an inconsistent approach with insufficient rigour in methods and a misapprehension of what tuners could actually achieve, but also less-than-consistent ammo, not to mention rifles with barrels that weren't especially responsive to the various tuners I've tried.

My current renewed interest is fueled by a new rifle with shorter, slightly slimmer barrel than the heavy-barreled models I otherwise shoot, together with the most solid front rest I've seen. The ammo question always remains. How good is sufficiently good enough for tuner use is a question that for me remains unclear. As you no doubt well know, it can be so difficult to obtain really consistent ammo, the kind which doesn't have a surprise or two (or more) in every box.

When you find that ammo, let me know. At this point, $$ plus almost no object, considering what I have already put towards 22LR precision.

 

[Leuchtkafer]

Yes the ammo equation sure is a bugger. Here in Canada it seems to be extraordinarily rare for any of us to lay our hands on an excellent lot. I don't suspect I've ever had the privilege. Much of what I've received would likely be graded as "average", and I've certainly encountered some absolute crap not even worth the price of admission. Here we are, trying to test for best performance, yet we are doing so without full knowledge of what our platforms are truly capable of and with ammo of questionable quality. I can assess a bellcurve of performance I expect from my rig after 5-6 years of shooting it, a bad lot of ammo is immediately evident to me with it. What would my rig do with an excellent lot? I'd love to see it. I've been able to achieve personal goals that seemed to be more of a happy coincidence that those rounds selected for the target were of sufficient consistency to produce what they did, bracketed by many other targets ruined by a few bad rounds.

I won't be one to develop a thorough and scientifically sound testing methodology for tuners, it is beyond my means. Like most others, I can do a limited amount of testing, then just have to "roll with" what seems to be the best option. I can play around a little here and there from that baseline and see if any further improvement is apparent, yet this is far from scientifically solid and takes place over an extended period of time. I know I can make the results worse than the naked barrel, for an absolute fact. Apparent improvement I'll take if it's getting me the results I want on paper.

 

[grauhanen]

When you find that ammo, let me know. At this point, $$ plus almost no object, considering what I have already put towards 22LR precision.

I would also pay much more for truly good ammo.

This season I've tested four different lots of Midas +, all produced in 2022, with one more to evaluate. (The three Center X lots that I have are disappointing.) Of these four M+ lots, as well as every other lot of M+ I've used over the years, none of them has been without surprises. Some have had more of them than others, but none has been exceptional. Every so often, perhaps when the stars are aligned, it's possible to get thirty or forty consecutive rounds that are remarkably consistent, but it can't be relied on to happen regularly or predictably.

 

[Williwaw]

My current renewed interest is fueled by a new rifle with shorter, slightly slimmer barrel than the heavy-barreled models I otherwise shoot, together with the most solid front rest I've seen. The ammo question always remains. How good is sufficiently good enough for tuner use is a question that for me remains unclear. As you no doubt well know, it can be so difficult to obtain really consistent ammo, the kind which doesn't have a surprise or two (or more) in every box.

I think you may have seen me say elsewhere that a surprise or two in every box is very consistent ammo. For the purposes of tuning I ignore them. The MV or some other aspect of these rounds is sufficiently deviant that no tuner can fix them. I operate a little lower on the ammo heirarchy than you but I feel I have had some great tunes on even SK Standard Plus. Thirty five of my 40 rounds would group very tight, tighter than one would generally expect and tighter than bare barrel. The other five cannot be tuned in.

I just polished off a case of Cx. It was nothing remarkable but on a calm afternoon and some good luck I got what I think are great results. Nevertheless 9 out of ten times I shot this ammo there were one or two or very rarely three errant rounds. This is part of the reason I like to by case lots. Once I establish a lot will do 398 then I'm just happy getting 398.

I'm unable to upload an image of the target I shot but the statistics for the 40 shot composite group are ctc ,405 and mean radius ,110 inches.

 

[Williwaw]

I was without electricity/internet for the better part of three days so I'm doing some catch up. Went over to SH and caught up on a tuner thread ... I despair for anyone new trying to figure out what is going on from that thread. Thus, I'm going to throw out something for you all to ponder and comment on.

Any lot of ammo has a velocity distribution of all rounds. Some are tighter than others(think SD) and some are more erratic(think ES). I think of that as a velocity profile. The profiles would be much more individualistic than the comparison of sd/ES only.

It seems pretty widely accepted that the tuner changes the pattern of barrel oscillation. Barrel oscillation can be thought of to have two components. One, a fairly regular, repeating sinusoid. Two, system noise that is generally lower amplitude and spurious although possibly occassionally intermittently repeating.

Tuning is finding the tuner/weight position that so alters and stabilizes the waveform that performance is improved. It follows that a different lot with a different velocity profile would require a different tune because the corresponding different exit times would find the barrel in other, less optimal positions. Because we are matching the velocity profile of an entire lot it can never be done perfectly but performance can be improved ... how much? Sometimes a little(hard to see and be certain) and sometime a lot(hallelujah).

Just to wade out into the swamp a little ways ... why would someones experience be that they can set it and forget it. There are many reasons ... they may not be skilled technicians, their equip might suck, adverse environmentals, insufficient testing OR given all of the foregoing they also buy higher end ammo that does not vary sufficiently lot to lot in order for them to detect the out of tune condition. If you lot test with the tuner on it only makes sense that you are searching for lots of similar velocity profile as that you previously tuned for. So you would become a leave it alone guy.

 

[grauhanen]

A tuner does indeed alter the barrel. It does nothing to the ammo itself. When the tuner is adjusted to the optimal setting, it should work all with good lots of ammo because of what it does to the barrel, completely independently of the ammo itself.

There are only a few settings withing the range of settings that improve results. Of these two or three, perhaps as many as four, one will typically be better than the others.

It's worth keeping in mind that what a graph of tuner settings and group sizes shows. As the tuner is adjusted out, there would be a more or less gradual change in group size from larger to smaller. In this regard, the settings that show improvement in group size don't occur arbitrarily. As an illustration of this, earlier in this thread the image below was posted. Centerfire rifles with tuners perform similarly.



There is nothing arbitrary about the best tuner setting or other settings that work well. One click more or less will not cause a significant change in results. Without causing controversy, many serious BR shooters say that with barrels that are between 24 - 26" in length and about .850 - .900" in diameter tuners will often have similar settings that are effective. Referring to Harrel tuners, these are said to be between 25 -50, 150 - 200 and around 400. Of course, specific barrel dimensions will necessitate specific settings. Additionally, factors such as bedding and shooting rest/set-up consistency may play a role in necessitating unique tuner settings.

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The idea a velocity profile is interesting, but it may at times be somewhat amorphous. Unless such a profile describes very good ammo with a very small ES and SD, it may be difficult to apply with some ammos, especially to those of an entry level match variety. Why? The lot sizes of these ammos is typically very large and can have a great deal of variation within a lot. Shoot enough boxes of the same lots of SK ammos and ES and SD figures will vary considerably.

This can also be observed in some lots of ostensibly "higher" tier ammos. For example, two days ago I chronographed one lot of Center X (2022 production). Over 50 rounds, it showed an ES of 41 fps and an SD of 9 fps. (For the general reader, that's not very good, but not necessarily surprising.) Today, another box from the same brick showed an ES of 31 and SD of 6. (These figures are much better for that grade.) In this lot, each box of ammo may require a different velocity profile; either that or the entire lot has a profile that is too broad to be meaningful. For anyone wondering how these two boxes of ammo performed on target, the first one was quite bad, and relatively speaking the second was quite a bit better. Same lot, different results.

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Set and forget? Consider the following with positive compensation in mind.

Imagine someone with a good rifle with a tuner at the optimal setting was shooting good ammo with an ES of 1055 fps to 1080 fps (or 25 fps). Positive compensation says the slower rounds will be timed to exit when the muzzle is highest on the wave or vibration. Faster rounds will exit when the muzzle is less high.

Now imagine the same rifle and tuner is shooting good ammo with an ES of 1040 fps to 1065 fps. Will the tuner cause the slower and faster rounds to exit the muzzle differently? No. Would it be different if the ammo ES was 1075 to 1100? (Note that it may be necessary to adjust the scope with ammos with different average MVs.)

Of course, more significant differences in POI would inevitably occur if the ES was large. There's only so much a tuner can be expected to do.

 

[grauhanen]

A further thought regarding ammo and tuners.

Assuming for the sake of argument (and simplicity) that positive compensation explains best how tuners function, when adjusted to the best setting the tuner influences the ultimate POI of the rounds. The result is that rounds with differing muzzle velocities will have a similar point of impact on the target.

Not counting wind, this requires that the MV is the key factor in otherwise determining POI. That is to say, faster rounds strike higher than slower ones. With the tuner, PC says that MV variation can be mitigated.

This would work well for ammos where an individual round's MV dictates where it will go. What about ammos that more frequently have characteristics other than muzzle velocity determines the POI of individual rounds? In other words, can positive compensation affect bullets that don't go where their MV predicts?

For two key reasons, poorer shooting lots of ammo, such as entry level match ammos (e.g. SK varieties) have more frequent incidences of rounds that have a POI that is compeletely unrelated to their muzzle velocity. This means that such lots will have more rounds that simply don't go where MV says they should. With such lots, the successful use of a tuner may be virtually impossible -- unless, of course, the errant rounds that don't have POI's related to MV are not included.