What should a tuner be expected to do?
- Thread starter grauhanen
- Start date
And finally I added setting 55 to see how it fit in. This is a 35 shot group under 1/2 inch.
Looking at the sdx and sdy there is .023 inches excess vertical. I assume that horizontal and vertical dispersion would be equal if all MV was constant for all rounds. With just .023 inches of vertical a significant component of MV SD is not evident at the target even though it was present at the muzzle.
Go back and look at how much higher 55 is than 50. A series of consecutive settings on the waveform upslope would be expected to produce a POI rise. Of course I am only speaking of a PC tune.
Some may not like my assumptions but they have proven to have utility even if not perfect ... they have worked for me. Today I shot for score using setting 51.
OnTarget can be used to kick out an ARA UL score which I scaled back from 35 to 25 rounds and this would be 2100.
I feel like I should say something about my gear. Vudoo 360, 22 inch ACE kukri, Foundation stock, BnA comp trigger, NF 15-55, Harrell tuner with added weight(380 grams total). I'm prone using a Rempel, rear bag is a coat sleeve full of rice and I only touch the trigger. Six primitive wind flags on a dead still night.
Ammo is Lapua CenterX, a blind lot.
Looking at the sdx and sdy there is .023 inches excess vertical. I assume that horizontal and vertical dispersion would be equal if all MV was constant for all rounds. With just .023 inches of vertical a significant component of MV SD is not evident at the target even though it was present at the muzzle.
Go back and look at how much higher 55 is than 50. A series of consecutive settings on the waveform upslope would be expected to produce a POI rise. Of course I am only speaking of a PC tune.
Some may not like my assumptions but they have proven to have utility even if not perfect ... they have worked for me. Today I shot for score using setting 51.
OnTarget can be used to kick out an ARA UL score which I scaled back from 35 to 25 rounds and this would be 2100.
I feel like I should say something about my gear. Vudoo 360, 22 inch ACE kukri, Foundation stock, BnA comp trigger, NF 15-55, Harrell tuner with added weight(380 grams total). I'm prone using a Rempel, rear bag is a coat sleeve full of rice and I only touch the trigger. Six primitive wind flags on a dead still night.
Ammo is Lapua CenterX, a blind lot.
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There is much value in measuring groups as you implicitly suggest. When shots in a group are evenly distributed within a circle encompassing all of them, the width of that circle is a reasonable yardstick. When shots are less evenly distributed in a group, the diameter of the circle encompassing all of them becomes less representative as a yardstick.
As a result an "average to center" measurement is potentially more useful (there may be a more appropriate term currently in use). It measures the distance of each round from a center. When many shots in a group are relatively close together and there are only a few shots that are less close, the average to center measurement would reflect that more shots were close together in a group. To give an example, assume that the groups shown are the same overall size. One of each pair may be preferable.
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As I understand, the actual average to center calculation can be made with the On Target program refered to by Williwaw. I have the program but lack the technical enthusiasm to use it with any regularity.
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You're saying that groups 46 through 59 show a good tune -- excluding the high left impacts on groups 51 and 58?
At this point I haven't shot this lot enough to really know what it will do, either with or without a tuner. The target you turned right side up is promising in that there is a wide range of consistent grouping with a relatively stable and rising POI but not super tight. This is really a demonstration of my method and observations rather a definitive quantification of the effect of a tuner on this lot of ammo.
It is quite fortuitous that 37 to 42 are on that same target. At this point, when prospecting for a tune they are also confidence builders when compared to the 49-52 range.
Full disclosure here, I will likely never shoot this ammo without a tuner enough to really quantify the difference. My interest is in shooting .576 inches ctc or less for 40 rounds centered on the bullseye.
It is quite fortuitous that 37 to 42 are on that same target. At this point, when prospecting for a tune they are also confidence builders when compared to the 49-52 range.
Full disclosure here, I will likely never shoot this ammo without a tuner enough to really quantify the difference. My interest is in shooting .576 inches ctc or less for 40 rounds centered on the bullseye.
Mystic Precision
CGN Ultra frequent flyer
- Location
- Summerland, BC
I think this is why tuners can be so polarising... many shooters HOPE a tuner will make things better. It will not.
All it does is modify the vibration of a GOOD AND ACCURATE BARREL to better work with a GOOD AND ACCURATE BATCH OF AMMO (the pricey stuff). If the barrel is not capable of itty bitty accuracy, tuners will not help... adding oly level ammo will not help (but might help it suck less).
conversely, the best benchrest set up using CCI blaser is not going to win any matches even with the latest greatest most shiney tuner.
I use a tuner to coerce a happy marriage between two very capable systems.. that don't seem to want to get along without that help.
It really is that simple... at least for me.
Jerry
When using any ammo that is itself inconsistent, it may become impossible to know with certainty whether it's the ammo variation or the tuner that's responsible for the results.
I've done some tuner testing using ammo that without a tuner has produced as many as ten consecutive five-shot groups that are sub-MOA (sub-.500") results at 57 yards (my range's version of 50). Many shooters might think that level of consistency is "good enough". But I've found that level of ammo consistency is unsatisfactory as the results remain frustratingly inconclusive.
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What level of ammo consistency is needed for successful and repeatable use with a tuner?
Many position, prone, and BR shooters use a guideline for ammo evaluation when evaluating results at ammo testing facilities that's similar to the following for ten-shot group averages at 50 meters measured outside-to-outside in millimeters: 12mm or less is excellent; 12 - 14mm is good; 15 - 16mm is "meh" or uninspiring; 17 - 18mm is poor; anything larger is unacceptable.
In terms that may be more familiar to many shooters, 12mm outside-to-outside = .25" center-to-center; 14mm = .32" ctc; 16mm = .41" ctc -- for ten-shot group averages.
If tuners work best with ammo that's at least "meh" level (16mm oto) or .41" ctc or better, I suspect few shooters buying ammo in Canada would be reporting consistent and repeatable tuner use because ammo that consistently at least that "good" doesn't seem easy to find.
Put another way, if your best ammo will not shoot five ten-shot groups at 50 that average under about 16mm oto or .410" ctc, it may be an unproductive use of resources to try to find a tuner setting that works consistently and repeatably.
Of course the other side of this is that tuning depends on some degree of inconsistency to work and if that inconsistency did not exist there would be no reason to put a tuner on a rifle.
For me the question becomes how much inconsistency in MV can be successfully tuned for. I think it would be different for every barrel, tuner, etc. My experience is that a lot of SK that is shooting well for me can be more easily tuned for and sees more improvement than the CenterX that I have had. I have no experience with higher grades of ammo which we hope would need less massaging and therefore a finer eye to tune.
I wouldn't expect that the stuff Lapua ships to Canada is any lower grade than the rest of the world gets. We don't have the benifit of the test centers but the majority of Americans don't get there either though I expect many top competitors do. That said, .410 ctc 40 shot composite groups are not unknown to me. I looked back in my pile and the last one was three or four days before I went down this tuning rabbit hole with a new case lot.
As you know, the only inconsistency with which a tuner can contend is MV. But ammo inconsistency is also caused by other factors which tend to be seen more often with entry level grades of match ammo. That's why these ammos are more affordable. At the same time of course, there's nothing to guarantee that more expensive grades of ammo don't have these issues from time to time.
I also wouldn't expect the Canadian market to be shipped any Lapua that is less consistent than is available elsewhere. I'd prefer to think that the lots we get in Canada are no worse than those shooters obtain in Europe or elsewhere. But what I prefer rarely matters. There may be reason to wonder if some places see poorer lots of Lapua than others.
It's more than never seeing a lot of Midas + that didn't have flyers. To illustrate, consider the following ammo that's been tested in several rifles with similar results. Over the chrony several boxes of one lot of Center X showed it had an ES over 80 fps, with SD figures in the high teens. That kind of CX shouldn't exist let alone be sold. It was the poorest shooting lot of Lapua I've encounterd. By comparison, the most consistent lot of CX I've used had ES figures in the high 20's with an SD figure of 6 fps. It performed well on target. I tested a lot of X-Act that had an ES over 50 fps with an SD as high as high as 11 over a box. That lot of X-Act shouldn't exist either. Of course, these are outliers and the great majority of Lapua lots I've had perform on target and over the chronograph as expected.
Regarding forty shot groups at 50 under .500", readers should try shooting several ten shot groups with the best ammo available. Measure each group and see if they average under .410". If they do, it may indeed be "meh" (or better) ammo after all.
My experience is that I can't get below .400 for forty shots. That is a little tougher then four 10s averaging 400. I much more often see sub .500 for forty shots with an mean radius of .125. My shooting has been about 50/50 SK/Cx. The result below is that last case lot of Cx that I shot up before launching my current tuning saga. This thread has me thinking I might shoot up a 6 or 8 bricks of different lots of Cx to see what it does without a tuner. Either way I'm pretty happy with my little repeater with the house brand barrel.
I don't know whether to use the difference in the width to height or SDX and SDY but in either instance the excess vertical(my definition, vertical dispersion due to MV variation resulting in dispersion greater than horizontal dispersion) is pretty minimal. Certainly a fraction of what G. has been seeing on his chrony. My explanation is a PC tune.
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Thanks for the encouragement. Grauhanen and I are sort of known entities to one another so it's great to get wider input. I have to preface everything I say with the proviso that I have absolutely no relevant experience at any distance beyond 50 yards.
Before I go fishing I have a question for you. If you chrony or know shooters that do, what is the relationship between what a calculator would predict and what you observe on target?
... two fish later
That looks like a stupid question to me. I expect your calculator lines up sufficiently with your target to get you hits. What I'm really wondering is how consistently slower rounds are actually low and vice- versa. To build this incrementally lets start at 100 yards. What is a typical group size?
Before I go fishing I have a question for you. If you chrony or know shooters that do, what is the relationship between what a calculator would predict and what you observe on target?
... two fish later
That looks like a stupid question to me. I expect your calculator lines up sufficiently with your target to get you hits. What I'm really wondering is how consistently slower rounds are actually low and vice- versa. To build this incrementally lets start at 100 yards. What is a typical group size?
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Jonnyofalltrades
Regular
- Location
- North-central Saskatchewan
It's not always the ammo's fault. I remember seeing ES of almost 100 fps out of target ammo(brand escapes me at the moment). Switching rifles, the same box started showing 15 fps ES.
The barrel with the wild spread was a custom "tight bore". Not sure if that had anything to do with it.
I've tested over the chrony most extensively with two different .22LR rifles over three seasons, with a third beginning this summer.
Some "target ammo" can be quite capricious over the chronograph, with considerable variation within the lot. These are usually the most entry level grades of .22LR match ammo. It should also be noted that when chronographing 22 ammo, shooters should always use as large a sample size as possible to avoid unreliable data. For example, a ten shot string with an ES of 15 fps is possible with ten random rounds out of a box of fifty that itself has an ES that's considerably higher. It's just the luck of the draw, so to speak.
To illustrate with an example, see the target below. The ES for each group of this poor lot of CX is shown. If the first group only was chronographed, a very good ES of 17 fps would be shown. But clearly that wouldn't be reliable data for this lot, which over an entire box had an ES of 83 fps.
The observation that the bore itself plays a role in what's seen in the chronograph results is sound. In my testing I've observed that the same lots of ammo can have different average MVs in different barrels that are the exact same length. That is to say, some barrels/bores of the same length and make are faster or slower than others.
With regard to ES and SD figures, they've been quite similar with the same ammos over two, and now three, rifles. The caveat remains that some poorer shooting lots of ammo, including some very recently tested 2022 vintage Lapua Center X, can have different results from one box to the next with the same rifle.
So this is just an opinion, not my experience. If I was going to give this a try I would pick my day carefully. I would be suspicious of a 'calm' day because I have seen too many times when lazy moving but incoherent/contradictory flags are a bad sign. Yet a light, steady crosswind can allow for some quite repeatable results. To begin with I would set very modest expectations for tuning for longer ranges.
Your specific question is whether the difference would be easier to see at greater distances and I'm going to say no. That is based on my belief that the effect of various unknown and unquantafiable causes of dispersion increases disproportionally with distance while the PC compensation can only be predicted/expected to be what the calculators/physics tells us. That is not a bad thing because what we are trying to measure is not too small to measure at 50yards.
I am certain that it was Kolbe who suggested that his work at Border Barrels(UK) showed that the barrel movement he was observing was too little to effect PC at 100 yards. Of course in theory a PC tune at 50 is insufficient at 100 but it is better than nothing. When you think of it it is quite a coincidence that barrel oscillation harmonics are actually near enough to right to be exploited for the purpose we are addressing. There is no end of enthusiasm for tuning yet blessed little solid science in barrel movement. It stretches credibility that a handful of fairly arbitrarily designed tuners can be made effective over the broad range of barrel lengths, diameters, tapers, metallurgy,etc. That said, I think a case can be made for tuners because there can be no argument that they affect results and most often with some work we can get it to where there is improvement.
My dream is for some one with an engineering background to use modelling software to design a barrel/tuner combination that is matched for PC. Then all I would have to do is tweak the tuner to compensate for the minor inherent differences that would inevitably arise ...
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Although the question may not have been asked of me, I can offer some examples that may help illustrate differences that can occur between POI on target and POI as expected by MV.
Although exact numbers are impossible to calculate, it can be said that even with entry level match ammos (e.g. SK varieties, Eley Club/Sport/Target and RWS Target Rifle, Rifle Match) and more usually with higher tier varieties, POI on target is related to the MV of the round. That is, faster rounds strike higher, slower ones lower.
But that doesn't always happen and when it doesn't it's more often with less expensive varieties of ammo such as entry level match ammos. But it can also happen with higher tier varietes, but perhaps not as often. There are two main reasons why a .22LR bullet's POI doesn't always match what its MV would predict, but they can be discussed in another post if anyone's interested.
When calculating POI based on MV, it's helpful to keep in mind that at 50 yards, a ballistics calculator will show that a 10 fps difference in MV between two rounds results in about .018" -- call it .02" -- of vertical dispersion. At 100, a 10 fps difference yields about .27" of vertical. When there's a 20 fps difference in MV, the difference between two rounds at 50 is about .038" -- rounded to .04". At 100 it would be about .54" of vertical.
Below are a couple of targets shot with a poorly shooting lot of Center X. The distance was 57 yards and the conditions were calm. The ES of each group is writtten on the target and some individual round's MV is shown. Note that not all the faster rounds in a group struck highest or the slower ones the lowest.
This is a very poorly performing lot of Center X ammo.
Below is another lot of CX that's a little better (but still not good). It has fewer incidences of POI and MV not mismatching.
Differences between expected POI based on MV and actual POI on target can be very easily seen at 100 yards.
Compare the following targets from two years ago. Note that group size (especially in the vertical dimension, which isn't shown but can be estimated by the viewer) doesn't always match a group's velocity spread. That is to say sometimes large groups may have a smaller than expected MV spread or vise versa.
The targets below were shot with SK Rifle Match.
Compare the following targets from two years ago. Note that group size (especially in the vertical dimension, which isn't shown but can be estimated by the viewer) doesn't always match a group's velocity spread. That is to say sometimes large groups may have a smaller than expected MV spread or vise versa.
The targets below were shot with SK Rifle Match.
Faster rounds don't always strike higher than slower rounds. These kinds of irregularities can occur with other grades of ammo.
Below is a target shot with X-Act (an inconsistent lot of Lapua's top grade). Note the varying ES of each ten shot group.
Center X below. CX lot ending with 777 is the poorest performing lot of Lapua ammo I've seen.
Below is a target shot with X-Act (an inconsistent lot of Lapua's top grade). Note the varying ES of each ten shot group.
Center X below. CX lot ending with 777 is the poorest performing lot of Lapua ammo I've seen.
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