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Old 03-25-2015, 07:39 AM
Mozella
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Tuning a Barrel Tuner, My Take



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No matter how you believe barrel tuners work, everyone using a tuner is faced with the problem of finding the "sweet spot". Sad to say, this process is not as straight forward as, let's say, zeroing a scope.

There are many factors which might influence the exact setting at which a tuner works best. It seems obvious, to me at least, that finding that semi-mysterious setting by careful testing makes the most sense. Just because you don't understand physics, is no excuse for copying settings from another rifle or using a setting derived from some formula. Those methods are just plain silly.

Here's my approach, which uses science as it's foundation, but it isn't rocket science.

The problem most of us have is separating the normal variations effecting group size from the changes made by adjusting a barrel tuner. In other words, we're faced with the potentially daunting task of picking reliable data out of the background noise.

Now if you are a national champion shooter with high-end equipment and the very best ammo money can buy and you're testing in a ballistics tunnel, then good tuner data will be easier to extract. If you are a lousy shot using iron sights on an antique rifle using a mixed lot of old ammo on a windy day, then you're just wasting your time.

I prefer a variation of what is usually called the "Hopewell Method". The idea is to explore the entire range of tuner settings without spending a fortune on ammo while being able to finish the experiment before you die of old age.

In other words, you'll want to strike a reasonable balance. That balance won't be the same for everyone. Many folks advocate shooting two shot groups to begin with, but as a shaky old man using rather low-end equipment, I prefer starting with three shot groups. I print 20 targets, 1.5" in diameter, on card stock and use that for tuner analysis at 50 yards from a bench using an adjustable rest and a powerful scope.

As I gradually zero in on the best setting, I test a narrower band, in smaller increments, and (eventually) use higher quality ammunition.

My particular tuner, a Lowey from Australia, is graduated from 0 to 500 in a scale marked on the tube. The rotating threaded weight is marked with 50 gradations, so two full turns of the weight are equal to 100 increments. I prefer to make the first test in increments of 50; i.e. one full turn. You might prefer to shoot in increments of 100 to begin with, but that depends on your tuner. The idea is to identify which setting, or settings, merit further investigation. You don't want to waste ammo or time but you don't want to miss a promising setting either. I think 10 data points between the lowest and highest setting is about right.

Group size is easy to understand and measure. Simply eyeballing a set of groups will reveal a good deal of what we're looking for. But I'm not alone in arguing that measuring "average to center", also known as "average group radius" or "mean radius", is a better indicator of precision. It's the average distance of all the shots in a group from the center of that group.

Unfortunately, without the help of a computer, measuring mean radius is tedious to say the least. Fortunately, inexpensive software is available and cheap. I use On Target Precision Calculator which costs $12, but there are several others on the market. On Target allows me to scan my targets, mark the holes very accurately, and it will then calculate all the interesting parameters. I transfer the data to an Excel spread sheet for further analysis. If you have a scanner, I highly recommend you use a computer aided scoring program. It not only helps with adjusting a barrel tuner, it's invaluable when trying to find the best ammo for your gun. Gathering data is useless unless you can see and understand what it means.

My Lowey tuner has a permanent locating collar which is indexed to the tuner so that you can remove the tuner, clean the muzzle crown, and reinstall the tuner in the same spot. I recently moved that locator collar to a different place on the barrel; consequently, I had to re-tune starting from scratch.

Yesterday I shot two tests sessions. The wind was very light to begin with. That's important. I started with Eley Target ammunition, which my Savage MKII shoots well. You probably don't want to test with ammo lower in quality than this, but I don't think you need top of the line ammo either, at least to begin with.
Here is an Excel generated graph of session one.
Test One by Mozella55, on Flickr

It was obvious at the rifle range, just from eyeballing the group size, that settings around 150, 350, and 450 all showed promise. Later analysis proved this to be the case. Notice that I not only graphed groups size (Center to Center) but also mean radius (Average to Center) as well as Group Height. Tuners improve both horizontal and vertical precision, but most people (including me) think they improve the vertical to a greater degree. The On Target scoring software along with M.S. Excel makes it real easy to look at all three parameters at once. I think they're all important, but I put the most weight on Average to Center. You might prefer to concentrate on Group Height; suit yourself.

I shot additional three shot groups at the promising settings plus and minus 15 marks. An eyeball assessment at the rifle range showed that settings somewhere around 365 seemed to be very good, near 150 not quite as good, and near 450 probably not worth further investigation.
Test Two by Mozella55, on Flickr

But once I scanned the second card and looked at the data with more care, I realized that a single horizontal flyer at a setting of 150 made this particular setting look worse than it might actually be. This points out the difficulty of separating the data from the noise.

We've all shot cloverleaf groups followed by a group with a nasty flyer without changing anything. Every shooter I know has said, "What the Hell happened here?", while pointing to an aberrant target hole. In this second test, the Group Height at a setting of 150 was very good, but that one flyer made the Average to Center and the Center to Center measurement look pretty bad. The question is: Was it really bad or was it pilot error? Sometimes you launch a bad round and you know it while the bullet is still in flight. Other times, flyers are a complete mystery, especially if you're not a champion shooter. The lesson here is that you have to do some thinking and analyzing when you're doing this kind of testing.

Here is a chart of the second test results modified by moving that flyer closer to the other two holes of the group. The chart title has an error. It should read 150, not 200.

Test Two A by Mozella55, on Flickr

Had the flyer not been there, the data near a setting of 150 would be quite appealing. Note that on test one, a setting of 150 looked really good. Also, the shape of the three lines have similar shapes at all the test points except at this one data point. I suspect that flyer does not provide meaningful information. In any case, it seems unwise to completely reject this area based on a single three shot group with one flyer.

I called off my testing when the wind came up, but I intend to return to the range on the next calm day and test the two "good" settings in an effort to find the "best" setting. I'll first try to determine which of the settings are best; those around 150 or around 350. Next I'll narrow the search band and shoot 4 or 5 shot groups in an effort to gradually zero in on the optimum setting while increasing my confidence in the data. Finally I'll test a rather narrow band in small increments using Lapua Center X ammo. This is the same procedure I used when I first mounted the tuner.
Shooting about a third of my groups at less than .5 MOA with some .3 MOA groups a not-too-unusual occurrence while rarely shooting worse than 1 MOA while using Lapua Center X ammo (and not much worse than that using Eley Target ammo) is about the limit of my capability. If you're a really good marksman using high end equipment, you'll want to use something like Eley Tenex or equivalent for the last few tests.

The process is, for me, interesting and satisfying. If you're thinking about trying a tuner, I hope this post will assist you in finding your personal "sweet spot". When you're done, you should have some confidence that you've found the best setting because you've approached the process in a reasonable way given your skill level, budget, and available equipment.
  #2  
Old 03-29-2015, 08:17 AM
Mozella
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Tuning a Tuner, Day Two.

I moved the mounting position of the barrel tuner on my Savage MKII 22LR recently and had to go through the re-tuning process. Several members asked if I could post a follow-up to what I learned on day-one. I posted the initial testing procedure in this link: https://www.rimfirecentral.com/forums...d.php?t=579163

The following saga of day-two will make more sense if you read my initial post first.

Yesterday the wind was very light so (based on day-one data) I decided to investigate settings in the neighborhood 150 and 350. I started at 145 and worked my way up to 170 in increments of 5 while shooting four shot groups using Eley Target ammo. I also tested settings between 350 and 380, again in increments of 5 and 4 shot groups. This seemed a reasonable approach; however, someone else might prefer larger or smaller increments and perhaps more or less shots per group. To recap, on day-one I fired three shot groups starting with increments of 50 during test one and increments of 15 for test two.

As interesting data emerges, I like to increase the shots per group and reduce how far I move the tuner between groups. That helps build confidence in the data and helps insure that nothing gets overlooked.

Remember, you're trying to find good data hidden in the "noise" so you need to find a reasonable balance. For you fishing trawler types, you don't want to cast a net with too large a mesh and risk having the data escape. Likewise, too fine a net will gather so much that it will be too time consuming and too expensive to extract what you're looking for.

Here's the the first half graph of day-two, test one. I split the data into two segments, high and low, to better show the results of the test.

Day2EleyLower by Mozella55, on Flickr

Eyeballing the target at the rifle range indicated that a setting of 160 was good. However, after I got home and scored and graphed the data, it became clear that 145 was perhaps nearly as good, or at least worth looking at more closely. There was nearly perfect vertical stringing associated with 145 with all four shots touching each other. That's verified by the Group Height and the Center to Center data being equal; i.e. the green line and the blue line touch each other. Separation between those two lines, indicates a rounder group.

A better shaped group, to my eye at least, usually tricks me into thinking that it's more precise, when it might not actually be so. Furthermore, the Average to Center numbers are more important than group size when it comes to judging actual precision. But, as discussed in my earlier post, Average to Center data is very difficult to judge by eyeball and measuring it by hand and doing the calculations is tedious. Thankfully, scoring software makes it child's play, but I must spend a few minutes with a scanner and computer at home before I can enjoy the benefits.

The point is that eyeballing group size and shape at the range and making a decision without the benefit of extracting the Average to Center data and taking a closer look at Average to Center data might lead you astray. It certainly did in my case. Is there a better setting below 145? That answer will have to wait for another day.

Day2EleyUpper by Mozella55, on Flickr

Settings in the mid-300s showed promise on day-one but not so much on the first test of day-two. It wasn't bad mind you. More than half the groups in the range between 350 and 380 were sub MOA, but I didn't notice any really impressive groups and the graphed data confirms that. What you want to see is a dramatic valley, preferably in all three lines, indicating a potential "sweet spot".

For the second test target I switched to Lapua Center X ammo. At this point I'm getting down to fine tuning and I didn't want an occasional out-of-spec round confusing me. Eley Target is pretty good ammo, but the Lapua Center X is less likely to throw a wild round. Previous testing had indicated that it performed, in my cheap Savage MKII at least, much like a good version of Eley Target. That is to say, the point of impact was about the same, but the groups were noticeably tighter. Of course, for the price difference, Center X better make smaller groups.

Again I used four shot groups but this time I used increments of 3 between 155 and 164 and again between 355 and 364.

Here's what the left and right end of the second test looked like. Again, I split them so that the data is easier to interpret.

Day2LapuaLower by Mozella55, on Flickr

Day2LapuaUpper by Mozella55, on Flickr


Notice that using the Center X ammo, the lower settings produced data which graphed as a set of rather flat lines. There was no obvious "best setting" in this area. But the upper settings showed a dramatic valley at 361 and nearly as good performance at a setting of 364. Plus, the separation between the Group Height line and the Center to Center line indicates a rounder group. Note that the smallest 4 shot group of the day was .061", less a sixteenth of an inch at 50 yards. Doing that all day long would make most people happy. But, of course, this impressive group begs the question. It is a genuine sweet spot? And if so, is it only good for Lapua Center X? Or is it just dumb luck? I'm not placing any bets just yet and you shouldn't either.

By this time the wind started blowing and I suspended my data collection. Plus, I'm not smart enough to make solid decisions without scoring and studying the information I had gathered.

So where do I stand? Well, I have some strong hints, but nothing to take to the bank just yet. Questions remain.

Are settings below 145 worth looking into? I would say yes even though, after looking at the other data, I doubt if there's really anything there.

Is the good performance around 361 a result of a "sweet spot" or as a result of the Center X ammo just being so much better than the Eley Target? Hard to say. It's entirely possible that 361 is a genuine "sweet spot" for Center X while some other setting could produce nearly as good results with Eley Target. That question remains to be answered later.

So what's next? Well on the next calm day I'll want to confirm settings a little bit either side of 361, possibly with 5 shot groups and tuner setting increments of 2. At the moment, I've got a strong suspicion that 361, or very near to it, will prove to be my normal tuner setting. I'll want to confirm it with Center X and then revert back to Eley Target to see if the best setting will work for both brands of ammo. If it does, I'll further confirm that data by testing some Eley Club, Eley Match and Eley Tenex I have on hand.

I think I might also take another look near settings of 160 and then have a peek at a setting of 140 just to satisfy my curiosity.

Some folks might consider all this way too much work; I get it. But for me, being satisfied shooting 0.500" groups in a 50 yard target seems lazy if there is a real possibility to find a way to shoot 0.200" groups.

If you find yourself bored at your local rifle range, get yourself a barrel tuner. It will provide years of head-scratching entertainment.
  #3  
Old 04-01-2015, 09:37 AM
Mozella
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Tuning a Tuner, Day Three Conclusions

If you read my two earlier posts in this area of the forum, "Tuning a Tuner Day One" and "Tuning a Tuner Day Two", you'll know that my goal yesterday was to confirm that a tuner setting near 361 on my Lowey tuner is the "sweet spot". Based on my gross testing on day one and after examining two promising settings on test day two, I was expecting to home in on the best setting yesterday.

I'm happy to say, I met my expectations. Here is the chart of group size, mean radius, and group height for 5 shot groups at 50 yards using Lapua Center X ammunition for ranges between 359 and 362 in increments of one mark (the Lowey doesn't have real "clicks").

Day3 Lapua Upper by Mozella55, on Flickr

If your local gunsmith were being paid to set up your tuner, this would be the end of his story. He would shake your hand, cash your check, and have confidence that you would be a happy camper. And there is a high likelihood that you would indeed be quite happy.

But there is more to the story because this is my tuner, I did the testing myself, and I know the whole ugly truth. Plus I don't have an overwhelming urge to post lies even though this is the Internet. The truth will do just fine even if it isn't quite so neat and tidy as a good lie.

Yesterday I shot a total of 19 groups under near ideal conditions, using Lapua Center X ammunition for the "formal" part of the test. After that, I went on to confirm the best settings using Eley Club, and Eley Target. Soon after that the wind came up and I quit testing because I didn't want to contaminate my data.

Nine out of ten best groups (Center to Center) were shot near a setting of 360 as well as eight out of ten best "mean radius" (Average to Center) and eight out of ten best Group Height measurements. Clearly, 360 is the "best setting", right?

Not so fast Hoppe's #9 breath. Here is a chart of testing the tuner settings around 145.

Day3 Lapua Lower by Mozella55, on Flickr

The Baby Ruth candy bar in the punch bowl is the fact that the best group of the day was shot at a setting of 145. Dang! What's more, the worst group of the day was shot at 360 while trying to duplicate the good group shot at that same setting a few minutes earlier. Double Dang! So why isn't a setting of 145 the "sweet spot"?

It boils down to picking the fly s**t out of the pepper. We've all shot bad groups and blamed it on the wind, or had an otherwise-nice-group spoiled by a wild flyer in which case we often blame the ammo. But when we put five shots in one hole, the shooter nearly always takes full credit for his great marksmanship. So should I seize upon the one great group at a setting of 145, where all five shots went into one ragged hole, and claim that it defines the "best" sweet spot? If I'm honest, "no" is the answer and here's why.

Look at this bar chart comparing the average of the three most important parameters at high (around 360) settings and low (around 145) settings. In every case, the higher settings are clearly better on average even though the single best group of the day was at 145; remember lower numbers indicate better performance.

Day3 Performance by Mozella55, on Flickr

I consider the very good group at a setting of 145 to be an anomaly similar (in reverse) to a nice group ruined by an unexplained flyer. For some reason, I just got lucky. Nevertheless, it is real data collected just like the other data. The importance of this particular data point must be tempered by the fact that I could not duplicate the "single hole" group at a setting of 145. But I could put five holes into one slightly larger hole at a setting of 360 and I did so several times during this test.

So what does it all mean? Without the scientific equipment to actually observe and measure what happens when I fire my rifle, I think I can lean on my engineering background to make a reasonable guess. I'm one who believes that firing a round causes forced distortion of the barrel which is different from the sustained harmonic vibration remaining after the bullet is long gone; just as plucking a guitar string is different from the sustained note that string plays after you release it. If the goal is to have the bullet exit as the barrel is moving upwards and/or bending upwards, then it's certainly possible for that condition to exist at two different tuner settings.

We know that the barrel will distort in several different modes. How those modes interact in my rifle/stock/scope combination is unknown, at least to me. They may interact to partially reinforce each other or partially cancel each other; I really don't know. Keep in mind, we're talking about my rifle only of course. If a setting of 140 produces a favorable barrel position, that would not be unexpected. Could that have matched up with 5 consecutive rounds of Lapua Center X ammo with exactly the same velocity so that they all entered the same hole at 50 yards? Perhaps; Center X is pretty decent ammo.

But careful study of the data shows that, on average, performance at a setting at or very near 360 is better. In other words, I have identified two "sweet spots", one of which is "sweeter" than the other if you average the data. This may or may not be the norm for other rifles and tuners. I don't have enough experience with tuners to say one way or the other, but my engineering background tells me not to rule the idea out. There is at least one guru on the net who denies that there can ever be two good tuner settings, but this person is not formally educated and hasn't offered any proof other than his claim.

There is no need to dwell on this point. The idea is to find the "sweetest of the sweet spots", right? Just don't be surprised if, when you set up your tuner, you see data which shows more than one favorable setting. Your job is to test carefully so you can determine which is the better one.

I am pretty sure a setting of 360 is best for my gun. Interestingly, the data reveals more information. I can see there is a gradual fall-off in performance at a range of settings a little bit higher and lower than 360. In other words, rather than a sharp notch in the data resembling a steep canyon, my graph shows a gentle valley with 360 at the bottom.

Does this mean that I've found a bighearted setting which will work well for several kinds of ammo and/or several bullet velocities? I hope so, but I'm not at all confident that I can make that claim without doing more testing including testing with a chronograph. In fact, the friendly, non-critical way my tuner acts near a setting of 360 might mean nothing whatsoever.

Your tuner and gun combination might be the opposite of mine. In other words, your rifle's performance might degrade sharply on either side of your "sweet spot". That's for you to discover.

Don't forget, the more groups you shoot the more likely you'll develop a spread in your data. Consider not only the averages but the best and worst too. Here's a chart showing just such information.

Day3 Group Size by Mozella55, on Flickr

Eley Target ammo has the best average because I only shot two groups with it and maybe I was a little lucky or maybe my rifle really likes Eley Target. Center X, the best ammo, had the worst average because that's what I used for most of my testing and sooner or later I was bound to fire a couple of less than great groups.

If you look at the best group from each brand, you will see that the "good stuff" is indeed the "good stuff". The lesson here is to be wise when you sort and examine your data.

Bottom line: I'm satisfied I have a good setting for my particular rifle and tuner. I'm also convinced that my skill level and cheap equipment is not likely to tease a more conclusive result out of this batch of testing. Remember, I'm an old guy with a bad shooting eye using one of the least expensive rifles on the market, a relatively inexpensive scope, and quite ordinary bench rest equipment. Those conditions will produce a certain amount of noise which I suspect will hide future revelations. But I could be wrong. I'll continue to gather and analyze data as I always do and perhaps, in time, the averages of many hundreds of rounds will show some kind of useful trend.

In any case, my cheap little rifle shoots pretty well. Even after including groups produced at other than optimum tuner settings, sixteen of nineteen 5-shot-groups I launched yesterday were less than one MOA and eight of those were less than 1/2 MOA. Even the worst group, mysteriously shot at a setting of 360, wasn't all that bad.

The average size of 19 groups, 5 shots each, was .394" which I consider acceptable. When I shoot good ammo at the best setting, I expect half my 5 shot groups to be less than .300" at 50 yards or perhaps even better.
If I were hunting squirrels (which I'm not), I would be putting meat in the pot. I' m an old fart and I need just enough accuracy to keep the neighborhood kids off the lawn. I prefer to shoot 'em in the iPhone.
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