Do you use On Target with M.S. Excel?

[Mozella]

If you use On Target scoring software and store the results using an M.S. Excel spreadsheet, you might find this helpful.

My main interest is shooting 600 yd F-Class and 600 yd BR. I collect and study a good deal of test data in an effort to improve overall precision. It's hard to know where you're going if you don't know where you've been. And, as Yogi Berra said: "If you don't know where you are going, you'll end up someplace else.”

Naturally, I keep track of Center-to-Center group size. However, I believe that Mean Radius (also known as Average-to-Center or "ATC") is a more meaningful measure of precision than the ubiquitous CTC measurement. Mean Radius is tedious to calculate by hand, but the On Target Precision Calculator computer program ($11.99) does it automatically. Of course, Mean Radius measurements can be converted to MOA just like CTC group size.

We know instinctively that shooting a certain MOA at 600 yards is more difficult than shooting the same MOA at 100 yards; but how much more difficult is it? Likewise, the more shots in a group, the larger the group tends to be. Just how much larger can we expect a ten shot group to measure when compared with a three shot group?

Those two questions are answered in detail in Bryan Litz's new book MODERN ADVANCEMENTS IN LONG RANGE SHOOTING.

Because I have data collected at different distances and with differing numbers of shots per group, direct comparison is difficult. A 5-shot group which measures .930 ATC @ 600 yards just doesn't jump out at me as better than a 4-shot group measuring .105 @ 100 yards. My goal was to convert all the apples and all the oranges to peaches so that the various Mean Radius values would make sense.

Consider the sample Excel file. The formula in column Q, labeled "ATC Corr" normalizes the Average-to-Center measurement from column M by using factors from the target distance and number of shots per group.

A few caveats: As everyone knows, converting measured group size to MOA is exact and simple for both Center-to-Center and Mean Radius (ATC). Deciding how much a group size grows when you increase the number of shots per group is not as easy, but can be estimated with reasonable confidence. But group dispersion vs. target distance is a different kettle of fish.

It should be obvious that a champion F-Class or BR shooter will produce groups that suffer less dispersion at long ranges than my groups if for no other reason than he has better wind-reading skills. Other factors come into play too. Those interested in such things should consult Mr. Litz's book for more information. My formula is not perfect and Math/Excel experts will likely consider it clumsy. Neither is it universal since it is slanted a bit toward the way I shoot in addition to being reflective of the data gathered by Mr. Litz. He used a year's worth of data from a BR club as well as some F-Class test results from the U.S. Rifle team. In short I took his tabulated data from both disciplines, blended it with my collected data, and using brute force I found a way to warp and tweak my Excel formula cell to more or less match that data.

A peaches-to-peaches comparison (even if the peaches aren't perfect) is certainly an improvement over apples-to-oranges, especially when it comes to the slightly obscure Mean Radius data which many of us find more difficult to visualize than Center-to-Center group size. Now when I look at the corrected ACT data I can get a feel for how my latest 600 yd BR group compares with the data I gathered when I tested that load recipe at 100 yards.

If you keep track of your collected data using Excel, copy the formula from column M and add it to your Excel work sheet, making sure the cell references match your particular spreadsheet. It should be reasonably accurate between 100 yds and 1000 yards for groups with between 3 and 10 shots per group. If you try it, report back with the results.

 

[CharlieNC]

I typically do 10 shot practice on a F target. To track my progress (or deterioration) I note both the raw score, and the adjusted to center score by simply over laying a clean target over the group. This accounts for not being able to see the holes in real time, or having them marked as in a match. In addition the horizontal and vertical spread are noted. Now to your question, I have been studying the statistics of target scoring. Initially I liked the mean square radius approach, but it is woefully inadequate because it does not describe what most of us usually see; that is the horizontal is typically much worse than the vertical variability. I will soon have a statistical summary completed to account for this. In the meanwhile the score including X count do a good job for both tracking, and judging changes in my shooting procedures.

 

[Mozella]

Please post your statistical summary when you have it completed. I'd love to see it.

As you know, the problem with the typical F-Class match is that unless you're using electronic targets, you typically don't get any feedback from the target itself. You get only the score. The score is important of course, especially since that's how the winner is determined, but it's not easy to compare an F-Class score with a BR group size.

For example, if you put 19 shots in the same hole on the far right side of the 10 ring with one shot just a bit further right which scores a 9, you would have a fine BR group. But the guy who puts all 20 shots scattered around inside the 10 ring would beat your F-Class score even though he would not do as well shooting the same group in BR.

I suppose that's part of what makes F-Class appealing; that combination of precision and accuracy. Now if I could just move to some place without any wind, I'd be all set.

If you find a nifty way to compare a score with a group size, that would be very interesting to me and others too.

 

[dmoran]

Please post your statistical summary when you have it completed. I'd love to see it.

As you know, the problem with the typical F-Class match is that unless you're using electronic targets, you typically don't get any feedback from the target itself. You get only the score. The score is important of course, especially since that's how the winner is determined, but it's not easy to compare an F-Class score with a BR group size.

For example, if you put 19 shots in the same hole on the far right side of the 10 ring with one shot just a bit further right which scores a 9, you would have a fine BR group. But the guy who puts all 20 shots scattered around inside the 10 ring would beat your F-Class score even though he would not do as well shooting the same group in BR.

I suppose that's part of what makes F-Class appealing; that combination of precision and accuracy. Now if I could just move to some place without any wind, I'd be all set.

If you find a nifty way to compare a score with a group size, that would be very interesting to me and others too.

Mozella -
Your mistaken or worded it wrongly:
In LR-BR, it is shot for both Group & Score, which is for both precision & accuracy.
Unlike F-Class that is only for Score, which is for accuracy only, not precision.
Donovan

 

[Mozella]

Mozella -
Your mistaken or worded it wrongly:
In LR-BR, it is shot for both Group & Score, which is for both precision & accuracy.
Unlike F-Class that is only for Score, which is for accuracy only, not precision.
Donovan

You're correct, I didn't make myself clear. Where I shoot, the BR winner is determined by group size alone. Five shots in a small group anywhere on the target is the winner even if the score is the worst of the match. Distance from the center X (i.e. accuracy) has nothing to do with winning; i.e. shooting out the X is no better than a tiny group right at the edge of the paper. Of course I'm aware that second place is determined by score, but some people call that "the first loser"

And you're correct when you say F-Class finishing positions are determined strictly by score; however, the score is not determined by how accurate the shooter is. Score depends on where the bullets hit. For example, distributing a perfectly centered array of 20 shots in the 7 ring may be perfectly accurate (i.e. zero offset) but it will not beat 20 shots in the 8 ring with a 3" offset from the target center, a less accurate but higher scoring string.

Said another way, an F-class winner, at least where I shoot, must display a combination both pretty good accuracy and pretty good precision. Neither factor need be the best of the day, but generally speaking it takes being pretty good at both to win. First place in F-class depends on score but contrary to what you say, score is not determined by accuracy. Score and accuracy are related of course, but they are two different things.

Where I shoot 600 yd BR, the match is quite often won by a shooter who doesn't have the best score because accuracy is not relevant as long as it's barely good enough to get all five shots on paper. The fact that both accuracy and score are completely ignored when determining the winner is why I consider 600 yd BR a precision game.

I hope I've clarified my previous post.