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April 5, 2018, 04:26 PM | #26 |
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Join Date: September 29, 2008
Location: Oregon
Posts: 2,346
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The problem with that page is only is examining extreme spread. Different groups can be in different locations relative to the point of aim. The calculations that estimator page is doing does not include any factor for where the group lies from the point of aim. Also, it is not factoring in how close the shots are to each other. Did you have four shots very close and one outlier? That is statistically very different than four evenly distributed shots within the extreme spread. That is why measuring just extreme spread is almost meaningless and not surprising that you can estimate extreme spread with a few shots.
But as hunters or target shooters when we say "accuracy' it is always in reference to how close to the point of aim. That is why a proper analysis of accuracy ought to measure the distance each shot is from the point of aim and relative to each other. A couple of software programs make this easy using photos of your targets: OnTarget and Shooting Lab. They both capture each shot relative to the point of aim and each other and calculate the average mean radius (distance from POA) and standard deviation. The mean radius is really what we are interested in if we want to know the most likely distance from the POA our bullets will strike. Both SW programs also allow you to overlay multiple targets to create virtual groups with the same POA. The resulting mean average factors in whether you have an excellent group with an outlier, or an overall mediocre group. So the above estimator only predicts the group size for any one group, but totally is incapable of telling you where any one of those groups will lie relative to the POA.
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"The ultimate authority ... resides in the people alone. ... The advantage of being armed, which the Americans possess over the people of almost every other nation ... forms a barrier against the enterprises of ambition." - James Madison
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April 6, 2018, 09:12 AM | #27 | |
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Location: New Hampshire
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Quote:
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April 7, 2018, 08:54 PM | #28 |
Senior Member
Join Date: September 29, 2008
Location: Oregon
Posts: 2,346
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Here is an example of OnTarget analysis graphic. The shot target was uploaded from a phone pic, then the bullet holes placed using OnTarget, a one inch distance was calibrated and the software calculates everything else such as: max distance C-to-C, mean radius, group center, offset from aiming point, maximum horizontal and vertical distance of bullet holes.
[Hopefully I can upload the image correctly]
__________________
"The ultimate authority ... resides in the people alone. ... The advantage of being armed, which the Americans possess over the people of almost every other nation ... forms a barrier against the enterprises of ambition." - James Madison
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