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ES and SD
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<blockquote data-quote="Greyfox" data-source="post: 1433886" data-attributes="member: 10291"><p>SD isn't really an average of the velocities of shots fired, as that would be the "mean"(or average), the number you would plug into your ballistic calculator for MV. This is the sum of all your velocities divided by the number of shots. ES is the extreme spread between the lowest and the highest velocity in a string of shots. SD is "standard deviation" which is a formula that calculates the distribution of the individual shots and produces a value that represents a confidence level where 95% of your fired shots will fall within a given range. The SD (as shown in the output in chronographs like the Magneto Speed, Oehler, etc.) can generally be multiplied by 4 to give you an approximation of the velocity spread where 95% of your shots will fall within this range. For example, an SD of 5 is approximately 20FPS, where you can expect 95% of your shots to fall within this velocity range. For my LR hunting to 1000 yards I shoot for an SD of 5-10, or an ES that's less then 30FPS. This may sound high to some but it uses a sufficient sample of shots of shots(+20), and applies to the range of temperatures I expect to hunt. This value will keep my shots in the vital area of a whitetail/antelope out to 1000-1200 yards with my particular load, other factors considered.</p></blockquote><p></p>
[QUOTE="Greyfox, post: 1433886, member: 10291"] SD isn’t really an average of the velocities of shots fired, as that would be the “mean”(or average), the number you would plug into your ballistic calculator for MV. This is the sum of all your velocities divided by the number of shots. ES is the extreme spread between the lowest and the highest velocity in a string of shots. SD is “standard deviation” which is a formula that calculates the distribution of the individual shots and produces a value that represents a confidence level where 95% of your fired shots will fall within a given range. The SD (as shown in the output in chronographs like the Magneto Speed, Oehler, etc.) can generally be multiplied by 4 to give you an approximation of the velocity spread where 95% of your shots will fall within this range. For example, an SD of 5 is approximately 20FPS, where you can expect 95% of your shots to fall within this velocity range. For my LR hunting to 1000 yards I shoot for an SD of 5-10, or an ES that’s less then 30FPS. This may sound high to some but it uses a sufficient sample of shots of shots(+20), and applies to the range of temperatures I expect to hunt. This value will keep my shots in the vital area of a whitetail/antelope out to 1000-1200 yards with my particular load, other factors considered. [/QUOTE]
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