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Rifles, Reloading, Optics, Equipment
Reloading
Trying to understand sd and es in load development
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<blockquote data-quote="RegionRat" data-source="post: 1573179" data-attributes="member: 57231"><p>An SD is a way of describing the width of a normal distribution. Once you have an average and an SD, you should be able to predict the full width of the tails of that normal distribution, and we call that full width the ES. </p><p></p><p>If the process is normal, the relationship between the SD and the ES is a factor of six. So if you know the average, you can estimate the high by adding 3xSD and the low by subtracting 3xSD. The difference between them is the ES. So, if for example we have something with an SD of 1 and an average of 10, we can estimate the high will be 13 and the low will be 7, with an ES of 6.</p><p></p><p>When we shoot much past about 600 yards, the SD begins to matter because it contributes to vertical dispersion just on the basis of the difference in trajectory between the fastest and slowest shots in the group. However, you only had a 4 shot sample...</p><p></p><p>It takes more than 7 samples to start to really see what the SD will become when we are lucky, and something like 15 shots when we are not so lucky.</p><p></p><p>So, you don't have enough samples to judge the SD of the loads, but if the SD with 4 samples is large, it will only get bigger with more samples anyway.</p><p></p><p>It is sometimes possible to see a load with a higher SD and ES give a tighter group than a load with a tighter statistic. This happens for two reasons, the sample size is too small and those stats are not true, and because the shooting is done at short range so the ES hasn't shown up in the groups yet. If you are shooting less than 600 yards, the ES will just being to show.</p><p></p><p>Keep working your load development. If you find a stable speed node, you can run an development for seating depth and see what happens. If you find a good group, then take that load out to your maximum distance and see if it is good enough. YMMV</p></blockquote><p></p>
[QUOTE="RegionRat, post: 1573179, member: 57231"] An SD is a way of describing the width of a normal distribution. Once you have an average and an SD, you should be able to predict the full width of the tails of that normal distribution, and we call that full width the ES. If the process is normal, the relationship between the SD and the ES is a factor of six. So if you know the average, you can estimate the high by adding 3xSD and the low by subtracting 3xSD. The difference between them is the ES. So, if for example we have something with an SD of 1 and an average of 10, we can estimate the high will be 13 and the low will be 7, with an ES of 6. When we shoot much past about 600 yards, the SD begins to matter because it contributes to vertical dispersion just on the basis of the difference in trajectory between the fastest and slowest shots in the group. However, you only had a 4 shot sample... It takes more than 7 samples to start to really see what the SD will become when we are lucky, and something like 15 shots when we are not so lucky. So, you don’t have enough samples to judge the SD of the loads, but if the SD with 4 samples is large, it will only get bigger with more samples anyway. It is sometimes possible to see a load with a higher SD and ES give a tighter group than a load with a tighter statistic. This happens for two reasons, the sample size is too small and those stats are not true, and because the shooting is done at short range so the ES hasn’t shown up in the groups yet. If you are shooting less than 600 yards, the ES will just being to show. Keep working your load development. If you find a stable speed node, you can run an development for seating depth and see what happens. If you find a good group, then take that load out to your maximum distance and see if it is good enough. YMMV [/QUOTE]
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Trying to understand sd and es in load development
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