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Rifles, Reloading, Optics, Equipment
Reloading
Standard Deviation
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<blockquote data-quote="Hugnot" data-source="post: 2639609" data-attributes="member: 115658"><p>SD - Standard Deviation:</p><p></p><p>"In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range."</p><p></p><p>I use SD as a general indicator for ammo consistency. This assumes a bell-shaped curve (normal distribution) with low to high values and a mean midway.</p><p></p><p>Imagine, shooting a 5 shot string, producing a SD of less than 5 fps, but round #6, if tested, would produce a SD of 25. Shooter confidence for making that 1,000-yard would go from nice at a 5 round SD, to terrible at a 6 round SD.</p><p></p><p>Playing around with this stuff will also provide average low and high range values at a certain % interval or "confidence", like 2 1/2 % at each end or 95% confidence. This will provide low & high averages. I produce moderate amount of ammo lots, like 250-500 rounds per lot, and try to get maximum consistency and like to see both tail ends of the curve show minimum differences.</p><p></p><p>Shooting deers & such at 1,000 yards, is way beyond my ability. I usually rely on 2 sighter shots to get within 4 inches of target center at 1,000 and can't do sighter shots for shooting deers. Having nice ammo with a low mean velocity spread at each tail end assures an elevated hit rate on pop can size rodents at ranges like 450 - 600 yards provided the bullets are pointy and have zippy velocities.</p></blockquote><p></p>
[QUOTE="Hugnot, post: 2639609, member: 115658"] SD - Standard Deviation: "In statistics, the standard deviation is a measure of the amount of variation or dispersion of a set of values. A low standard deviation indicates that the values tend to be close to the mean (also called the expected value) of the set, while a high standard deviation indicates that the values are spread out over a wider range." I use SD as a general indicator for ammo consistency. This assumes a bell-shaped curve (normal distribution) with low to high values and a mean midway. Imagine, shooting a 5 shot string, producing a SD of less than 5 fps, but round #6, if tested, would produce a SD of 25. Shooter confidence for making that 1,000-yard would go from nice at a 5 round SD, to terrible at a 6 round SD. Playing around with this stuff will also provide average low and high range values at a certain % interval or "confidence", like 2 1/2 % at each end or 95% confidence. This will provide low & high averages. I produce moderate amount of ammo lots, like 250-500 rounds per lot, and try to get maximum consistency and like to see both tail ends of the curve show minimum differences. Shooting deers & such at 1,000 yards, is way beyond my ability. I usually rely on 2 sighter shots to get within 4 inches of target center at 1,000 and can't do sighter shots for shooting deers. Having nice ammo with a low mean velocity spread at each tail end assures an elevated hit rate on pop can size rodents at ranges like 450 - 600 yards provided the bullets are pointy and have zippy velocities. [/QUOTE]
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