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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Es/sd
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<blockquote data-quote="MontanaRifleman" data-source="post: 373304" data-attributes="member: 11717"><p>ES = extreme spread = the spread between the highest and lowest velocity in a group.</p><p> </p><p>SD = standard deviation.</p><p> </p><p>A defintion of SD from wiki...</p><p> </p><p></p><p> </p><p> </p><p>These numbers are derived by shooting through a chrony that measures bullet velocity. I personally dont put much stock in them because chrony's are not precision instrumnets. I have seen a lot of inconsistancies with my chronys (I have two) When I shoot them back to back their velocites will vary anywhere from 5-60 fps.</p><p> </p><p>If you shoot a 5 shot string and get the following velocities...</p><p> </p><p>3056, 3067, 3094, 3094 and 3069, Your ES is 3094 - 3056 = 38</p><p> </p><p>However, the odds are very lilkely that your actual ES is smaller.</p><p> </p><p>The reason being, Your chrony is accurate to plus or minus "x" fps. The shot that measured 3056 might actually be 3070 and the shot that measured 3094 might actually be 3080. For this reason, I put almost no stock in chrony measured ES's. I use actual group results to determine my best loads.</p><p> </p><p>A good experiment to try is go out and shoot a 5 shot string, record the results and repeat the next day under similar light conditions (light conditions will affect readings) I can pretty much guarantee you that you will get different results.</p></blockquote><p></p>
[QUOTE="MontanaRifleman, post: 373304, member: 11717"] ES = extreme spread = the spread between the highest and lowest velocity in a group. SD = standard deviation. A defintion of SD from wiki... These numbers are derived by shooting through a chrony that measures bullet velocity. I personally dont put much stock in them because chrony's are not precision instrumnets. I have seen a lot of inconsistancies with my chronys (I have two) When I shoot them back to back their velocites will vary anywhere from 5-60 fps. If you shoot a 5 shot string and get the following velocities... 3056, 3067, 3094, 3094 and 3069, Your ES is 3094 - 3056 = 38 However, the odds are very lilkely that your actual ES is smaller. The reason being, Your chrony is accurate to plus or minus "x" fps. The shot that measured 3056 might actually be 3070 and the shot that measured 3094 might actually be 3080. For this reason, I put almost no stock in chrony measured ES's. I use actual group results to determine my best loads. A good experiment to try is go out and shoot a 5 shot string, record the results and repeat the next day under similar light conditions (light conditions will affect readings) I can pretty much guarantee you that you will get different results. [/QUOTE]
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