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Rifles, Reloading, Optics, Equipment
Reloading
Consistent ES and SD
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<blockquote data-quote="SmokinCrow" data-source="post: 2747188" data-attributes="member: 62139"><p>Something to think about here is also how the statistics work. How many shots are you taking to calculate your sd/es? 5 shot groups aren't really enough to get true valid data. To get the most accurate information you need 30 shots for the sd to have sufficient data to be true and understand the bell curve of the sd. 66% of shots will fall within 1 sd of the average. 33% will fall within 2 sd of the mean. So you may not be seeing truth in any given group. That good sd/es that shoots bad could very well be one of the extremes that fall on the outliers and be in the far end of the 2nd sd of the average. Next several groups with same load could come in between 1/2-3/4 moa average. </p><p></p><p>Hornady has a podcast where they discuss the statistics and group sizes. Having taken stats in college I didn't put it together until I heard this podcast. I'd been chasing my tail trying to figure out why I always seemed to be chasing my tail with groups. I wasn't collecting enough data. I won't say the Hornady guys are the foremost experts and must be gospel truth. They don't say they are either. They say they are sharing what they have come to find in their testing and statistically makes sense. They say if something works for you great. They aren't trying to poopoo on other methods. They are sharing what they find with all their testing. Well worth a listen and very helpful. I asked them about sd/es and they said generally if there is an issue there neck tension is most common culprit. Also dispersion can increase with higher powder charge. Which makes sense when people talk about nodes and they find an upper node and a lower node with velocity and generally lower node tends to shoot better. </p><p></p><p>Good luck. Aim Small, Miss Small</p></blockquote><p></p>
[QUOTE="SmokinCrow, post: 2747188, member: 62139"] Something to think about here is also how the statistics work. How many shots are you taking to calculate your sd/es? 5 shot groups aren’t really enough to get true valid data. To get the most accurate information you need 30 shots for the sd to have sufficient data to be true and understand the bell curve of the sd. 66% of shots will fall within 1 sd of the average. 33% will fall within 2 sd of the mean. So you may not be seeing truth in any given group. That good sd/es that shoots bad could very well be one of the extremes that fall on the outliers and be in the far end of the 2nd sd of the average. Next several groups with same load could come in between 1/2-3/4 moa average. Hornady has a podcast where they discuss the statistics and group sizes. Having taken stats in college I didn’t put it together until I heard this podcast. I’d been chasing my tail trying to figure out why I always seemed to be chasing my tail with groups. I wasn’t collecting enough data. I won’t say the Hornady guys are the foremost experts and must be gospel truth. They don’t say they are either. They say they are sharing what they have come to find in their testing and statistically makes sense. They say if something works for you great. They aren’t trying to poopoo on other methods. They are sharing what they find with all their testing. Well worth a listen and very helpful. I asked them about sd/es and they said generally if there is an issue there neck tension is most common culprit. Also dispersion can increase with higher powder charge. Which makes sense when people talk about nodes and they find an upper node and a lower node with velocity and generally lower node tends to shoot better. Good luck. Aim Small, Miss Small [/QUOTE]
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