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Long Range Hunting & Shooting
How much time and effort do you give a bullet, powder.
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<blockquote data-quote="nvschütze" data-source="post: 1688071" data-attributes="member: 110896"><p>To determine the Standard Deviation of a load, you'll need a chronograph. I shoot five rounds of the same load over mine, record the results and then consult a statistics website that does the calculation for me. I abysmally failed Stats in college, so I don't know how to calculate barely anything "statistical."</p><p></p><p>I go to the following website, input "5" for the number of rounds fired and input the five velocities. Click on "Calculate" and enjoy the results. The numbers you'll get back are expressed in scientific notation, but that's not a problem. You'll see the highest, lowest, mean (average), median (this is the number that most interests me) and Standard Deviation.</p><p></p><p>I am interested in the median because it's a better number than is the average. The median is the number that has an equal number of data points both above and below the "middle" of the data population. The average can be misleading. If you have nine velocities that are what you'd expect and one that's 1,000,000 fps, the average is going to be badly skewed upward. Of course, you're never going to see a muzzle velocity of a million fps, but you get the idea.</p><p></p><p>I fired five rounds over a chronograph; the velocities returned were 2715, 2682, 2704, 2721 and 2715. The mean is 2707, median is 2715, high is 2721, low is 2682. The Standard Deviation was calculated to be 15.5 fps; the Extreme Spread is 39. Using the median of 2715, the muzzle energy calculates to be 4092 foot-pounds. I get the KE from a ballistics calculation website, not from the link below. When your SD is very low, that means your muzzle velocities are very consistent. It means your bullets have a good chance of finding the same hole over and over again, lacking some sort of outside influencer like a gust of wind or a massive earthquake just as you fire the round. A high SD means your bullet velocities are wildly jumping up and down; you have very little consistency which manifests itself as large groups about which you'd not bother to write home.</p><p></p><p></p><p><a href="http://www.physics.csbsju.edu/stats/cstats_NROW_form.html" target="_blank">http://www.physics.csbsju.edu/stats/cstats_NROW_form.html</a></p></blockquote><p></p>
[QUOTE="nvschütze, post: 1688071, member: 110896"] To determine the Standard Deviation of a load, you'll need a chronograph. I shoot five rounds of the same load over mine, record the results and then consult a statistics website that does the calculation for me. I abysmally failed Stats in college, so I don't know how to calculate barely anything "statistical." I go to the following website, input "5" for the number of rounds fired and input the five velocities. Click on "Calculate" and enjoy the results. The numbers you'll get back are expressed in scientific notation, but that's not a problem. You'll see the highest, lowest, mean (average), median (this is the number that most interests me) and Standard Deviation. I am interested in the median because it's a better number than is the average. The median is the number that has an equal number of data points both above and below the "middle" of the data population. The average can be misleading. If you have nine velocities that are what you'd expect and one that's 1,000,000 fps, the average is going to be badly skewed upward. Of course, you're never going to see a muzzle velocity of a million fps, but you get the idea. I fired five rounds over a chronograph; the velocities returned were 2715, 2682, 2704, 2721 and 2715. The mean is 2707, median is 2715, high is 2721, low is 2682. The Standard Deviation was calculated to be 15.5 fps; the Extreme Spread is 39. Using the median of 2715, the muzzle energy calculates to be 4092 foot-pounds. I get the KE from a ballistics calculation website, not from the link below. When your SD is very low, that means your muzzle velocities are very consistent. It means your bullets have a good chance of finding the same hole over and over again, lacking some sort of outside influencer like a gust of wind or a massive earthquake just as you fire the round. A high SD means your bullet velocities are wildly jumping up and down; you have very little consistency which manifests itself as large groups about which you'd not bother to write home. [URL]http://www.physics.csbsju.edu/stats/cstats_NROW_form.html[/URL] [/QUOTE]
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