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Rifles, Reloading, Optics, Equipment
Reloading
5 or 3 shot group when determining ES/SD???
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<blockquote data-quote="Bart B" data-source="post: 626040" data-attributes="member: 5302"><p>There's one other variable that'll cause errors between measured velocity and actual velocity. It's us humans who don't hold the rifle against our shoulder with the same force/pressure for each shot. I've seen as much as 50 fps difference between two people chronographing the same load in the same rifle. And both of us could easily cause a 20 fps error by holding the rifle against our shoulder a little bit different for each shot. I could vary average velocity as much as 40 fps without much effort.</p><p></p><p>So I'm convinced that shooting a centerfire rifle off the shoulder as it rests atop something on a bench ain't accurate to less than 5 fps, maybe even 10 fps for some folks. Results from rifles fired from a machine rest show much less extreme spread and lower standard deviations. No wonder SAAMI uses hard-mounted universal receivers and test barrels to measure velocity data to eliminate as many variables as possible.</p><p></p><p>The good news is our handloads probably produce smaller velocity spreads than we typically get with chronographs' data from bench-fired rifles. The bad news is we gotta shoot more rounds to get a more accurate data for both SD and ES</p></blockquote><p></p>
[QUOTE="Bart B, post: 626040, member: 5302"] There's one other variable that'll cause errors between measured velocity and actual velocity. It's us humans who don't hold the rifle against our shoulder with the same force/pressure for each shot. I've seen as much as 50 fps difference between two people chronographing the same load in the same rifle. And both of us could easily cause a 20 fps error by holding the rifle against our shoulder a little bit different for each shot. I could vary average velocity as much as 40 fps without much effort. So I'm convinced that shooting a centerfire rifle off the shoulder as it rests atop something on a bench ain't accurate to less than 5 fps, maybe even 10 fps for some folks. Results from rifles fired from a machine rest show much less extreme spread and lower standard deviations. No wonder SAAMI uses hard-mounted universal receivers and test barrels to measure velocity data to eliminate as many variables as possible. The good news is our handloads probably produce smaller velocity spreads than we typically get with chronographs' data from bench-fired rifles. The bad news is we gotta shoot more rounds to get a more accurate data for both SD and ES [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
5 or 3 shot group when determining ES/SD???
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