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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Let's argue about BC's
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<blockquote data-quote="rscott5028" data-source="post: 479828" data-attributes="member: 24624"><p>With all of the hair splitting, one thing I find lacking is adequate attention paid to statistics. </p><p> </p><p>We already know match bullets are not perfect and some use meplat trimmers at the detriment of BC in order to gain consistency. Who here is good enough to evaluate the meplat under a microscope and calculate the adjusted BC for the amount of deformation? Heck, I can see differences in meplat with my tired old eyes. Am I to assume that the ogive and boat tail are perfect for every bullet? (I think MC and BL already acknowledged differences among bullets and Lot #'s.) </p><p> </p><p>Hence, you can never know the "real/actual/precise" BC of an individual bullet until it is measured upon firing. Once fired, you can never repeat that test with the same bullet. So, we're really talking about using samples to estimate the BC of future bullets fired. </p><p> </p><p>While some advocate that the shape of a fired bullet has not changed because they retrieved the bullet and measured the dimensions. I challenge them to reload that same bullet and fire it again with the same measured BC. (And, I don't think they intended for that to be the case anyway.) </p><p> </p><p>I'm still eager to read the complete published works by BL, MC, Sierra and others. But, I sense they are simplifying things for us to talk about a % change in BC from this or that barrel. When we really should be concerned with statistical outliers. ...something they hinted at...</p><p></p><p>Statistically speaking, there are averages (mean), standard deviations, and distributions associated with these experiments. Their std dev is likely to be much less than mine due to the precision of their measuring and ability to control the variables. </p><p> </p><p>If I fire a few shots and measure a different BC, that's exactly what I've done and my observed data is irrefutable. Nonetheless, the source of the differences may not be accounted for as already discussed. And furthermore, the data alone does little to give a high degree of statistical credence, as in a 2 tailed T test with 95% or 99% confidence level, to my assertion that my BC is different from theirs. </p><p> </p><p>In fact, I may have to shoot a 3rd of a box of bullets (random samples from the whole Lot #) before I can statistically project the BC for that Lot. </p><p> </p><p>Fortunately, match bullets are pretty good quality and the std dev is likely to be very low (certainly better than my own shooting equipment and ability). As such, I'm pretty comfortable using BL's published BCs and I vow to do a better job identifying any discrepancies before I publicly flame the guy. </p><p> </p><p>BTW Bryan - You misspelled "very"</p><p></p><p>...should be "vary"</p><p> </p><p>But, we can debate that in another thread. ;-)</p><p> </p><p>-- richard</p></blockquote><p></p>
[QUOTE="rscott5028, post: 479828, member: 24624"] With all of the hair splitting, one thing I find lacking is adequate attention paid to statistics. We already know match bullets are not perfect and some use meplat trimmers at the detriment of BC in order to gain consistency. Who here is good enough to evaluate the meplat under a microscope and calculate the adjusted BC for the amount of deformation? Heck, I can see differences in meplat with my tired old eyes. Am I to assume that the ogive and boat tail are perfect for every bullet? (I think MC and BL already acknowledged differences among bullets and Lot #'s.) Hence, you can never know the "real/actual/precise" BC of an individual bullet until it is measured upon firing. Once fired, you can never repeat that test with the same bullet. So, we're really talking about using samples to estimate the BC of future bullets fired. While some advocate that the shape of a fired bullet has not changed because they retrieved the bullet and measured the dimensions. I challenge them to reload that same bullet and fire it again with the same measured BC. (And, I don't think they intended for that to be the case anyway.) I'm still eager to read the complete published works by BL, MC, Sierra and others. But, I sense they are simplifying things for us to talk about a % change in BC from this or that barrel. When we really should be concerned with statistical outliers. ...something they hinted at... Statistically speaking, there are averages (mean), standard deviations, and distributions associated with these experiments. Their std dev is likely to be much less than mine due to the precision of their measuring and ability to control the variables. If I fire a few shots and measure a different BC, that's exactly what I've done and my observed data is irrefutable. Nonetheless, the source of the differences may not be accounted for as already discussed. And furthermore, the data alone does little to give a high degree of statistical credence, as in a 2 tailed T test with 95% or 99% confidence level, to my assertion that my BC is different from theirs. In fact, I may have to shoot a 3rd of a box of bullets (random samples from the whole Lot #) before I can statistically project the BC for that Lot. Fortunately, match bullets are pretty good quality and the std dev is likely to be very low (certainly better than my own shooting equipment and ability). As such, I'm pretty comfortable using BL's published BCs and I vow to do a better job identifying any discrepancies before I publicly flame the guy. BTW Bryan - You misspelled "very" ...should be "vary" But, we can debate that in another thread. ;-) -- richard [/QUOTE]
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