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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="groper" data-source="post: 474950" data-attributes="member: 12550"><p>G1 BC`s change DRAMATICALLY with velocity...</p><p></p><p>G7 BC`s change very little with velocity over the entire flight regime in which we are interested in, for the VLD bullets we are interested in.</p><p></p><p>BC`s dont change with environmental conditions. </p><p></p><p>BC`s dont change from one rifle to another. - caveat - the different rifling engraving marks on the bullet from different twist barrels and no of lands etc would effect the BC ever so slightly... however this effect is VERY small and would be extremely difficult to detect/measure/notice any difference - so its simply ignored and rightly so.</p><p></p><p>If you have a BC and velocity that is different from an accurately derived average BC by someone like Bryan Litz etc. AND you getting close to the mark with your doping, then you have adjusted your other variables such as velocity, bore ht, zero, environmentals etc. - in order to get there. These error-some adjustments you have now included in your trajectory calculation, means you WILL have significant trajectory errors at some point in your trajectory - it just might be much further down range than you normally shoot which is why you havnt noticed the problem... - which is WHY GETTING THE BC RIGHT IS SO IMPORTANT.</p><p></p><p>Which is why Bryan Litz has gone to all this trouble for us.</p><p></p><p>Which is why we should only use accurate BC`s users can trust in order to make an ethical LRH shot.</p><p></p><p>Which is why we should all be using the same BC, for the same bullet.</p><p></p><p>EDIT: I guarantee you will have a much better trajectory fit, over a larger portion of the trajectory, if you use a BC that bryan litz has published with your chronographed velocity (provided its working accuratey) You will then be able to find where your previous errors were, by changing the other variables such as bore ht, zero or environmentals etc in your ballistics calculator, to yeild grouping on the center x ring @ 1000yds.</p></blockquote><p></p>
[QUOTE="groper, post: 474950, member: 12550"] G1 BC`s change DRAMATICALLY with velocity... G7 BC`s change very little with velocity over the entire flight regime in which we are interested in, for the VLD bullets we are interested in. BC`s dont change with environmental conditions. BC`s dont change from one rifle to another. - caveat - the different rifling engraving marks on the bullet from different twist barrels and no of lands etc would effect the BC ever so slightly... however this effect is VERY small and would be extremely difficult to detect/measure/notice any difference - so its simply ignored and rightly so. If you have a BC and velocity that is different from an accurately derived average BC by someone like Bryan Litz etc. AND you getting close to the mark with your doping, then you have adjusted your other variables such as velocity, bore ht, zero, environmentals etc. - in order to get there. These error-some adjustments you have now included in your trajectory calculation, means you WILL have significant trajectory errors at some point in your trajectory - it just might be much further down range than you normally shoot which is why you havnt noticed the problem... - which is WHY GETTING THE BC RIGHT IS SO IMPORTANT. Which is why Bryan Litz has gone to all this trouble for us. Which is why we should only use accurate BC`s users can trust in order to make an ethical LRH shot. Which is why we should all be using the same BC, for the same bullet. EDIT: I guarantee you will have a much better trajectory fit, over a larger portion of the trajectory, if you use a BC that bryan litz has published with your chronographed velocity (provided its working accuratey) You will then be able to find where your previous errors were, by changing the other variables such as bore ht, zero or environmentals etc in your ballistics calculator, to yeild grouping on the center x ring @ 1000yds. [/QUOTE]
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Let's argue about BC's
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