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Rifles, Reloading, Optics, Equipment
Reloading
Bullet bearing surface question
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<blockquote data-quote="Mikecr" data-source="post: 231746" data-attributes="member: 1521"><p>No, No, it's just opposite..</p><p>.005" bearing variance could be significant to a tiny bullet on the edge of any distant performance(like a 20Vartarg at 300yds)(Hell I don't even know if a 20cal bullet has a bearing..), but amounts to absolutely NOTHING in a long range bullet..</p><p></p><p>And there are so many variables at 2kyd that it would always be a stretch to make any claims from the results. Think about it, what moa can anyone consistantly produce there? 1moa? 2moa? You think .005" of bearing variance would throw shots(in moa) so far at 100yds, or even 1000yds? </p><p>NO WAY</p><p>Well you could fire up QuickLoad, and JBM calcs, and see for yourself..</p><p></p><p>For example;</p><p>Say a 210Berger VLD has a bearing surface of .544</p><p>(.005" is nearly a 1% change)</p><p>If it's caused by reducing the nose length .005 with the same OAL, BC goes from ~.659 to ~.657</p><p>If it's caused by reducing boat tail .005 with same OAL, BC goes from ~.659 to ~.658</p><p>It's a mix, so BC might change anywhere from .001 to .002(or about 1% max)</p><p>At 1kyd the drop difference from 3kfpsMV & .002BC amounts to .3"</p><p>(thats .028moa)</p><p>I am sure your BC varies more than this -anyway-</p><p>I am also sure that any regular 1kyd shooter is working hard to cut 5 to 6" off their groups. So .3" there is probably not big on their 'things to conquer' list.</p><p></p><p>I'm not gonna lay out internal ballistics from QL, but a quick check indicates about 2fps increase from a .005 increase in bearing length with the same seating depth. I'd barely see it with 20ft screen spacing on my Oehler. But this would actually make up some of the loss in BC indicated above. </p><p>The barrel time change amounts to 1ns (Nanosecond).</p><p>If your tune requires this, you hurtin..</p><p>And there is always tungsten coating to negate all ballistic traces of this discussion.</p><p></p><p>Bearing surface checks can't hurt, unless you're doing it in place of things that really matter.</p><p>But that is what I believe is happening. I think people skip all the difficulties, condensing them down to bullet weight, or OAL, or bearing length.</p><p></p><p>Personally, I don't do it even with the best tools. Still working on that 5-6"......</p><p>[that's what she said]</p></blockquote><p></p>
[QUOTE="Mikecr, post: 231746, member: 1521"] No, No, it's just opposite.. .005" bearing variance could be significant to a tiny bullet on the edge of any distant performance(like a 20Vartarg at 300yds)(Hell I don't even know if a 20cal bullet has a bearing..), but amounts to absolutely NOTHING in a long range bullet.. And there are so many variables at 2kyd that it would always be a stretch to make any claims from the results. Think about it, what moa can anyone consistantly produce there? 1moa? 2moa? You think .005" of bearing variance would throw shots(in moa) so far at 100yds, or even 1000yds? NO WAY Well you could fire up QuickLoad, and JBM calcs, and see for yourself.. For example; Say a 210Berger VLD has a bearing surface of .544 (.005" is nearly a 1% change) If it's caused by reducing the nose length .005 with the same OAL, BC goes from ~.659 to ~.657 If it's caused by reducing boat tail .005 with same OAL, BC goes from ~.659 to ~.658 It's a mix, so BC might change anywhere from .001 to .002(or about 1% max) At 1kyd the drop difference from 3kfpsMV & .002BC amounts to .3" (thats .028moa) I am sure your BC varies more than this -anyway- I am also sure that any regular 1kyd shooter is working hard to cut 5 to 6" off their groups. So .3" there is probably not big on their 'things to conquer' list. I'm not gonna lay out internal ballistics from QL, but a quick check indicates about 2fps increase from a .005 increase in bearing length with the same seating depth. I'd barely see it with 20ft screen spacing on my Oehler. But this would actually make up some of the loss in BC indicated above. The barrel time change amounts to 1ns (Nanosecond). If your tune requires this, you hurtin.. And there is always tungsten coating to negate all ballistic traces of this discussion. Bearing surface checks can't hurt, unless you're doing it in place of things that really matter. But that is what I believe is happening. I think people skip all the difficulties, condensing them down to bullet weight, or OAL, or bearing length. Personally, I don't do it even with the best tools. Still working on that 5-6"...... [that's what she said] [/QUOTE]
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Bullet bearing surface question
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