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Rifles, Reloading, Optics, Equipment
Reloading
bullet seating accuracy
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<blockquote data-quote="MontanaRifleman" data-source="post: 841673" data-attributes="member: 11717"><p>If you're using COAL to determine how far off the lands you are, you wont be able to that accurately with cup and core bullets. Cup and core bullets have variation in their shape from bullet to bullet. If you get your calipers and measure the OALs of the bullets, you will see they vary in length. They also vary in bearing surfaces, ogive, etc. I just measured 10 230 Berger hybrids and their OAL differed by as much as .012. I put them nose first into a sized case (this is approximately where the ogive engages the lands) and measure from the case head to the base of the bullet and that varied up to .008 A bullet comparator does the same thing. </p><p></p><p>If you want to seat accurately and consistently "off the lands", then you need to use a bullet comparator and measure the seated ogive length of every round you seat and use a micrometer seating die to adjust for the differences. Some will also sort their bullets according to bearing surface as well. That's a lot of effort and I have never tried it and have been able to work up sub .5 MOA loads without doing either.</p><p></p><p>Hope that helps and Welcome to LRH!</p></blockquote><p></p>
[QUOTE="MontanaRifleman, post: 841673, member: 11717"] If you're using COAL to determine how far off the lands you are, you wont be able to that accurately with cup and core bullets. Cup and core bullets have variation in their shape from bullet to bullet. If you get your calipers and measure the OALs of the bullets, you will see they vary in length. They also vary in bearing surfaces, ogive, etc. I just measured 10 230 Berger hybrids and their OAL differed by as much as .012. I put them nose first into a sized case (this is approximately where the ogive engages the lands) and measure from the case head to the base of the bullet and that varied up to .008 A bullet comparator does the same thing. If you want to seat accurately and consistently "off the lands", then you need to use a bullet comparator and measure the seated ogive length of every round you seat and use a micrometer seating die to adjust for the differences. Some will also sort their bullets according to bearing surface as well. That's a lot of effort and I have never tried it and have been able to work up sub .5 MOA loads without doing either. Hope that helps and Welcome to LRH! [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
bullet seating accuracy
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