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Rifles, Reloading, Optics, Equipment
Reloading
Bullet bearing surface
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<blockquote data-quote="Jud96" data-source="post: 2868873" data-attributes="member: 69478"><p>I've been down the path of measuring bearing surface lengths accurately in order to determine what freebore I needed or if a given freebore would work with the desired bullet. I found the most accurate way to determine where a bullet will engage the lands in a typical 1.5 degree leade angle is by taking your calipers and setting them .002 below actual bullet diameter and slide the blades of the calipers down the bullet until they stop. Rotate the bullet or calipers to lightly etch it the bullet. Then measure from that mark to the bearing surface/boattail junction. This gets you within .020 of the actual number.</p><p></p><p>I found that Berger'a data can unintentionally be misleading because some bullets with a long tangent ogive, like their 6mm 108BT, appear to have a pretty short bearing surface. However, because of the long tapered ogive, that bullet will engage the lands sooner then a VLD bullet with an equal length published bearing surface. In short, you'll end up needed more freebore for the tangent ogive bullet vs. the VLD even though on paper the bearing surfaces may be very close. Sorry for the long winded response, but this is something I've struggled with in the past but feel I have a good way of determining the bearing surface length now.</p></blockquote><p></p>
[QUOTE="Jud96, post: 2868873, member: 69478"] I’ve been down the path of measuring bearing surface lengths accurately in order to determine what freebore I needed or if a given freebore would work with the desired bullet. I found the most accurate way to determine where a bullet will engage the lands in a typical 1.5 degree leade angle is by taking your calipers and setting them .002 below actual bullet diameter and slide the blades of the calipers down the bullet until they stop. Rotate the bullet or calipers to lightly etch it the bullet. Then measure from that mark to the bearing surface/boattail junction. This gets you within .020 of the actual number. I found that Berger’a data can unintentionally be misleading because some bullets with a long tangent ogive, like their 6mm 108BT, appear to have a pretty short bearing surface. However, because of the long tapered ogive, that bullet will engage the lands sooner then a VLD bullet with an equal length published bearing surface. In short, you’ll end up needed more freebore for the tangent ogive bullet vs. the VLD even though on paper the bearing surfaces may be very close. Sorry for the long winded response, but this is something I’ve struggled with in the past but feel I have a good way of determining the bearing surface length now. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Bullet bearing surface
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