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Long Range Hunting & Shooting
Anyone ever use a Meplat Trimmer?
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<blockquote data-quote="Mikecr" data-source="post: 2703826" data-attributes="member: 1521"><p>For the challenge of it, I loaded a 26cal 140 VLD into some bullet design stuff to see what affects meplat trimming has to BC.</p><p>Parameters for the bullet, with each changing for a <u><strong>10thou</strong></u> trim:</p><p><u><strong>Initial,</strong></u> <u><strong>BC,</strong></u> <u><strong>Trimmed</strong></u>, <u><strong>BC</strong></u>, <u><strong>change</strong></u></p><p>OAL 1.412" 0.609 1.402" 0.609 0.0%</p><p>WEIGHT 140gr 0.609 139.1gr 0.605 0.66%</p><p>NL 0.740" 0.609 0.730" 0.602 0.50%</p><p>MD 0.062" 0.609 0.067" 0.582 3.32%</p><p> 4.43% Overall</p><p></p><p>As predicted, MEPLAT DIAMETER has by far the largest affect to BC with trimming.</p><p>OAL, NL, and WEIGHT, from trimming, is insignificant.</p><p>Given this, meplats should not be trimmed for same OAL, NL, or WEIGHT, but for same DIAMETERS.</p><p>We don't have a good way to do that. We don't even have a good way to measure meplat diameters.</p><p></p><p>If you're gonna do it though, I suggest pointing first, before trimming.</p><p>With this, meplat diameter variance from trimming should be affected least, given meplats that are smaller to begin.</p><p>And you don't want an abrupt ogive radius change with your pointing. The Hoover system is best at avoiding this.</p><p></p><p>Also keep in mind that BC goes up with smaller meplats, but then begins to drop with meplats that are too small.</p><p>From 0.012" or less, BC undergoes a relatively mild decreasing. So a good trim-to meplat diameter of pointed bullets would be ~0.015" or greater. Don't sharpen tips, but shape for a slight rounding radius at edges.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 2703826, member: 1521"] For the challenge of it, I loaded a 26cal 140 VLD into some bullet design stuff to see what affects meplat trimming has to BC. Parameters for the bullet, with each changing for a [U][B]10thou[/B][/U] trim: [U][B]Initial,[/B][/U] [U][B]BC,[/B][/U] [U][B]Trimmed[/B][/U], [U][B]BC[/B][/U], [U][B]change[/B][/U] OAL 1.412" 0.609 1.402" 0.609 0.0% WEIGHT 140gr 0.609 139.1gr 0.605 0.66% NL 0.740" 0.609 0.730" 0.602 0.50% MD 0.062" 0.609 0.067" 0.582 3.32% 4.43% Overall As predicted, MEPLAT DIAMETER has by far the largest affect to BC with trimming. OAL, NL, and WEIGHT, from trimming, is insignificant. Given this, meplats should not be trimmed for same OAL, NL, or WEIGHT, but for same DIAMETERS. We don't have a good way to do that. We don't even have a good way to measure meplat diameters. If you're gonna do it though, I suggest pointing first, before trimming. With this, meplat diameter variance from trimming should be affected least, given meplats that are smaller to begin. And you don't want an abrupt ogive radius change with your pointing. The Hoover system is best at avoiding this. Also keep in mind that BC goes up with smaller meplats, but then begins to drop with meplats that are too small. From 0.012" or less, BC undergoes a relatively mild decreasing. So a good trim-to meplat diameter of pointed bullets would be ~0.015" or greater. Don't sharpen tips, but shape for a slight rounding radius at edges. [/QUOTE]
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Anyone ever use a Meplat Trimmer?
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