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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Berger Prep for Terminal Performance
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<blockquote data-quote="CONatureBoy" data-source="post: 2741309" data-attributes="member: 118769"><p>I just got my 6.5mm trimmer today. I trimmed a box of the 156-grain EOLs I previously drilled to 0.0465". I then measured bullet overall length for a random sample of 30 drilled and trimmed bullets, and also for a random sample of 30 factory bullets. Here are the summary statistics:</p><p></p><p>Factory</p><p>Min. Length 1.507</p><p>Max. Length 1.516</p><p>Mean Length 1.512</p><p>ES 0.009</p><p>SD 0.002</p><p></p><p>Drilled/Trimmed</p><p>Min. Length 1.494</p><p>Max. Length 1.498</p><p>Mean Length 1.495</p><p>ES 0.004</p><p>SD 0.001</p><p></p><p>Here's the F test comparing the two variances (squares of the SDs), concluding that the drilled/trimmed SD is indeed significantly smaller than the factory SD:</p><p></p><p>[ATTACH=full]437445[/ATTACH]</p><p></p><p>Here are the length histograms:</p><p></p><p>[ATTACH=full]437373[/ATTACH]</p><p>So drilling and trimming (the way I do it) reduces the variation in length by half. You can judge concentricity of the drilling from this picture (drilled in front, factory in back):</p><p></p><p>[ATTACH=full]437374[/ATTACH]</p><p>I'll shoot a 10-shot ladder this weekend (RL-33 from 74.2 to 75.1 grains, in 0.1-grain increments), and report results here. The results above suggest target shooters who trim meplats for accuracy are onto something.</p></blockquote><p></p>
[QUOTE="CONatureBoy, post: 2741309, member: 118769"] I just got my 6.5mm trimmer today. I trimmed a box of the 156-grain EOLs I previously drilled to 0.0465". I then measured bullet overall length for a random sample of 30 drilled and trimmed bullets, and also for a random sample of 30 factory bullets. Here are the summary statistics: Factory Min. Length 1.507 Max. Length 1.516 Mean Length 1.512 ES 0.009 SD 0.002 Drilled/Trimmed Min. Length 1.494 Max. Length 1.498 Mean Length 1.495 ES 0.004 SD 0.001 Here's the F test comparing the two variances (squares of the SDs), concluding that the drilled/trimmed SD is indeed significantly smaller than the factory SD: [ATTACH type="full" alt="1675997288276.png"]437445[/ATTACH] Here are the length histograms: [ATTACH type="full" alt="1675985702945.png"]437373[/ATTACH] So drilling and trimming (the way I do it) reduces the variation in length by half. You can judge concentricity of the drilling from this picture (drilled in front, factory in back): [ATTACH type="full" alt="1675985901531.png"]437374[/ATTACH] I'll shoot a 10-shot ladder this weekend (RL-33 from 74.2 to 75.1 grains, in 0.1-grain increments), and report results here. The results above suggest target shooters who trim meplats for accuracy are onto something. [/QUOTE]
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Berger Prep for Terminal Performance
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