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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Berger Twist Rate Stability Calculator (need help)
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<blockquote data-quote="Hugnot" data-source="post: 2024452" data-attributes="member: 115658"><p>I have found the Miller Sg estimator to be on the conservative side. I have got extremely good accuracy with Miller Sg's under 1.5 but conditions were warm at 3000 ft. elevation. On the other hand my 8 twist .243 shooting the 87 VMax at 3250 has a Miller Sg of 2.89 and is very accurate having prairie dog hits at 400 - 85*, 3000 ft. elevation; no jacket separation but what would happen with a 7 twist at 3400 fps? 29.92 (H83) is sort of a standard but at higher elevations it would be less causing the Sg estimate to increase.</p><p>[ATTACH=full]226042[/ATTACH]</p><p></p><p>The calculations for the 87 VMax, are shown on the top bar. No great mystery - just simple math. The 87 VMax data/values are in column "H". Numbers found in column H, rows 76 to 83 were plugged into the equation in the top bar. The resultant Sg appears in column H, row 85. This stuff would be lots easier using FORTRAN or C. Just numbers used to come up with a estimated Sg. This is a real good tool for buying bullets & new barrels. Will my new 8 twist, 6mm-06 blow up 75 VMax's? I really like the 87 VMax out of a 10 twist @ 3450 +-, 6mm AI. If in doubt go for a faster twist.</p><p></p><p>Additional info:</p><p></p><p>[URL unfurl="true"]https://arxiv.org/ftp/arxiv/papers/1410/1410.5340.pdf[/URL]</p></blockquote><p></p>
[QUOTE="Hugnot, post: 2024452, member: 115658"] I have found the Miller Sg estimator to be on the conservative side. I have got extremely good accuracy with Miller Sg's under 1.5 but conditions were warm at 3000 ft. elevation. On the other hand my 8 twist .243 shooting the 87 VMax at 3250 has a Miller Sg of 2.89 and is very accurate having prairie dog hits at 400 - 85*, 3000 ft. elevation; no jacket separation but what would happen with a 7 twist at 3400 fps? 29.92 (H83) is sort of a standard but at higher elevations it would be less causing the Sg estimate to increase. [ATTACH type="full" alt="Screenshot (63).png"]226042[/ATTACH] The calculations for the 87 VMax, are shown on the top bar. No great mystery - just simple math. The 87 VMax data/values are in column "H". Numbers found in column H, rows 76 to 83 were plugged into the equation in the top bar. The resultant Sg appears in column H, row 85. This stuff would be lots easier using FORTRAN or C. Just numbers used to come up with a estimated Sg. This is a real good tool for buying bullets & new barrels. Will my new 8 twist, 6mm-06 blow up 75 VMax's? I really like the 87 VMax out of a 10 twist @ 3450 +-, 6mm AI. If in doubt go for a faster twist. Additional info: [URL unfurl="true"]https://arxiv.org/ftp/arxiv/papers/1410/1410.5340.pdf[/URL] [/QUOTE]
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Berger Twist Rate Stability Calculator (need help)
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