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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
6mm Creedmoor barrel twist?
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<blockquote data-quote="Hugnot" data-source="post: 3095250" data-attributes="member: 115658"><p>I don't see much difference between the 7 or 7.5 twist except a 7 twist might be excessive for the plastic tipped Hornady 108 ELDM. On a warm day at higher elevations with lower air pressure Sg numbers will be much more than 2.0 with the 108 Hornady ELDM. Miller & other bullet wizards suggest optimum accuracy would be obtained at Sg values between 1.4 & 2.0.</p><p></p><p>[URL unfurl="true"]https://arxiv.org/ftp/arxiv/papers/1410/1410.5340.pdf[/URL]</p><p></p><p>The Miller process is accepted by Berger & other bullet makers. Berger uses elevation in their stability calculations and I would guess elevations in Indiana would not exceed 1,500 ft. Higher elevations result in lower pressures & higher Sg values.</p><p></p><p>Some Sg values using a 7 twist. I can get an honest 3.000 fps from my 8 twist, 24 inch, 6mm CM using the 105 Barnes Match Burner ( $0.30 each when bought by 500 bullet lots) & 40.5 grains of H4350. I use small rifle primers in my 6mm CM. At times I shoot at elevations over 5,000 ft. at temps over 80 F.</p><p></p><p>[ATTACH]567848[/ATTACH]</p></blockquote><p></p>
[QUOTE="Hugnot, post: 3095250, member: 115658"] I don't see much difference between the 7 or 7.5 twist except a 7 twist might be excessive for the plastic tipped Hornady 108 ELDM. On a warm day at higher elevations with lower air pressure Sg numbers will be much more than 2.0 with the 108 Hornady ELDM. Miller & other bullet wizards suggest optimum accuracy would be obtained at Sg values between 1.4 & 2.0. [URL unfurl="true"]https://arxiv.org/ftp/arxiv/papers/1410/1410.5340.pdf[/URL] The Miller process is accepted by Berger & other bullet makers. Berger uses elevation in their stability calculations and I would guess elevations in Indiana would not exceed 1,500 ft. Higher elevations result in lower pressures & higher Sg values. Some Sg values using a 7 twist. I can get an honest 3.000 fps from my 8 twist, 24 inch, 6mm CM using the 105 Barnes Match Burner ( $0.30 each when bought by 500 bullet lots) & 40.5 grains of H4350. I use small rifle primers in my 6mm CM. At times I shoot at elevations over 5,000 ft. at temps over 80 F. [ATTACH alt="Screenshot (902).png"]567848[/ATTACH] [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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6mm Creedmoor barrel twist?
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