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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
New Beast from Allen Precision Shooting!!!
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<blockquote data-quote="Varminator 911" data-source="post: 1613814" data-attributes="member: 9705"><p>Or keep all 700 gn and make the bullet an inch longer. That would require a faster twist but right now he's only talking a 12 twist barrel. There's lots of room for a longer bullet. When adding weight it doesn't all need to be longer bearing surface and a heavier bullet.</p><p></p><p></p><p></p><p>I'm no genius about bullets. But my understanding is that BC = sectional density divided by form factor. So at the same form factor, BC is proportional to bullet weight. I don't see that as a lot more effect than expected. Increasing bullet weight has a cost, velocity. Improving form factor has no cost assuming the bullet is accurate and performs as needed. By reducing, improving, form factor you can maintain velocity and increase BC. That gives improved exterior ballistics.</p><p></p><p>The advantage of the big calipers over the small is that it takes a lot less twist to stabilize bullets of equal SD at the big calipers as compared to small. You can't get much BC with monomentals in small calipers because they can't spin up a bullet with much SD. </p><p></p><p>A 700 gn 458 bullet has SD of 0.476. You can stabilize the example above at 12 twist. A 6.5 mm bullet with SD of 0.476 would weigh 233 gn. It better be flat on both ends to stabilize with a 7 twist.</p><p></p><p><a href="https://bergerbullets.com/form-factors-a-useful-analysis-tool/" target="_blank">https://bergerbullets.com/form-factors-a-useful-analysis-tool/</a></p></blockquote><p></p>
[QUOTE="Varminator 911, post: 1613814, member: 9705"] Or keep all 700 gn and make the bullet an inch longer. That would require a faster twist but right now he's only talking a 12 twist barrel. There's lots of room for a longer bullet. When adding weight it doesn't all need to be longer bearing surface and a heavier bullet. I'm no genius about bullets. But my understanding is that BC = sectional density divided by form factor. So at the same form factor, BC is proportional to bullet weight. I don't see that as a lot more effect than expected. Increasing bullet weight has a cost, velocity. Improving form factor has no cost assuming the bullet is accurate and performs as needed. By reducing, improving, form factor you can maintain velocity and increase BC. That gives improved exterior ballistics. The advantage of the big calipers over the small is that it takes a lot less twist to stabilize bullets of equal SD at the big calipers as compared to small. You can't get much BC with monomentals in small calipers because they can't spin up a bullet with much SD. A 700 gn 458 bullet has SD of 0.476. You can stabilize the example above at 12 twist. A 6.5 mm bullet with SD of 0.476 would weigh 233 gn. It better be flat on both ends to stabilize with a 7 twist. [URL]https://bergerbullets.com/form-factors-a-useful-analysis-tool/[/URL] [/QUOTE]
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New Beast from Allen Precision Shooting!!!
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