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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
"Match" Chamber?
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<blockquote data-quote="Gcan" data-source="post: 1611561" data-attributes="member: 102867"><p>I believe you are on to it. I suspect if you did the same study for only long for caliber bullets (140-150 .264 and say 95 SMKs for 224 Valkyrie) you will find that velocity/diameter/rpm determine twist and there is a mathematical predictable relationship. I don't want to use a number without reading my notes but I believe 225,000 to 250,000 rpm is where I start. With the 224 everyone said 7 twist at first. Then 6.5 then 6.5 below 2600 and 7 above 2600 fps. We think in fps but its really rpms that determines stability and twist. I'm so sick of the 224 and flyers from bad non-concentric-necks and bad tempered brass from "—————" that I'm building a 22-250AI to shoot 95-100s. I should get 3100+ So by using rpm I get back to a 1:8 to shoot the same bullets a 224 needs a 6.5 to shoot at 2600-2700. </p><p></p><p>I think this is why some 264s need fast for caliber twists. Ex: a 6.5-284 is going to stabilize a 140 with a 1:9 or 1:10 twist where a 6.5CM or 260 Rem might need 1:9 to 1:8 or faster for same bullet. Put that same 140 in a 300UM case at near 4000fps and you might be at 1:12-1:14 (240,000 rpm) like a 22-250/50 grain. </p><p></p><p>I suspect that most of the 6.5s or rounds with hi twists that are anomalies will be slow fps for caliber with heavy bullets. </p><p></p><p>If that makes sense to anyone. </p><p>I'm not even sure I'm addressing your point.</p></blockquote><p></p>
[QUOTE="Gcan, post: 1611561, member: 102867"] I believe you are on to it. I suspect if you did the same study for only long for caliber bullets (140-150 .264 and say 95 SMKs for 224 Valkyrie) you will find that velocity/diameter/rpm determine twist and there is a mathematical predictable relationship. I don’t want to use a number without reading my notes but I believe 225,000 to 250,000 rpm is where I start. With the 224 everyone said 7 twist at first. Then 6.5 then 6.5 below 2600 and 7 above 2600 fps. We think in fps but its really rpms that determines stability and twist. I’m so sick of the 224 and flyers from bad non-concentric-necks and bad tempered brass from “—————“ that I’m building a 22-250AI to shoot 95-100s. I should get 3100+ So by using rpm I get back to a 1:8 to shoot the same bullets a 224 needs a 6.5 to shoot at 2600-2700. I think this is why some 264s need fast for caliber twists. Ex: a 6.5-284 is going to stabilize a 140 with a 1:9 or 1:10 twist where a 6.5CM or 260 Rem might need 1:9 to 1:8 or faster for same bullet. Put that same 140 in a 300UM case at near 4000fps and you might be at 1:12-1:14 (240,000 rpm) like a 22-250/50 grain. I suspect that most of the 6.5s or rounds with hi twists that are anomalies will be slow fps for caliber with heavy bullets. If that makes sense to anyone. I’m not even sure I’m addressing your point. [/QUOTE]
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"Match" Chamber?
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