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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
6.5-06 1-10 twist with 130 Bergers
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<blockquote data-quote="Darkker" data-source="post: 1072838" data-attributes="member: 81406"><p>Few things to consider, in the answer you seek.</p><p>First is actual twist rate. It is very normal for a mfg to have up to 1/2 faster/slower twist than stated. So the actual twist will affect the reality.</p><p>The second thing is barrel smoothness. This is the bit about voodoo that really can change things. A rough fast twist is almost worse than a smooth slow one. </p><p>Last is "how" unstable is it? Provided you input all the correct variables in the calc, the air changes will help or hurt. If you are just outside stable (Green, yellow, red are the outcomes) then the first two items I said are where you can see the effect. So for an example, with the velocities my group runs; a 9-twisty 223 isn't exactly "ideal" with the 77gr SMK. The reality is only one rifle struggles to get them stable. </p><p>The last bit is about decay. Since my 77gr's are yellow, they don't group amazingly up close. But velocity decay happens very quickly, whereas rotational decay is very slow. So as the bullet slows going down range, it's relative RPM(relative to velocity) will increase; adding dynamic stability to the projectile.</p></blockquote><p></p>
[QUOTE="Darkker, post: 1072838, member: 81406"] Few things to consider, in the answer you seek. First is actual twist rate. It is very normal for a mfg to have up to 1/2 faster/slower twist than stated. So the actual twist will affect the reality. The second thing is barrel smoothness. This is the bit about voodoo that really can change things. A rough fast twist is almost worse than a smooth slow one. Last is "how" unstable is it? Provided you input all the correct variables in the calc, the air changes will help or hurt. If you are just outside stable (Green, yellow, red are the outcomes) then the first two items I said are where you can see the effect. So for an example, with the velocities my group runs; a 9-twisty 223 isn't exactly "ideal" with the 77gr SMK. The reality is only one rifle struggles to get them stable. The last bit is about decay. Since my 77gr's are yellow, they don't group amazingly up close. But velocity decay happens very quickly, whereas rotational decay is very slow. So as the bullet slows going down range, it's relative RPM(relative to velocity) will increase; adding dynamic stability to the projectile. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
6.5-06 1-10 twist with 130 Bergers
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