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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Twist vs Bullet Weight Question
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<blockquote data-quote="Calvin45" data-source="post: 2938012" data-attributes="member: 109862"><p>Though I am working up a load for my 300 win 10 twist with that same 200 smk haha. Talked to the folks at Sierra via email. They think I'll be fine. The 1:9 twist is to ensure full stability at .308 velocity at sea level. 1:10 at .300 win velocity even at my modest 1100 feet elevation should have zero issues they tell me. </p><p></p><p>That's a whole other can of worms too haha! </p><p></p><p>Air Temperature, humidity, elevation, and muzzle velocity all play into whether a given twist rate is sufficient to stabilize a given projectile. </p><p></p><p>Hot air is less dense than cold, humid air is less dense than dry (yes, less: it feels thicker to us, but water vapour is lighter than air), the air is thinner the higher up you go, and the slower you run the bullet through the barrel to start with the lower it's RPMs are and this can become evidently problematic as distance increases (bullets don't really lose any rotational velocity in flight, not enough to matter: even if it's slowed down a lot in terms of horizontal velocity, it's still spinning about as fast as it was when it left the barrel. As velocity drops, higher rpms are a good thing usually.</p></blockquote><p></p>
[QUOTE="Calvin45, post: 2938012, member: 109862"] Though I am working up a load for my 300 win 10 twist with that same 200 smk haha. Talked to the folks at Sierra via email. They think I’ll be fine. The 1:9 twist is to ensure full stability at .308 velocity at sea level. 1:10 at .300 win velocity even at my modest 1100 feet elevation should have zero issues they tell me. That’s a whole other can of worms too haha! Air Temperature, humidity, elevation, and muzzle velocity all play into whether a given twist rate is sufficient to stabilize a given projectile. Hot air is less dense than cold, humid air is less dense than dry (yes, less: it feels thicker to us, but water vapour is lighter than air), the air is thinner the higher up you go, and the slower you run the bullet through the barrel to start with the lower it’s RPMs are and this can become evidently problematic as distance increases (bullets don’t really lose any rotational velocity in flight, not enough to matter: even if it’s slowed down a lot in terms of horizontal velocity, it’s still spinning about as fast as it was when it left the barrel. As velocity drops, higher rpms are a good thing usually. [/QUOTE]
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Twist vs Bullet Weight Question
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