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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
7mm Berger 180 Hybrid twist rate help
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<blockquote data-quote="groper" data-source="post: 474082" data-attributes="member: 12550"><p>Well so long as your stability factor is above 1.1 then the bullets will fly... sometimes however, with very low stability factors close to 1.0, many people have observed poor accuracy just prior to the bullets tumbling. I dont entirely understand why this happens, as according to much research (including bryan litz`s publications) the larger epicyclic yaw angles cannot induce anywhere near this much dispersion, not from just the large yaw angle alone.</p><p></p><p>By far the biggest influence on dispersion, seems to be projectile muzzle jump - which contains many elements within it, including bore axis alignment and in bore balloting, projectile concentricity, projectile center of gravity axial alignment is a large factor, barrel vibration/movement and more...</p><p></p><p>Accuracy and projectile stability are 2 very different things, and although sometimes they seem to go hand in hand, it may not be for reasons relating to each other...</p><p></p><p>As far a stability goes, the industry standard seems to beleive the ideal stability factor to be 1.49... i think anything above 1.2 can work fine depending on your individual rifle system, just dont expect it to work when the weather turns and gets very cold etc. For example, the .375 cheytac system using the 350gr Lost river copper alloy solids from their 1:11.5 barrel has a stability factor of ~1.2 in a std atmosphere at sea level...</p></blockquote><p></p>
[QUOTE="groper, post: 474082, member: 12550"] Well so long as your stability factor is above 1.1 then the bullets will fly... sometimes however, with very low stability factors close to 1.0, many people have observed poor accuracy just prior to the bullets tumbling. I dont entirely understand why this happens, as according to much research (including bryan litz`s publications) the larger epicyclic yaw angles cannot induce anywhere near this much dispersion, not from just the large yaw angle alone. By far the biggest influence on dispersion, seems to be projectile muzzle jump - which contains many elements within it, including bore axis alignment and in bore balloting, projectile concentricity, projectile center of gravity axial alignment is a large factor, barrel vibration/movement and more... Accuracy and projectile stability are 2 very different things, and although sometimes they seem to go hand in hand, it may not be for reasons relating to each other... As far a stability goes, the industry standard seems to beleive the ideal stability factor to be 1.49... i think anything above 1.2 can work fine depending on your individual rifle system, just dont expect it to work when the weather turns and gets very cold etc. For example, the .375 cheytac system using the 350gr Lost river copper alloy solids from their 1:11.5 barrel has a stability factor of ~1.2 in a std atmosphere at sea level... [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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7mm Berger 180 Hybrid twist rate help
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