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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Future H.A.T B.C. Test shoot
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<blockquote data-quote="noel carlson" data-source="post: 358985" data-attributes="member: 16138"><p>Mark,</p><p> </p><p>"... Not sure if that remains the same going to a different bore size?"... I missed your appendix last night, and it does bring up some interesting issues.</p><p> </p><p>Bore size, and twist-rate are essentially scalable. In 5.5+ caliber projectiles there is another factor that comes into play which has an effect that must be taken into account.</p><p> </p><p>The ZA relies heavily on tail geometry to maintain high velocity stability. In order for the tail design to be effective hovever, laminar flow needs to be preserved across it's surface. The Reynold's effect states, in essence, that an object of "A" diameter, at "B" velocity, will produce the same laminar/turbulence flow properties as an identical object of (1/2) "A" diameter, and (2) "B" velocity. </p><p> </p><p>To simulate a 50 caliber projectile at 2,500 fps, I would need to run a 25 caliber model at 5,000 fps. Bryan might want to weigh in here, but the practical result is that a projectile needs to change tail geometry, across caliber transistions, in order for the scaled twist-rate to work.</p><p> </p><p>Best,</p><p>Noel</p></blockquote><p></p>
[QUOTE="noel carlson, post: 358985, member: 16138"] Mark, "... Not sure if that remains the same going to a different bore size?"... I missed your appendix last night, and it does bring up some interesting issues. Bore size, and twist-rate are essentially scalable. In 5.5+ caliber projectiles there is another factor that comes into play which has an effect that must be taken into account. The ZA relies heavily on tail geometry to maintain high velocity stability. In order for the tail design to be effective hovever, laminar flow needs to be preserved across it's surface. The Reynold's effect states, in essence, that an object of "A" diameter, at "B" velocity, will produce the same laminar/turbulence flow properties as an identical object of (1/2) "A" diameter, and (2) "B" velocity. To simulate a 50 caliber projectile at 2,500 fps, I would need to run a 25 caliber model at 5,000 fps. Bryan might want to weigh in here, but the practical result is that a projectile needs to change tail geometry, across caliber transistions, in order for the scaled twist-rate to work. Best, Noel [/QUOTE]
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