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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
How to test bullet expansion?
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<blockquote data-quote="AaronSkipDavidson" data-source="post: 2351609" data-attributes="member: 6373"><p>It doesn't decrease it's rotational speed nearly as fast as the velocity, mainly the difference is the rotational translation doesn't have to overcome pressure/form drag. </p><p></p><p>An approximating formula Geoffery Kolbe published for spin decay is:</p><p></p><p>Where:</p><p>Nm = the spin rate the bullet had at the muzzle</p><p>N = the spin rate of the bullet after your time of flight to the range of interest</p><p>t = time of flight in seconds from the muzzle to the current bullet position</p><p>d = bullet diameter in inches</p><p>e = natural logarithm base, 2.71828…</p><p></p><p>N = Nm × (-0.035 × t / d)^e</p></blockquote><p></p>
[QUOTE="AaronSkipDavidson, post: 2351609, member: 6373"] It doesn't decrease it's rotational speed nearly as fast as the velocity, mainly the difference is the rotational translation doesn't have to overcome pressure/form drag. An approximating formula Geoffery Kolbe published for spin decay is: Where: Nm = the spin rate the bullet had at the muzzle N = the spin rate of the bullet after your time of flight to the range of interest t = time of flight in seconds from the muzzle to the current bullet position d = bullet diameter in inches e = natural logarithm base, 2.71828… N = Nm × (-0.035 × t / d)^e [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
How to test bullet expansion?
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