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Long Range Hunting & Shooting
Effect of Bullet Spin on Terminal Performance
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<blockquote data-quote="GeorgeS" data-source="post: 1695284" data-attributes="member: 107925"><p>Yes - the presumption, of course, is that the "black talon" holds together. Surprisingly, bullets hold together quite well. I have a load that uses 50 grain SBTHP bullets out of a .220 Swift, with a muzzle velocity of 4,400 f/s - got it out of an issue of Handloader back ages ago. In my 1:14 twist Ruger 77, that bullet is spinning 4,400*12/14 rps =226,286 rpm. Yet it holds together just fine to the target. At the target, however, it explodes violently from both impact speed and rotational force. In the old days, with less well-designed and manufactured bullets, .220 Swifts had a reputation for bullets blowing up midway to the target at only 4,000 f/s muzzle velocity.</p><p></p><p>So the presumption in my post was that a well-designed modern bullet would hold together - particularly a skived monolithic - and wreak havoc throughout the wound channel. Your example of a 6.5 at 2,600 f/s out of a 1:7.5 would not only be spinning faster (268,000 rpm), but the larger diameter of the bullet would result in tremendous internal forces on the bullet trying to tear it apart - yet they hold together well. Modern bullets are very well built.</p><p></p><p>It should also be noted that as a bullet expands, the expansion itself - owing to conservation of momentum - slows the bullet's rotation, not just the drag from the now-larger diameter. It's the opposite phenomenon we see when a spinning skater pulls in his or her arms, increasing the rotational rate of the spin, then extending arms to slow again.</p><p></p><p>But there is no question that the energy imparted longitudinally by the bullet transit along its path within the target far exceeds the energy imparted by rotational effects. At in-target velocities above about 2,200 f/s, the hydrostatic effects are very significant.</p></blockquote><p></p>
[QUOTE="GeorgeS, post: 1695284, member: 107925"] Yes - the presumption, of course, is that the "black talon" holds together. Surprisingly, bullets hold together quite well. I have a load that uses 50 grain SBTHP bullets out of a .220 Swift, with a muzzle velocity of 4,400 f/s - got it out of an issue of Handloader back ages ago. In my 1:14 twist Ruger 77, that bullet is spinning 4,400*12/14 rps =226,286 rpm. Yet it holds together just fine to the target. At the target, however, it explodes violently from both impact speed and rotational force. In the old days, with less well-designed and manufactured bullets, .220 Swifts had a reputation for bullets blowing up midway to the target at only 4,000 f/s muzzle velocity. So the presumption in my post was that a well-designed modern bullet would hold together - particularly a skived monolithic - and wreak havoc throughout the wound channel. Your example of a 6.5 at 2,600 f/s out of a 1:7.5 would not only be spinning faster (268,000 rpm), but the larger diameter of the bullet would result in tremendous internal forces on the bullet trying to tear it apart - yet they hold together well. Modern bullets are very well built. It should also be noted that as a bullet expands, the expansion itself - owing to conservation of momentum - slows the bullet's rotation, not just the drag from the now-larger diameter. It's the opposite phenomenon we see when a spinning skater pulls in his or her arms, increasing the rotational rate of the spin, then extending arms to slow again. But there is no question that the energy imparted longitudinally by the bullet transit along its path within the target far exceeds the energy imparted by rotational effects. At in-target velocities above about 2,200 f/s, the hydrostatic effects are very significant. [/QUOTE]
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