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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: 1697074" data-attributes="member: 107925"><p>Update to earlier post: I mentioned that the internal forces on a bullet spinning at a high rate are working to tear the bullet apart - which, in the old days, with .220 Swift, happened. The bullets would disappear in a puff of lead smoke downrange, until they were built to take the forces trying to spin them apart.</p><p></p><p>I started working up a spreadsheet using Excel, my creaky memory of physics, and my fading concentration - and then it occurred to me that there's this thing called the Internet (D'oh!). I found an on-line centrifugal force calculator, and plugged in some figures for a Swift. Turns out the centrifugal acceleration is about 160,000 G's. The force - since the bullet is small and light, comes to about 1,250 lbs-ft. That's a 55 grain at 4,400 f/s in a 1/14" barrel. </p><p></p><p>For reference, 1,250 lbs-ft is the equivalent of the torque developed by the 5 liter V8 in a 2019 Ford F-150 - times 3 - although how you translate between the two beats me. It's pretty clear that if that on-line calculator is right, the materials toughness of that bullet, resisting the force trying to tear it apart in flight, is steroidal.</p><p></p><p>Just thought I'd throw this into the stew pot.</p></blockquote><p></p>
[QUOTE="GeorgeS, post: 1697074, member: 107925"] Update to earlier post: I mentioned that the internal forces on a bullet spinning at a high rate are working to tear the bullet apart - which, in the old days, with .220 Swift, happened. The bullets would disappear in a puff of lead smoke downrange, until they were built to take the forces trying to spin them apart. I started working up a spreadsheet using Excel, my creaky memory of physics, and my fading concentration - and then it occurred to me that there's this thing called the Internet (D'oh!). I found an on-line centrifugal force calculator, and plugged in some figures for a Swift. Turns out the centrifugal acceleration is about 160,000 G's. The force - since the bullet is small and light, comes to about 1,250 lbs-ft. That's a 55 grain at 4,400 f/s in a 1/14" barrel. For reference, 1,250 lbs-ft is the equivalent of the torque developed by the 5 liter V8 in a 2019 Ford F-150 - times 3 - although how you translate between the two beats me. It's pretty clear that if that on-line calculator is right, the materials toughness of that bullet, resisting the force trying to tear it apart in flight, is steroidal. Just thought I'd throw this into the stew pot. [/QUOTE]
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