Dempsey:
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<br>There are some other interesting facts and consequences of spinning bullets.
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<br>* The twist rate in most rifles is actually not suited for the full range of grain weights available.
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<br>* The twist rate is only one element of determining the numbers of revolutions .
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<br>* The velocity also governs the rpm's.
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<br>* The twist rates for bigger bullets are slower than those of smaller bullets.
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<br>* Small bullets spun too fast will shed their cladding and disintegratre due to excessive centrifugal force.
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<br>* Bullet spin rate has been related to penetration depth in animals!
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<br>It is beneficial to use a twist rate calculator, of which there are many on the I-net, to see what happens when bullet calibers and velocities change:
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<br>Caliber 30-06 (.308" )
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<br>Vel/FPM......Twist rate......RPM's
<br>2000...........15.................1600
<br>2500...........16.................1875
<br>3000...........17.................2000
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<br>Caliber .22-250 ( .244 )
<br>Vel/FPM......Twist rate......RPM's
<br>2000............7.................3428
<br>2500............8.................3750
<br>3000............9.................4000
<br>3500...........10................4200
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<br>Some bench rest shooters select the slowest rate that will still shoot a bullet accurately.
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<br>When selecting a hunting rifle the grain weight most likely to be used most of the time should be matched to the appropriate twist rate to achieve optimum performance. Usually the Manufacturers only offer a predetermined twist rate, thus rebarreled rifles or rifles custom build will be the only available opportunity to choose the preferred rate.
<br>
<br>Bill Tibbe
