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Hunting
Long Range Hunting & Shooting
Barrel length and twist question
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<blockquote data-quote="Randy Tidwell" data-source="post: 1617715" data-attributes="member: 109136"><p>Twist rate is not related to bullet weight, it is relative to the length of the bullet. The longer the bullet, the faster it needs to spin. Hence copper bullets shoot better with faster twists.</p><p></p><p>A number of years ago we were having trouble with VLDs coming apart at about 3200fps. I put together a spread sheet to calculate rpm of a bullet with different twist rates. I was shocked when I plugged in a bullet traveling at 3150 fps out of an 8 twist, 312,000 rpm. Not a typo, 312 thousand rpm.</p><p></p><p>I didn't believe it, so I game the math problem my son (Masters in Math), he confirmed my calculations. No wonder these thin jacketed pills come apart if you push them.</p><p></p><p>I still have the spread sheet if anyone wants it. </p><p></p><p>So in response to OP, if he only wants to shoot 150s, a 10 twist all he needs. As far as length, with powders avail today, 26" would be the max I would consider. Since he will be installing a break, I would be doing a 24-25". Carrying a rifle with anything longer than 26" OAL is pain in the ***. JMHO</p></blockquote><p></p>
[QUOTE="Randy Tidwell, post: 1617715, member: 109136"] Twist rate is not related to bullet weight, it is relative to the length of the bullet. The longer the bullet, the faster it needs to spin. Hence copper bullets shoot better with faster twists. A number of years ago we were having trouble with VLDs coming apart at about 3200fps. I put together a spread sheet to calculate rpm of a bullet with different twist rates. I was shocked when I plugged in a bullet traveling at 3150 fps out of an 8 twist, 312,000 rpm. Not a typo, 312 thousand rpm. I didn't believe it, so I game the math problem my son (Masters in Math), he confirmed my calculations. No wonder these thin jacketed pills come apart if you push them. I still have the spread sheet if anyone wants it. So in response to OP, if he only wants to shoot 150s, a 10 twist all he needs. As far as length, with powders avail today, 26" would be the max I would consider. Since he will be installing a break, I would be doing a 24-25". Carrying a rifle with anything longer than 26" OAL is pain in the ***. JMHO [/QUOTE]
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Barrel length and twist question
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