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Extreme Long Range Hunting & Shooting (ELR)
Twist rates for elr?
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<blockquote data-quote="Milepost" data-source="post: 1636857" data-attributes="member: 104022"><p>Although we are generally looking at the ideal twist rates per caliber and construction/shape of a bullet. I would like to mention that the exit speed at which we are shooting the bullet at will also effect the exit RPM of the the bullet too. The 20 to 1 twist is not a ratio that is set in stone! It is the SG to get thru the TRANSONIC region that we are trying to achieve here. Also remember that the ideal SG is also effected by the density of the material too!</p><p>Simply put:</p><p>1) The twist rate sets up the rpm of the bullet at a given exit speed. The bullet is now a gyro.... If the ideal twist rate is at 20:1 for 3000fps we therefore will not need as much twist rate if the bullet is exiting at say 3300fps because the rpm of the said bullet is now 10% higher.</p><p>2) The 20:1 twist rate that is used is for copper alloy bullets which have a density of around 8.8. Bronze alloy is around 8.4, and heavy lead jacketed bullets are around 10. The higher the density of material the less twist rate that will be needed.... This is because the the resistance to a change in direction of a gyro is related to the mass and its distance from the spin axis (center of rotation) and its speed of rotation (RPM).</p><p></p><p>Remember too that these super fast Hyper stabilized twist rates are so the bullets can get thru the transonic region with a minimum of fuss. If we can keep the bullet above the transonic region ( Mach 1.2 ) we will not need such a high twist rate to keep the bullet stable in flight.</p><p></p><p>The twist rate you pick should be chosen by the JOB you are trying to accomplish. The twist rate for K2m is different from what is considered ideal for a 1000 yard bench rest F class shooter and is VERY different than what is needed for a hunter....</p></blockquote><p></p>
[QUOTE="Milepost, post: 1636857, member: 104022"] Although we are generally looking at the ideal twist rates per caliber and construction/shape of a bullet. I would like to mention that the exit speed at which we are shooting the bullet at will also effect the exit RPM of the the bullet too. The 20 to 1 twist is not a ratio that is set in stone! It is the SG to get thru the TRANSONIC region that we are trying to achieve here. Also remember that the ideal SG is also effected by the density of the material too! Simply put: 1) The twist rate sets up the rpm of the bullet at a given exit speed. The bullet is now a gyro.... If the ideal twist rate is at 20:1 for 3000fps we therefore will not need as much twist rate if the bullet is exiting at say 3300fps because the rpm of the said bullet is now 10% higher. 2) The 20:1 twist rate that is used is for copper alloy bullets which have a density of around 8.8. Bronze alloy is around 8.4, and heavy lead jacketed bullets are around 10. The higher the density of material the less twist rate that will be needed.... This is because the the resistance to a change in direction of a gyro is related to the mass and its distance from the spin axis (center of rotation) and its speed of rotation (RPM). Remember too that these super fast Hyper stabilized twist rates are so the bullets can get thru the transonic region with a minimum of fuss. If we can keep the bullet above the transonic region ( Mach 1.2 ) we will not need such a high twist rate to keep the bullet stable in flight. The twist rate you pick should be chosen by the JOB you are trying to accomplish. The twist rate for K2m is different from what is considered ideal for a 1000 yard bench rest F class shooter and is VERY different than what is needed for a hunter.... [/QUOTE]
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Twist rates for elr?
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