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Old March 10, 2013, 10:51 AM   #15
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 8,453
Reynolds, 'tis my opinion that while twist rate is half of stabilizing bullets, velocity out the barrel is the other half. It boils down to whatever combination gives the bullet's rpm rate best for its shape and weight. The rpm rate can be lower in warm weather than cold, but not by much. And the rpm's need to be a bit higher when bullets leave at faster muzzle velocityes.

Best accuracy to stabilize the bullet all the way to the target's typically at the low end of its rpm band. Any faster and the slight unbalance all bullets have starts to cause inaccuracy as they jump further off the muzzle axis when they exit.

Best example of this for best accuracy is a 240-gr. HPMK from a .308 case needs a 1:8 twist to stabilize it to 1000 yards. A 135-gr. HPMK from the same case needs a 1:16 twist to stabilize it to 300 yards.
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Last edited by Bart B.; March 10, 2013 at 12:09 PM.
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