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Rifles, Reloading, Optics, Equipment
Reloading
Chambered Round Alignment to Bore; Neck Sized vs Full Length Sized
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<blockquote data-quote="Bart B" data-source="post: 647296" data-attributes="member: 5302"><p>Excellent reasoning and question!!!</p><p></p><p>Bullet balance is probably the hardest to get perfect from bullet to bullet. With all the mechanical parts of a bullet being perfect in dimensions, the microscopic difference in material density makes most of them a tiny bit unbalanced. And that causes different amounts of wobble as they go through the air. Sierra Bullets reported a small spread (1 to 2 percent) in measured BC's based ontime of flight between two points. Even when the velocities were identical going into the first test screen they wouild be different going through the last one; indicating different drag values. </p><p></p><p>Meplat uniforming of hollow points helps their aerodynamic shape. But I don't think it helps as much as some way to ensure all the bullets one shoots spin perfectly and have consistant BC's from muzzle to target. The only way to check a bullets balance is to spin them at very high speed.. </p><p></p><p>Some tests years ago spinning .3092" 185-gr. Lapua FMJRB match bullets at 30,000 rpm showed about 20% out of a box spun true; the rest were somewhat unbalanced. Some so much so they flew out of the collet chucked up in a Dremel Moto Tool that spun them. The good ones shot several 0.7" to 1.4" 10-shot groups at 600 yards from full length sized .308 Win. cases with neck diameters of about .332" fired in a virtual SAAMI spec chamber with a .344" neck.</p></blockquote><p></p>
[QUOTE="Bart B, post: 647296, member: 5302"] Excellent reasoning and question!!! Bullet balance is probably the hardest to get perfect from bullet to bullet. With all the mechanical parts of a bullet being perfect in dimensions, the microscopic difference in material density makes most of them a tiny bit unbalanced. And that causes different amounts of wobble as they go through the air. Sierra Bullets reported a small spread (1 to 2 percent) in measured BC's based ontime of flight between two points. Even when the velocities were identical going into the first test screen they wouild be different going through the last one; indicating different drag values. Meplat uniforming of hollow points helps their aerodynamic shape. But I don't think it helps as much as some way to ensure all the bullets one shoots spin perfectly and have consistant BC's from muzzle to target. The only way to check a bullets balance is to spin them at very high speed.. Some tests years ago spinning .3092" 185-gr. Lapua FMJRB match bullets at 30,000 rpm showed about 20% out of a box spun true; the rest were somewhat unbalanced. Some so much so they flew out of the collet chucked up in a Dremel Moto Tool that spun them. The good ones shot several 0.7" to 1.4" 10-shot groups at 600 yards from full length sized .308 Win. cases with neck diameters of about .332" fired in a virtual SAAMI spec chamber with a .344" neck. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Chambered Round Alignment to Bore; Neck Sized vs Full Length Sized
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