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Rifles, Reloading, Optics, Equipment
Reloading
6.5-06 vs 6.5X284 vs 6.5 Sherman
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<blockquote data-quote="Bart B" data-source="post: 511815" data-attributes="member: 5302"><p>The term "overbore" is often used, but how it's determined is usually based on guessing and opinion. Which is why I asked a noted riflesmith many years ago if there's any standard it's supposed to be referenced to.</p><p></p><p>Elmer Shook told me that bore capacity for a given bore diameter is one grain of powder for each square millimeter of the bore diameter's cross sectional area. And any caliber barrel shooting max loads whose powder charge weight producing best accuracy was at bore capacity would deliver about 3000 rounds of best accuracy. This is for barrels that start out shooting no worse than 1/4 MOA at 100 yards. Less accurate barrels tend to have longer barrel lives.</p><p></p><p>So I did some checking on this. Sure enough, popular 22, 24, 26, 28 and 30 caliber competition cartridges whose powder charge weight was at their bore capacity seemed to last about 3000 rounds of best accuracy. Double the charge weight for a given caliber and barrel life is reduced to 1/4th as many rounds.</p><p></p><p>If Kevin Thomas reads this, maybe he would share with us how often the test barrels in Sierra Bullets' rail guns got replaced when their accuracy level with "standards" dropped off.</p></blockquote><p></p>
[QUOTE="Bart B, post: 511815, member: 5302"] The term "overbore" is often used, but how it's determined is usually based on guessing and opinion. Which is why I asked a noted riflesmith many years ago if there's any standard it's supposed to be referenced to. Elmer Shook told me that bore capacity for a given bore diameter is one grain of powder for each square millimeter of the bore diameter's cross sectional area. And any caliber barrel shooting max loads whose powder charge weight producing best accuracy was at bore capacity would deliver about 3000 rounds of best accuracy. This is for barrels that start out shooting no worse than 1/4 MOA at 100 yards. Less accurate barrels tend to have longer barrel lives. So I did some checking on this. Sure enough, popular 22, 24, 26, 28 and 30 caliber competition cartridges whose powder charge weight was at their bore capacity seemed to last about 3000 rounds of best accuracy. Double the charge weight for a given caliber and barrel life is reduced to 1/4th as many rounds. If Kevin Thomas reads this, maybe he would share with us how often the test barrels in Sierra Bullets' rail guns got replaced when their accuracy level with "standards" dropped off. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
6.5-06 vs 6.5X284 vs 6.5 Sherman
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