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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Excessive Throat Growth Question
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<blockquote data-quote="Bart B" data-source="post: 620959" data-attributes="member: 5302"><p>OK. Next time use this info and formula to calculate barrel life for a 1/2 MOA rifle from the get-go so you'll know what to expect:</p><p></p><p>Barrel life's about 3000 rounds when there's one grain of powder for each square millimeter of the bore's cross sectional area. For a 7mm, it's bore area's 38.5 square millimeters; the 7mm-08 gets about that much barrel life. Double the powder charge with a larger case capacity and barrel life's cut by 75%; 750 rounds is all one gets at 1/2 MOA accuracy for rifle cartridges working at normal max loads in the 55,000 CUP range. With hotter loads, barrel life will be even shorter. It's an inverse square law that seems to work pretty well.</p><p></p><p>How many grains of powder have you used with your 7mm AM's loads?</p><p></p><p>PS: If the barrel's best accuracy is 3/4 to 1 MOA at the beginning, one will get 3 to 4 times the barrel life the above formula produces.</p></blockquote><p></p>
[QUOTE="Bart B, post: 620959, member: 5302"] OK. Next time use this info and formula to calculate barrel life for a 1/2 MOA rifle from the get-go so you'll know what to expect: Barrel life's about 3000 rounds when there's one grain of powder for each square millimeter of the bore's cross sectional area. For a 7mm, it's bore area's 38.5 square millimeters; the 7mm-08 gets about that much barrel life. Double the powder charge with a larger case capacity and barrel life's cut by 75%; 750 rounds is all one gets at 1/2 MOA accuracy for rifle cartridges working at normal max loads in the 55,000 CUP range. With hotter loads, barrel life will be even shorter. It's an inverse square law that seems to work pretty well. How many grains of powder have you used with your 7mm AM's loads? PS: If the barrel's best accuracy is 3/4 to 1 MOA at the beginning, one will get 3 to 4 times the barrel life the above formula produces. [/QUOTE]
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Excessive Throat Growth Question
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