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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Opinions wanted, or facts...About 6.5x284 or 260 barrel life
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<blockquote data-quote="Bart B" data-source="post: 650761" data-attributes="member: 5302"><p>Over four decades of high power competition, I noted how long barrels lasted for the top competitors. Their barrels started out with 1/4 MOA accuracy at 200 yards. Calibers ranged from 30 down to 24. Did some research on what the benchrester's 22 and 24 caliber barrels did for barrel life as well. Then I took the data and came up with a formula that uses powder charge weight in grains and the bore's cross sectional area in square millimeters. One thing stood out among all others; when 1 grain of powder was used for each square millimeter of the bore area, accuracy at this level lasted for about 3000 rounds. Some of the top competitors would notice that after about 1500 rounds, the accuracy had degraded about 20 to 30 percent; 'twas about 5/16 MOA accuracy at that point. Good enough for all but the top level matches such as the Nationals and Regional ones. Sierra Bullets' tech agreed with my calculations; their .308 Win. test barrels got replaced at about 3000 rounds and holding about 1/4 MOA accuracy burning one grain of powde for each of its bore area of 46 square millimeters.</p><p></p><p>A 6.5mm bore has about 33 square millimeters of area. Cartridges burning 33 grains of powder shooting 1/4 MOA will get about 3000 rounds of barrel life. Increase the powder charge 41% and barrel life gets cut in half. Double it and life is now one fourth as much. </p><p></p><p> No wonder the .243 Win. case got about 1500 rounds of best accuracy when it was first used. The top barrel makers agreed with this when I asked them what the .,243 was getting in their barrels. Its "bore capacity (area)" is 28 grains. But the 6PPC round in benchrest gets about 3000 rounds of good accuracy burning 28 grains of powder.</p><p></p><p>The 6.5x.284 has a bore area of 33 square millimeters. Burning 47 or so grains of powder's been producing about 1500 rounds of best accuracy in competition. And benchresters using this round sometimes rebarrel at 700 to 800 rounds when they see it's accuracy drop off a bit. My own 6.5mm barrel, a .264 Win. Mag., lasted 640 rounds of best accuracy burning 72 grains of powder for each shot.</p><p></p><p>For rifles getting around 1/2 MOA accuracy, barrel life will be about twice as much. A 1 MOA rifle and ammo may well get three to four times as many rounds of barrel life before loss of accuracy's noticed.</p></blockquote><p></p>
[QUOTE="Bart B, post: 650761, member: 5302"] Over four decades of high power competition, I noted how long barrels lasted for the top competitors. Their barrels started out with 1/4 MOA accuracy at 200 yards. Calibers ranged from 30 down to 24. Did some research on what the benchrester's 22 and 24 caliber barrels did for barrel life as well. Then I took the data and came up with a formula that uses powder charge weight in grains and the bore's cross sectional area in square millimeters. One thing stood out among all others; when 1 grain of powder was used for each square millimeter of the bore area, accuracy at this level lasted for about 3000 rounds. Some of the top competitors would notice that after about 1500 rounds, the accuracy had degraded about 20 to 30 percent; 'twas about 5/16 MOA accuracy at that point. Good enough for all but the top level matches such as the Nationals and Regional ones. Sierra Bullets' tech agreed with my calculations; their .308 Win. test barrels got replaced at about 3000 rounds and holding about 1/4 MOA accuracy burning one grain of powde for each of its bore area of 46 square millimeters. A 6.5mm bore has about 33 square millimeters of area. Cartridges burning 33 grains of powder shooting 1/4 MOA will get about 3000 rounds of barrel life. Increase the powder charge 41% and barrel life gets cut in half. Double it and life is now one fourth as much. No wonder the .243 Win. case got about 1500 rounds of best accuracy when it was first used. The top barrel makers agreed with this when I asked them what the .,243 was getting in their barrels. Its "bore capacity (area)" is 28 grains. But the 6PPC round in benchrest gets about 3000 rounds of good accuracy burning 28 grains of powder. The 6.5x.284 has a bore area of 33 square millimeters. Burning 47 or so grains of powder's been producing about 1500 rounds of best accuracy in competition. And benchresters using this round sometimes rebarrel at 700 to 800 rounds when they see it's accuracy drop off a bit. My own 6.5mm barrel, a .264 Win. Mag., lasted 640 rounds of best accuracy burning 72 grains of powder for each shot. For rifles getting around 1/2 MOA accuracy, barrel life will be about twice as much. A 1 MOA rifle and ammo may well get three to four times as many rounds of barrel life before loss of accuracy's noticed. [/QUOTE]
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Opinions wanted, or facts...About 6.5x284 or 260 barrel life
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