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Rifles, Reloading, Optics, Equipment
Reloading
loading for a ar10?
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<blockquote data-quote="Bart B" data-source="post: 1122684" data-attributes="member: 5302"><p>Full length size your fired cases for best accuracy; that's been proved for decades. It's important that the fired case shoulder be set back about .003" for good functioning in semiautos as well as decent case life; 4 to 5 reloads is about maximum. You'll need a case headspace gauge to measure cases; RCBS Precision Mic or Hornady LNL, for example. Or just use a half inch long nylon bushing with a 3/8ths inch hole in it to put on the case shoulder then measure with calipers.</p><p></p><p>RCBS or Redding full length bushing dies are good, but use a bushing diameter about .002" smaller than that of a loaded round's neck diameter. Don't crimp case mouths into bullets; a sure cause of accuracy loss. Seat bullets to function well when rounds are used with magazines. For single round loading, seat bullets about .010" short of touching the rifling.</p><p></p><p>It's almost impossible to tell real pressure levels without a real piezo transducer pressure system, such as those from RSI. Visible signs of primer or case changes are only approximate, but better than nothing. If you stick to near max loading data, you should be fine. </p><p></p><p>Powder wears out barrels, bullet speed does not. A .308 Win will get 3000 rounds of best accuracy shooting 150-gr. bullets out at 3000 fps from a long barrel with 45 grains of powder. A 30 caliber magnum shooting 200-gr. bullets out at 3000 fps with 65 grains of powder has 1200 rounds of barrel life with equal accuracy. Shooting 140's from a 6.5x.284 out at 3000 fps with 47 grains of powder gets 750 rounds of barrel life with the same best accuracy. All of them having the same peak pressure.</p><p></p><p>Unless your AR10's bolt face has been squared up properly with the chamber axis, new cases will typically shoot bullets more accurate than reloaded ones. When first fired, case heads tend to flatten against the bolt face; if that face ain't square, the case head's now out of square. Resizing them doesn't square the head back up. They'll slam at different places around the bolt face each time they're fired. That can cause up to 1 MOA accuracy degradation.</p><p></p><p>I don't know how long your barrel is, so I suggest using bullets in the 175 to 185 range. Sierra or Berger match bullets will shoot most accurate, but only if they're a few ten-thousandths inch bigger in diameter than the barrel's groove diameter. 42 or 43 grains of IMR4064 under either one should do well.</p></blockquote><p></p>
[QUOTE="Bart B, post: 1122684, member: 5302"] Full length size your fired cases for best accuracy; that's been proved for decades. It's important that the fired case shoulder be set back about .003" for good functioning in semiautos as well as decent case life; 4 to 5 reloads is about maximum. You'll need a case headspace gauge to measure cases; RCBS Precision Mic or Hornady LNL, for example. Or just use a half inch long nylon bushing with a 3/8ths inch hole in it to put on the case shoulder then measure with calipers. RCBS or Redding full length bushing dies are good, but use a bushing diameter about .002" smaller than that of a loaded round's neck diameter. Don't crimp case mouths into bullets; a sure cause of accuracy loss. Seat bullets to function well when rounds are used with magazines. For single round loading, seat bullets about .010" short of touching the rifling. It's almost impossible to tell real pressure levels without a real piezo transducer pressure system, such as those from RSI. Visible signs of primer or case changes are only approximate, but better than nothing. If you stick to near max loading data, you should be fine. Powder wears out barrels, bullet speed does not. A .308 Win will get 3000 rounds of best accuracy shooting 150-gr. bullets out at 3000 fps from a long barrel with 45 grains of powder. A 30 caliber magnum shooting 200-gr. bullets out at 3000 fps with 65 grains of powder has 1200 rounds of barrel life with equal accuracy. Shooting 140's from a 6.5x.284 out at 3000 fps with 47 grains of powder gets 750 rounds of barrel life with the same best accuracy. All of them having the same peak pressure. Unless your AR10's bolt face has been squared up properly with the chamber axis, new cases will typically shoot bullets more accurate than reloaded ones. When first fired, case heads tend to flatten against the bolt face; if that face ain't square, the case head's now out of square. Resizing them doesn't square the head back up. They'll slam at different places around the bolt face each time they're fired. That can cause up to 1 MOA accuracy degradation. I don't know how long your barrel is, so I suggest using bullets in the 175 to 185 range. Sierra or Berger match bullets will shoot most accurate, but only if they're a few ten-thousandths inch bigger in diameter than the barrel's groove diameter. 42 or 43 grains of IMR4064 under either one should do well. [/QUOTE]
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