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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Conclusions from data?
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<blockquote data-quote="Bart B" data-source="post: 127282" data-attributes="member: 5302"><p>I've not found anything significantly different in accuracy or muzzle velocity between the first and even the 25th firing of the same case. But it's common that the first shot from a clean barrel will leave slower than subsequent ones because jacket and powder fouling increase friction over the first shot which makes pressure higher and that makes the bullet go out faster.</p><p></p><p>As for the swings in muzzle velocity, some of the spread is caused by holding the rifle tighter or looser. A looser hold lets more recoil energy push the rifle further backwards which subtracts from the energy used to push the bullet out; the bullet leaves slower.</p><p></p><p>I've always got the lowest spreads in muzzle velocity by firing each round exactly 60 seconds apart. Each round would be chambered 15 seconds before shooting so they would all have the same amount of "warm up" time. Barrel cooling isn't an issue. If the barrel's properly stress relieved, it won't change point of impact as it heats up. Even with 30 to 40 shots from 30 caliber magnums burning 65 to 70 grains of powder, a properly fitted good barrel will not change impact going from cold to hot.</p><p></p><p>As for shots 10 and 11 being faster, I'd bet an ice cream sundae you held the rifle tighter 'cause it was raining and that made the bullets leave faster. Then when the rain stopped, you relaxed, held the rifle a bit looser and shot 12 left slower than the previous two.</p></blockquote><p></p>
[QUOTE="Bart B, post: 127282, member: 5302"] I've not found anything significantly different in accuracy or muzzle velocity between the first and even the 25th firing of the same case. But it's common that the first shot from a clean barrel will leave slower than subsequent ones because jacket and powder fouling increase friction over the first shot which makes pressure higher and that makes the bullet go out faster. As for the swings in muzzle velocity, some of the spread is caused by holding the rifle tighter or looser. A looser hold lets more recoil energy push the rifle further backwards which subtracts from the energy used to push the bullet out; the bullet leaves slower. I've always got the lowest spreads in muzzle velocity by firing each round exactly 60 seconds apart. Each round would be chambered 15 seconds before shooting so they would all have the same amount of "warm up" time. Barrel cooling isn't an issue. If the barrel's properly stress relieved, it won't change point of impact as it heats up. Even with 30 to 40 shots from 30 caliber magnums burning 65 to 70 grains of powder, a properly fitted good barrel will not change impact going from cold to hot. As for shots 10 and 11 being faster, I'd bet an ice cream sundae you held the rifle tighter 'cause it was raining and that made the bullets leave faster. Then when the rain stopped, you relaxed, held the rifle a bit looser and shot 12 left slower than the previous two. [/QUOTE]
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Rifles, Bullets, Barrels & Ballistics
Conclusions from data?
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