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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
School me on case design..
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<blockquote data-quote="Bart B" data-source="post: 619113" data-attributes="member: 5302"><p>First off, I'm convinced that the slower a powder burns, the more muzzle velocity spread there is. This applies to powders slower than IMR4350 which is about 2/3rds down the list going from fastest to slowest powders. And to cases holding no more than about 80 grains of it. Increased velocity spread causes more vertical shot stringing.</p><p></p><p>Second, "harmonics" is not the correct term and may be confusing some folks. A barrel has a fundamental, or resonant, frequency it whips (vibrates) at. A harmonic is just a multiple of that frequency. The greatest change in the bore angle at the muzzle happens at the fundamental frequency. The harmonic multiples are much lower in size and contribute virtually zero to any accuracy improvements or degradation. </p><p></p><p>Third, every barrel whips the same for each shot regardless of what load's used. It's like smacking a guitar string with a ball peen hammer; it makes the same note (very loud) as barely plucking it with your pinkie (very soft). Rifle barrels respond the same way. So how much a barrel whips has little to do with accuracy as long as it whips the same for each shot. But the timing of when the bullet leaves is important....so use the right one with the right amount of the right powder.</p></blockquote><p></p>
[QUOTE="Bart B, post: 619113, member: 5302"] First off, I'm convinced that the slower a powder burns, the more muzzle velocity spread there is. This applies to powders slower than IMR4350 which is about 2/3rds down the list going from fastest to slowest powders. And to cases holding no more than about 80 grains of it. Increased velocity spread causes more vertical shot stringing. Second, "harmonics" is not the correct term and may be confusing some folks. A barrel has a fundamental, or resonant, frequency it whips (vibrates) at. A harmonic is just a multiple of that frequency. The greatest change in the bore angle at the muzzle happens at the fundamental frequency. The harmonic multiples are much lower in size and contribute virtually zero to any accuracy improvements or degradation. Third, every barrel whips the same for each shot regardless of what load's used. It's like smacking a guitar string with a ball peen hammer; it makes the same note (very loud) as barely plucking it with your pinkie (very soft). Rifle barrels respond the same way. So how much a barrel whips has little to do with accuracy as long as it whips the same for each shot. But the timing of when the bullet leaves is important....so use the right one with the right amount of the right powder. [/QUOTE]
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School me on case design..
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