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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Barrel Wear
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<blockquote data-quote="Kevin Thomas" data-source="post: 481831" data-attributes="member: 15748"><p>Fitch,</p><p> </p><p>A very reasonable and in-depth summary here. I alluded to the other variables, and you highlighted some of these. You obviously have a bore scope, as do I, but for those who've never used one, it's enlightening to say the least. All the action takes place in the first few inches of the bore, and in the first few milliseconds as the bullet begins to move. Not at all uncommon to find a throat that looks like a mile of really bad asphalt, while the remainder of the barrel looks like it's never seen a round fired.</p><p> </p><p>You covered the flame temps, and I'd touched on the same. JohnnyK mentioned two powders with similar burn rates (and he's perfectly correct there), but didn't mention that the IMR is a single based propellant, while the H414 is double based powder. This is one of the differences I highlighted in pointing out that it's a sliding scale with a number of variables to be considered.</p><p> </p><p>This also goes a long way in explaining why heavy bullets are so much harder on barrels (specifically, the throats) than lighter ones. Longer dwell time, as the heavier bullet has more inertia to overcome before it begins to move, gives those hot gasses and high pressures a good bit more time to allow them to work their damage. Once they begin moving, the rest of the bore is comparatively undamaged by the bullet's passage. </p><p> </p><p>Good write up.</p></blockquote><p></p>
[QUOTE="Kevin Thomas, post: 481831, member: 15748"] Fitch, A very reasonable and in-depth summary here. I alluded to the other variables, and you highlighted some of these. You obviously have a bore scope, as do I, but for those who've never used one, it's enlightening to say the least. All the action takes place in the first few inches of the bore, and in the first few milliseconds as the bullet begins to move. Not at all uncommon to find a throat that looks like a mile of really bad asphalt, while the remainder of the barrel looks like it's never seen a round fired. You covered the flame temps, and I'd touched on the same. JohnnyK mentioned two powders with similar burn rates (and he's perfectly correct there), but didn't mention that the IMR is a single based propellant, while the H414 is double based powder. This is one of the differences I highlighted in pointing out that it's a sliding scale with a number of variables to be considered. This also goes a long way in explaining why heavy bullets are so much harder on barrels (specifically, the throats) than lighter ones. Longer dwell time, as the heavier bullet has more inertia to overcome before it begins to move, gives those hot gasses and high pressures a good bit more time to allow them to work their damage. Once they begin moving, the rest of the bore is comparatively undamaged by the bullet's passage. Good write up. [/QUOTE]
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