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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
is copper jacket spinning around lead core during flight
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<blockquote data-quote="QuietTexan" data-source="post: 2276752" data-attributes="member: 116181"><p>The heat transfer coefficient of lead is approximately 10x that of copper, would that create a situation where the jacket is significantly hotter than the core in the very short time frame we're dealing with because the core can't absorb the heat any faster? Maybe the boundary layer is melted or softens enough to slip but still keeping to core moving within some high percentage of the jackets rotation. I was generally thinking longitudinally about the core and jacket down the bearing surface with essentially a cylindrical shear boundary around the entire circumference of the core, but your point about the base of the core heating differently than the nose would also come into play.</p><p></p><p>The core is probably something like a 90-94% lead, 5% tin, 1-4% antimony alloy. Jacket is probably 90-95% copper and 5-10% zinc.</p><p></p><p></p><p>I think is what also Magnum is getting at. Something happens to the lead core, maybe even isolated to the back portion of the core, melting or softening or slipping or something, that allows the core to move independently from the jacket at impact as is proven by flow from the core moving forward as the jacket is decelerating upon impact.</p><p></p><p>Maybe the core/jacket boundary up along the ogive isn't heated as much by air friction as the base is by the powder charge, and while the base of the core could be melting/softening it's held in place until the meplat opens and allows the solid front of the core to keep moving forward as the jacket sheds?</p></blockquote><p></p>
[QUOTE="QuietTexan, post: 2276752, member: 116181"] The heat transfer coefficient of lead is approximately 10x that of copper, would that create a situation where the jacket is significantly hotter than the core in the very short time frame we're dealing with because the core can't absorb the heat any faster? Maybe the boundary layer is melted or softens enough to slip but still keeping to core moving within some high percentage of the jackets rotation. I was generally thinking longitudinally about the core and jacket down the bearing surface with essentially a cylindrical shear boundary around the entire circumference of the core, but your point about the base of the core heating differently than the nose would also come into play. The core is probably something like a 90-94% lead, 5% tin, 1-4% antimony alloy. Jacket is probably 90-95% copper and 5-10% zinc. I think is what also Magnum is getting at. Something happens to the lead core, maybe even isolated to the back portion of the core, melting or softening or slipping or something, that allows the core to move independently from the jacket at impact as is proven by flow from the core moving forward as the jacket is decelerating upon impact. Maybe the core/jacket boundary up along the ogive isn't heated as much by air friction as the base is by the powder charge, and while the base of the core could be melting/softening it's held in place until the meplat opens and allows the solid front of the core to keep moving forward as the jacket sheds? [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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is copper jacket spinning around lead core during flight
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