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Rifles, Reloading, Optics, Equipment
Reloading
Bullet Pulling Question
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<blockquote data-quote="Carey Farmer" data-source="post: 2618302" data-attributes="member: 122715"><p>I pull bullets all the time during load development. Have never been able to tell the difference between cases that have had bullets set once vs. set twice (unless I did a crap job of chamfering, and scratched up the bullets while seating them).</p><p></p><p>Well-understood behavior of metals is consistent with this observation. When you re-size the neck of a fired case, typically you yield the brass squeezing down on diameter. In this context "yield" just means you deform it enough that it doesn't spring back completely to the starting diameter. Then when you expand with a ball or mandrel, you'll typically use a mandrel large enough to open up the case neck enough that it doesn't spring back all the way to the post-resizing diameter. Then when you set the bullet, unless your expander diameter was the same as your bullet diameter, you yield it again. </p><p></p><p>But when you pull a bullet and then reset the same diameter bullet, the case necks move in the "elastic" range. In this context, "elastic" just means you don't yield the metal. That is, when you pull the bullet, it springs back smaller a thousandths or two, depending on its hardness. When you set a new bullet of the same diameter, the case neck doesn't yield: if you pull that second bullet, you'll find that the case neck springs back to the exact same diameter it did when you pulled the first bullet. </p><p></p><p>The key here is that the only neck tension the bullet actually "feels" is the difference between neck diameter with the bullet seated, and the spring-back diameter when the bullet is pulled. </p><p></p><p>You can measure all of this to confirm what your brass is doing. The bottom line is that neck tension shouldn't change when you pull and reset bullets, unless your chamfering is inadequate and scratches up the bullet during seating.</p></blockquote><p></p>
[QUOTE="Carey Farmer, post: 2618302, member: 122715"] I pull bullets all the time during load development. Have never been able to tell the difference between cases that have had bullets set once vs. set twice (unless I did a crap job of chamfering, and scratched up the bullets while seating them). Well-understood behavior of metals is consistent with this observation. When you re-size the neck of a fired case, typically you yield the brass squeezing down on diameter. In this context "yield" just means you deform it enough that it doesn't spring back completely to the starting diameter. Then when you expand with a ball or mandrel, you'll typically use a mandrel large enough to open up the case neck enough that it doesn't spring back all the way to the post-resizing diameter. Then when you set the bullet, unless your expander diameter was the same as your bullet diameter, you yield it again. But when you pull a bullet and then reset the same diameter bullet, the case necks move in the "elastic" range. In this context, "elastic" just means you don't yield the metal. That is, when you pull the bullet, it springs back smaller a thousandths or two, depending on its hardness. When you set a new bullet of the same diameter, the case neck doesn't yield: if you pull that second bullet, you'll find that the case neck springs back to the exact same diameter it did when you pulled the first bullet. The key here is that the only neck tension the bullet actually "feels" is the difference between neck diameter with the bullet seated, and the spring-back diameter when the bullet is pulled. You can measure all of this to confirm what your brass is doing. The bottom line is that neck tension shouldn't change when you pull and reset bullets, unless your chamfering is inadequate and scratches up the bullet during seating. [/QUOTE]
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Bullet Pulling Question
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