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Rifles, Reloading, Optics, Equipment
Reloading
I gotta ask....
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<blockquote data-quote="Bart B" data-source="post: 105524" data-attributes="member: 5302"><p>[ QUOTE ]</p><p>Leaving a portion of the bottom of the neck unsized can have a few benefits. One reason is that the unsized section will sort of center the neck up when chambered, also leaving the bottom unsized can eliminate the problem of the dougnut. The doughnut would still be there but without that part of the neck sized down it does not have its usual effects. </p><p></p><p>[/ QUOTE ]Note that a rimless bottleneck case is centered at the chamber's front end when fired by one of two things: one is a spring loaded ejector pushing it as far forward as possible, the other is the firing pin driving the case forward. Both instances cause the tapered case shoulder to center in the chamber shoulder. Whatever neck diameter or alignment there is doesn't matter; the case and chamber shoulder fit centers the round's front end in the chamber. One can learn this by measuring a primed case's headspace, then popping that primed case in the chamber, then measuring it again. The 'popped case' headspace will be up to 1 or 2 thousandths shorter; evidence it got driven into the chamber shoulder hard enough to set the shoulder back.</p><p></p><p>I and others have full-length sized many a rimless bottleneck case 60 to 100 times with max loads and never had a 'doughnut' problem. But the shoulder can't be set back in sizing more than three thousandths to do this.</p><p></p><p>And if you use a full-length sizing die to size only part of the neck, the shoulder may be set forward far enough to prevent the case from easily chambering. Partial neck sizing is typically best done with neck-only dies.</p></blockquote><p></p>
[QUOTE="Bart B, post: 105524, member: 5302"] [ QUOTE ] Leaving a portion of the bottom of the neck unsized can have a few benefits. One reason is that the unsized section will sort of center the neck up when chambered, also leaving the bottom unsized can eliminate the problem of the dougnut. The doughnut would still be there but without that part of the neck sized down it does not have its usual effects. [/ QUOTE ]Note that a rimless bottleneck case is centered at the chamber's front end when fired by one of two things: one is a spring loaded ejector pushing it as far forward as possible, the other is the firing pin driving the case forward. Both instances cause the tapered case shoulder to center in the chamber shoulder. Whatever neck diameter or alignment there is doesn't matter; the case and chamber shoulder fit centers the round's front end in the chamber. One can learn this by measuring a primed case's headspace, then popping that primed case in the chamber, then measuring it again. The 'popped case' headspace will be up to 1 or 2 thousandths shorter; evidence it got driven into the chamber shoulder hard enough to set the shoulder back. I and others have full-length sized many a rimless bottleneck case 60 to 100 times with max loads and never had a 'doughnut' problem. But the shoulder can't be set back in sizing more than three thousandths to do this. And if you use a full-length sizing die to size only part of the neck, the shoulder may be set forward far enough to prevent the case from easily chambering. Partial neck sizing is typically best done with neck-only dies. [/QUOTE]
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Reloading
I gotta ask....
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