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Rifles, Reloading, Optics, Equipment
Reloading
Velocity difference between new brass and fired brass
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<blockquote data-quote="Mikecr" data-source="post: 1826734" data-attributes="member: 1521"><p>Normal is actually opposite of that.</p><p>Say you work up a load with new/unfired cases to a near max. Those cases represent lowest capacity for charge (from that brass) so it's easy to assume that with the load more confined pressure will be higher. But that is a static notion rather than a dynamic reality.</p><p>If you are neck sizing only to reload those cases (now fired), and using that same 'near max' charge, you will see an<em><u> increase </u></em>in MV, and likely some pressure signs/problems.</p><p></p><p>Why is that? the fired & neck sized only case now represents larger volume for charge, and lower load density due to lower confinement, so the pressure should have dropped. But it doesn't. It goes up.</p><p>The reason is that <em>confinement</em> here is dynamic across time, either as cases expand,, or as case expansion is prevented (by the chamber).</p><p>Then add that powder burn rate is affected by this confinement in a way so nonlinear that it cannot even be credibly considered in a static sense.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 1826734, member: 1521"] Normal is actually opposite of that. Say you work up a load with new/unfired cases to a near max. Those cases represent lowest capacity for charge (from that brass) so it's easy to assume that with the load more confined pressure will be higher. But that is a static notion rather than a dynamic reality. If you are neck sizing only to reload those cases (now fired), and using that same 'near max' charge, you will see an[I][U] increase [/U][/I]in MV, and likely some pressure signs/problems. Why is that? the fired & neck sized only case now represents larger volume for charge, and lower load density due to lower confinement, so the pressure should have dropped. But it doesn't. It goes up. The reason is that [I]confinement[/I] here is dynamic across time, either as cases expand,, or as case expansion is prevented (by the chamber). Then add that powder burn rate is affected by this confinement in a way so nonlinear that it cannot even be credibly considered in a static sense. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Velocity difference between new brass and fired brass
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