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Rifles, Reloading, Optics, Equipment
Reloading
For Those That Weigh Brass
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<blockquote data-quote="Bart B" data-source="post: 516540" data-attributes="member: 5302"><p>I think it's exactly true. Especially if you discount the case head which doesn't expand any significant amount up to almost where the pressure ring is.</p><p></p><p>Yes, that's the way it is.</p><p></p><p>I'm working on a spreadsheet to calculate chamber and case volume. Rough estimate for a 26-inch long 7mm Rem. Mag barrel shows the case volume is about 20% of the bore volume. A 1:5 ratio's quite a bit.</p><p></p><p>I don't think so. The bullet gets pushed out of the neck and the case neck expands behind it. There's no force on the inside of the case neck where it touches the bullet. Virtually all the force is against the base of the bullet which pushes it out of the case neck then into the rifling. Once the bullet heel's clear of the case mouth, then the whole neck's expanded all the way out to the chamber's neck wall.</p><p></p><p>What about the case with tissue stuffed in between powder and bullet? This puts near twice as much powder closer to the flash hole. More powder gets ignited in those first few microseconds than a case half full of powder where half the powder's in the front half of the case body. </p><p>Again, right on these, too.</p><p></p><p>Probably with neck only sized cases. With my full length sized ones there's no noticable difference in the chrony tests I did. Never tested the diffference using neck only sizing. With the same load producing the same peak pressure, they all will expand to a perfect fit in the chamber, all will have the same case volume. New cases will spring back more than fired cases. The more times a case gets neck sized, the larger its body is after each firing, both in headspace and diameter. Proper full length sized cases don't do that.</p></blockquote><p></p>
[QUOTE="Bart B, post: 516540, member: 5302"] I think it's exactly true. Especially if you discount the case head which doesn't expand any significant amount up to almost where the pressure ring is. Yes, that's the way it is. I'm working on a spreadsheet to calculate chamber and case volume. Rough estimate for a 26-inch long 7mm Rem. Mag barrel shows the case volume is about 20% of the bore volume. A 1:5 ratio's quite a bit. I don't think so. The bullet gets pushed out of the neck and the case neck expands behind it. There's no force on the inside of the case neck where it touches the bullet. Virtually all the force is against the base of the bullet which pushes it out of the case neck then into the rifling. Once the bullet heel's clear of the case mouth, then the whole neck's expanded all the way out to the chamber's neck wall. What about the case with tissue stuffed in between powder and bullet? This puts near twice as much powder closer to the flash hole. More powder gets ignited in those first few microseconds than a case half full of powder where half the powder's in the front half of the case body. Again, right on these, too. Probably with neck only sized cases. With my full length sized ones there's no noticable difference in the chrony tests I did. Never tested the diffference using neck only sizing. With the same load producing the same peak pressure, they all will expand to a perfect fit in the chamber, all will have the same case volume. New cases will spring back more than fired cases. The more times a case gets neck sized, the larger its body is after each firing, both in headspace and diameter. Proper full length sized cases don't do that. [/QUOTE]
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