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Rifles, Reloading, Optics, Equipment
Reloading
Loaded ammo bullet runout???
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<blockquote data-quote="Bart B" data-source="post: 666086" data-attributes="member: 5302"><p>Check out the section in the following link that starts with: <em>Most top 6PPC competitors run their ammo at pretty high pressures. Such pressures demand that cases be full-length sized each time they are loaded. But the trick is sizing the case just enough to allow proper feeding/extraction and no more.</em></p><p></p><p><a href="http://www.6mmbr.com/gunweek041.html" target="_blank">Speedy's 6PPC -- The Art of Accuracy</a></p><p></p><p>It's all based on the fact that chambers or cases (sized or new) are perfectly round. When neck only sized, their body soon starts interfering with the chamber at the body-shoulder junction and the case no longer perfectly centers its shoulder in the chamber shoulder without interference. Bottleneck case bodies need be sized down no more than 1/4 to 1/2 of a percent of their diameters to prevent this interference. They center up front at the shoulcer perfectly when fired regardless of how much clearance there is around them. Measure some chambers and both fired and sized cases from them for roundness and you'll see they're not perfectly round. They're pretty close to within a thousandth or less for chambers and two thousandths for cases. The more uniform case wall thickness is in their body and shoulder area, the more uniformly round they'll be.</p><p></p><p>One good way to see the difference between fired cases' out of round as well as diameter differences is to drop them into a Wilson case holder used in their trimmers. The holder's reamed to fit the body pretty close, but depending on how a given case is oriented in the holder, it will come to rest at different depths. The smaller diameter ones and those whose out of roundness matches that of the hole in the holder will go in deeper than larger diameter ones and those with mismatched out of round points to the holder. Most folks are surprised in the differences across a batch of fired cases from the same chamber.</p></blockquote><p></p>
[QUOTE="Bart B, post: 666086, member: 5302"] Check out the section in the following link that starts with: [I]Most top 6PPC competitors run their ammo at pretty high pressures. Such pressures demand that cases be full-length sized each time they are loaded. But the trick is sizing the case just enough to allow proper feeding/extraction and no more.[/I] [url=http://www.6mmbr.com/gunweek041.html]Speedy's 6PPC -- The Art of Accuracy[/url] It's all based on the fact that chambers or cases (sized or new) are perfectly round. When neck only sized, their body soon starts interfering with the chamber at the body-shoulder junction and the case no longer perfectly centers its shoulder in the chamber shoulder without interference. Bottleneck case bodies need be sized down no more than 1/4 to 1/2 of a percent of their diameters to prevent this interference. They center up front at the shoulcer perfectly when fired regardless of how much clearance there is around them. Measure some chambers and both fired and sized cases from them for roundness and you'll see they're not perfectly round. They're pretty close to within a thousandth or less for chambers and two thousandths for cases. The more uniform case wall thickness is in their body and shoulder area, the more uniformly round they'll be. One good way to see the difference between fired cases' out of round as well as diameter differences is to drop them into a Wilson case holder used in their trimmers. The holder's reamed to fit the body pretty close, but depending on how a given case is oriented in the holder, it will come to rest at different depths. The smaller diameter ones and those whose out of roundness matches that of the hole in the holder will go in deeper than larger diameter ones and those with mismatched out of round points to the holder. Most folks are surprised in the differences across a batch of fired cases from the same chamber. [/QUOTE]
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Loaded ammo bullet runout???
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