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Rifles, Reloading, Optics, Equipment
Reloading
Sorting Brass
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<blockquote data-quote="Unclenick" data-source="post: 2382226" data-attributes="member: 106107"><p>If you don't sort brass by headstamp, sorting by weight is not very useful unless the difference is extreme. I did an experiment with mixed 308 brass once. Based on cartridge brass being 8.53 times denser than 4°C water, I used the weight difference in a dozen cases to attempt to predict their differences in case water overflow capacity, and the prediction accuracy proved to be a wide ±20%. </p><p></p><p>The causes are several. One is that <a href="https://www.accurateshooter.com/technical-articles/x-ray-spectrometry-of-cartridge-brass/" target="_blank"><span style="color: rgb(41, 105, 176)">different manufacturers use different alloys</span></a>, and not just 70:30 copper:zinc brass (aka, cartridge brass, 260 brass, or C26000 brass). Remington, for example, uses 20:80 brass (8.67 times denser than water) and some have even used 40:60 brass (aka, Muntz metal, which is 8.34 times the density of water). But that's the minor contributor to the error. The main cause is that you can change things like rim thickness, extractor groove width and depth, and extractor groove relief angle values without changing the internal capacity of the case, and all these things have tolerances. If I walk a .308 case head from the lightest to the heaviest tolerance configuration, I get over 7 grains of weight difference without touching the internal capacity of the case. I haven't done the same thing for 223 brass, but, based on its weight and diameter, I would expect over half that difference to be applicable.</p><p></p><p>So, bottom line, sort by headstamp first, then by weight. Since most brass comes off multiple toolsets and the output is then mixed, this doesn't guarantee perfect uniformity; it just reduces the weight-related error to at least be using the same basic design. After that, look at load history, if you really want cases that were all treated the same.</p></blockquote><p></p>
[QUOTE="Unclenick, post: 2382226, member: 106107"] If you don't sort brass by headstamp, sorting by weight is not very useful unless the difference is extreme. I did an experiment with mixed 308 brass once. Based on cartridge brass being 8.53 times denser than 4°C water, I used the weight difference in a dozen cases to attempt to predict their differences in case water overflow capacity, and the prediction accuracy proved to be a wide ±20%. The causes are several. One is that [URL='https://www.accurateshooter.com/technical-articles/x-ray-spectrometry-of-cartridge-brass/'][COLOR=rgb(41, 105, 176)]different manufacturers use different alloys[/COLOR][/URL], and not just 70:30 copper:zinc brass (aka, cartridge brass, 260 brass, or C26000 brass). Remington, for example, uses 20:80 brass (8.67 times denser than water) and some have even used 40:60 brass (aka, Muntz metal, which is 8.34 times the density of water). But that's the minor contributor to the error. The main cause is that you can change things like rim thickness, extractor groove width and depth, and extractor groove relief angle values without changing the internal capacity of the case, and all these things have tolerances. If I walk a .308 case head from the lightest to the heaviest tolerance configuration, I get over 7 grains of weight difference without touching the internal capacity of the case. I haven't done the same thing for 223 brass, but, based on its weight and diameter, I would expect over half that difference to be applicable. So, bottom line, sort by headstamp first, then by weight. Since most brass comes off multiple toolsets and the output is then mixed, this doesn't guarantee perfect uniformity; it just reduces the weight-related error to at least be using the same basic design. After that, look at load history, if you really want cases that were all treated the same. [/QUOTE]
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