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Rifles, Reloading, Optics, Equipment
Reloading
Case weight vs internal volume
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<blockquote data-quote="Kennibear" data-source="post: 963874" data-attributes="member: 51650"><p>This thread has fascinated me for many reasons but the experience all have shared is priceless!</p><p></p><p>Couple of observations:</p><p></p><p>1) The case head has an extractor groove and if there is the slightest variation in uniformity of the groove case to case that will toss the volume of cases of the same weight off.</p><p></p><p>2) Brass springback is not uniform. Think about how much effort is put into the case neck (annealing, turning etc.) to make bullet release uniform. Does anybody do the same for the case body? I submit that fire formed or full length sized there is case dimensional differences from the same lot of cases after sizing or fire forming because of slight tolerances in case hardness. This has to show up in the H2O weight. Very small case diameter variations would drive the H2O volume off measurably.</p><p></p><p>3) From my Honors Chemistry class at San Jose State I remember the time spent teaching us how to fill and read the graduated cylinders by reading the meniscus. Even the room temp made a difference when you work to an overall accuracy of 0.1%. Did you fill the cases until they were flat across the neck or was there a slight convex hump of water surface tension?</p><p></p><p>I personally used to weight sort cases of the same lot. They didn't shoot noticeably better than random batches from the same lot but "it couldn't hurt". But after this thread I am really facing a conundrum. </p><p></p><p>KB</p></blockquote><p></p>
[QUOTE="Kennibear, post: 963874, member: 51650"] This thread has fascinated me for many reasons but the experience all have shared is priceless! Couple of observations: 1) The case head has an extractor groove and if there is the slightest variation in uniformity of the groove case to case that will toss the volume of cases of the same weight off. 2) Brass springback is not uniform. Think about how much effort is put into the case neck (annealing, turning etc.) to make bullet release uniform. Does anybody do the same for the case body? I submit that fire formed or full length sized there is case dimensional differences from the same lot of cases after sizing or fire forming because of slight tolerances in case hardness. This has to show up in the H2O weight. Very small case diameter variations would drive the H2O volume off measurably. 3) From my Honors Chemistry class at San Jose State I remember the time spent teaching us how to fill and read the graduated cylinders by reading the meniscus. Even the room temp made a difference when you work to an overall accuracy of 0.1%. Did you fill the cases until they were flat across the neck or was there a slight convex hump of water surface tension? I personally used to weight sort cases of the same lot. They didn't shoot noticeably better than random batches from the same lot but "it couldn't hurt". But after this thread I am really facing a conundrum. KB [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Case weight vs internal volume
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