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Rifles, Reloading, Optics, Equipment
Reloading
procedure for measuring case volume
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<blockquote data-quote="Bart B" data-source="post: 635458" data-attributes="member: 5302"><p>For me, the best measure of case volume is case weight. I think case volume is best measured when the case walls are pressed hard against the chamber walls and bolt face; that's when the case outside dimensions are exactly the same for each case. And that's also when chamber pressure is at its peak. Otherwise, the normal varables in outside case measurements will effect the space inside of the case. While there may be very small differences in muzzle velocity in cases sized to different dimensions, I don't think they're enough to matter. And the only way to measure them accurately is with the rifle clamped in a machine rest free from a human's inconsistant ability to hold the rifle into their bodies the same way for each shot.</p><p></p><p>Do this for a detailed result:</p><p></p><p>1. Calculate the chamber volume in cubic inches with simple high school math formulas for cones. You might need a chamber case to get the dimensions. Otherwise, use SAAMI's chamber drawings for reference; they're close enough for factory rifles.</p><p></p><p>2. Multiply the chamber volume in cubic inches by 1597; a cubic inch of cartridge brass (70% brass and 30% zinc) weighs 1597 grains.</p><p></p><p>3. Weigh cases to the nearest 1/10th grain.</p><p></p><p>4. Subtract case weight from chamber volume weight in brass; the answer is case volume in brass weight.</p><p></p><p>5. Divide case volume weight in brass by 1597 and the answer is case volume in cubic inches.</p><p></p><p>(I think I did the above right..........)</p><p></p><p>Why is case volume important to you?</p></blockquote><p></p>
[QUOTE="Bart B, post: 635458, member: 5302"] For me, the best measure of case volume is case weight. I think case volume is best measured when the case walls are pressed hard against the chamber walls and bolt face; that's when the case outside dimensions are exactly the same for each case. And that's also when chamber pressure is at its peak. Otherwise, the normal varables in outside case measurements will effect the space inside of the case. While there may be very small differences in muzzle velocity in cases sized to different dimensions, I don't think they're enough to matter. And the only way to measure them accurately is with the rifle clamped in a machine rest free from a human's inconsistant ability to hold the rifle into their bodies the same way for each shot. Do this for a detailed result: 1. Calculate the chamber volume in cubic inches with simple high school math formulas for cones. You might need a chamber case to get the dimensions. Otherwise, use SAAMI's chamber drawings for reference; they're close enough for factory rifles. 2. Multiply the chamber volume in cubic inches by 1597; a cubic inch of cartridge brass (70% brass and 30% zinc) weighs 1597 grains. 3. Weigh cases to the nearest 1/10th grain. 4. Subtract case weight from chamber volume weight in brass; the answer is case volume in brass weight. 5. Divide case volume weight in brass by 1597 and the answer is case volume in cubic inches. (I think I did the above right..........) Why is case volume important to you? [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
procedure for measuring case volume
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