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Rifles, Reloading, Optics, Equipment
Reloading
Sorting Brass by weight
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<blockquote data-quote="Bart B" data-source="post: 605381" data-attributes="member: 5302"><p>Yes. Here's why.</p><p></p><p>If you put a 1 cubic foot block of gold in a box that holds 4 cubic feet, there's only 3 cubic feet of volume left in the box. If the block of gold's only 0.9 cubic feet, there's 3.1 cubic feet still empty in the box.</p><p></p><p>The chamber has the same dimensions, and therefore volume, for every round fired. Cartridge brass is very homogenous; uniform in metal types distributed throughout it. So, the volume of the case brass itself, whether a cubic block of brass weighing 200 grains or a cartridge case of the same weight, is all the same. It subtracts from the chamber volume. And the case volume at peak pressure is what's inside the case with its walls pressed hard against the chamber. That's where it counts. And the case is pressed hard against the chamber wall when pressure in it is about 8000 psi; very early in the pressure curve.</p><p></p><p>Sort cases by weight, but only after they've been fired once then resized to their reloading dimensions. Otherwise, the small difference in actual new case interior volume may vary enough to cause a small difference in chamber pressure rise time and peak level.</p><p></p><p>A 1% spread in case weight's close enough. There's more variance in primer detonation flame levels and duration causing pressure and velocity changes than what all cases of exactly the same weight and volume will produce.</p></blockquote><p></p>
[QUOTE="Bart B, post: 605381, member: 5302"] Yes. Here's why. If you put a 1 cubic foot block of gold in a box that holds 4 cubic feet, there's only 3 cubic feet of volume left in the box. If the block of gold's only 0.9 cubic feet, there's 3.1 cubic feet still empty in the box. The chamber has the same dimensions, and therefore volume, for every round fired. Cartridge brass is very homogenous; uniform in metal types distributed throughout it. So, the volume of the case brass itself, whether a cubic block of brass weighing 200 grains or a cartridge case of the same weight, is all the same. It subtracts from the chamber volume. And the case volume at peak pressure is what's inside the case with its walls pressed hard against the chamber. That's where it counts. And the case is pressed hard against the chamber wall when pressure in it is about 8000 psi; very early in the pressure curve. Sort cases by weight, but only after they've been fired once then resized to their reloading dimensions. Otherwise, the small difference in actual new case interior volume may vary enough to cause a small difference in chamber pressure rise time and peak level. A 1% spread in case weight's close enough. There's more variance in primer detonation flame levels and duration causing pressure and velocity changes than what all cases of exactly the same weight and volume will produce. [/QUOTE]
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Reloading
Sorting Brass by weight
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