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Rifles, Reloading, Optics, Equipment
Reloading
Brass weight... How important?
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<blockquote data-quote="Mikecr" data-source="post: 1630256" data-attributes="member: 1521"><p>It is a lot harder to match and mange capacities than weighing cases and assuming everything else away. My earlier appeal to extremes was to illustrate that brass weight and brass shape <em>can be</em> totally different.</p><p>We form our cases to shape, which along with thickness and build affects capacity. And thickness also affects our ability to form to shape. Same with hardness, and sizing types/amounts.</p><p>This matters as initial confinement and initial expansion forces affect powder burn rate, pressure peaks and barrel timing.</p><p></p><p>In my experience, a capacity manged to match does not follow brass weight directly.</p><p>It would be nice if it did. But with some lots of brass there ends up being a good correlation, and not so much with other lots..</p><p>I just can't know it until forming and testing to see it, so where motivated to do so, I go ahead and do that.</p><p></p><p>With a past cartridge I started with 1,000 new cases of same lot.</p><p>I did weigh them and the weights were all over hell.. So I could cut all primer pockets to same depths, and trim all cases to same (wrong) length, and separate them into many groups or just biggest group by thickness (as measured at necks), and weight variance would probably be lowered. But my objective is not weight matching, it's capacity matching, with other matching attributes as well.</p><p></p><p>I chose to sort by thickness, and thickness variance to begin.</p><p>This quickly whittled me down to ~140 cases at same thickness, no variance.</p><p>I then cut pockets, turned necks to desired thickness, fire-formed 3 times with no sizing, trimmed cases to same (correct) length, measured H20 capacities.</p><p>This took me down to ~80 cases matching in everything, including capacity.</p><p>A lot of effort, a lot of waste, but direct.</p><p></p><p>For the hell of it I weighed all prepped, formed, matching and deviants of the 140 cases. There was a mean weight with reasonable variances, and what I found was that I could not pick out 80 capacity matching from deviants -by weight.</p><p>Out of 1,000, the only contribution weight measure provided for me was in finding 2 cases with missing flash holes and a retarded/liberal extraction groove.</p><p></p><p>On the 'waste', the ~860 culled cases,, I eventually sold them off at 3x what I paid for them. I've gone through 3 barrels with those same 80 cases, never needed further trimming, and you can bet they still match in capacity. They will last the rest of my life, just like this.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 1630256, member: 1521"] It is a lot harder to match and mange capacities than weighing cases and assuming everything else away. My earlier appeal to extremes was to illustrate that brass weight and brass shape [I]can be[/I] totally different. We form our cases to shape, which along with thickness and build affects capacity. And thickness also affects our ability to form to shape. Same with hardness, and sizing types/amounts. This matters as initial confinement and initial expansion forces affect powder burn rate, pressure peaks and barrel timing. In my experience, a capacity manged to match does not follow brass weight directly. It would be nice if it did. But with some lots of brass there ends up being a good correlation, and not so much with other lots.. I just can't know it until forming and testing to see it, so where motivated to do so, I go ahead and do that. With a past cartridge I started with 1,000 new cases of same lot. I did weigh them and the weights were all over hell.. So I could cut all primer pockets to same depths, and trim all cases to same (wrong) length, and separate them into many groups or just biggest group by thickness (as measured at necks), and weight variance would probably be lowered. But my objective is not weight matching, it's capacity matching, with other matching attributes as well. I chose to sort by thickness, and thickness variance to begin. This quickly whittled me down to ~140 cases at same thickness, no variance. I then cut pockets, turned necks to desired thickness, fire-formed 3 times with no sizing, trimmed cases to same (correct) length, measured H20 capacities. This took me down to ~80 cases matching in everything, including capacity. A lot of effort, a lot of waste, but direct. For the hell of it I weighed all prepped, formed, matching and deviants of the 140 cases. There was a mean weight with reasonable variances, and what I found was that I could not pick out 80 capacity matching from deviants -by weight. Out of 1,000, the only contribution weight measure provided for me was in finding 2 cases with missing flash holes and a retarded/liberal extraction groove. On the 'waste', the ~860 culled cases,, I eventually sold them off at 3x what I paid for them. I've gone through 3 barrels with those same 80 cases, never needed further trimming, and you can bet they still match in capacity. They will last the rest of my life, just like this. [/QUOTE]
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Brass weight... How important?
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