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Rifles, Reloading, Optics, Equipment
Reloading
brass weight sorting
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<blockquote data-quote="Bart B" data-source="post: 560750" data-attributes="member: 5302"><p>If case capacity was directly related to pressure, velocity and "tune" (musical notes?), then my tests years ago using new unfired and neck sized twice fired cases would not have produced their groups at 1000 yards atop each other. Muzzle velocity would have been different and therefore, so would bullet drop. The only difference was accuracy with new cases was much better.</p><p></p><p>Note that a 30 caliber bullet needing 40 pounds of force to push it out of the case gets pushed out when pressure inside the case is about 530 psi. Most handloaded cases have that amount or less; mine are much less. And the case is pressed against the chamber at only 1000 psi. So I don't see any way how case capacity at primer ignition has any significant effect on peak pressure and/or velocity. Show me strain gage time vs. pressure/velocity curves with different case capacities at primer detonation that prove it and I'll change my mind.</p><p></p><p>The above aside, this is a most interesting discussion.</p><p></p><p>If case capacity at primer detonation has to equal across all cases for all shots to have the same pressure curve shapes, consider this. Neck only sizing is well known to require cases be full length resized after several firings. Those cases get bigger each firing. They soon cause bolt binding. Their capacity increases with each firing. Maybe this is why so many top high power competitors get best accuracy full length sizing all the time. Virtually all high power matches are won with and records set with full length sized (or new) cases.</p></blockquote><p></p>
[QUOTE="Bart B, post: 560750, member: 5302"] If case capacity was directly related to pressure, velocity and "tune" (musical notes?), then my tests years ago using new unfired and neck sized twice fired cases would not have produced their groups at 1000 yards atop each other. Muzzle velocity would have been different and therefore, so would bullet drop. The only difference was accuracy with new cases was much better. Note that a 30 caliber bullet needing 40 pounds of force to push it out of the case gets pushed out when pressure inside the case is about 530 psi. Most handloaded cases have that amount or less; mine are much less. And the case is pressed against the chamber at only 1000 psi. So I don't see any way how case capacity at primer ignition has any significant effect on peak pressure and/or velocity. Show me strain gage time vs. pressure/velocity curves with different case capacities at primer detonation that prove it and I'll change my mind. The above aside, this is a most interesting discussion. If case capacity at primer detonation has to equal across all cases for all shots to have the same pressure curve shapes, consider this. Neck only sizing is well known to require cases be full length resized after several firings. Those cases get bigger each firing. They soon cause bolt binding. Their capacity increases with each firing. Maybe this is why so many top high power competitors get best accuracy full length sizing all the time. Virtually all high power matches are won with and records set with full length sized (or new) cases. [/QUOTE]
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