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Rifles, Reloading, Optics, Equipment
Reloading
Possible Pressure Signs with factory Loaded Ammo?
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<blockquote data-quote="Bill Johnson" data-source="post: 1076987" data-attributes="member: 84129"><p>Estimating pressure from fired cases/primers is a tricky business, but I have found reading the primers to be fairly indicative of high pressure. What's missing in your analysis is the condition of the primers on the first factory rounds. Note that on all the other primers that, while at the highest powder loading you got what appears to be some extrusion into the firing pin hole, that none of the fired primers flattened to the point that they filled the bevel on the primer pocket.</p><p></p><p> This is an example of that:</p><p></p><p><a href="http://s813.photobucket.com/user/Dollar_Bill_2009/media/dscn3326_zpssxjlct9b.jpg.html" target="_blank"><img src="http://i813.photobucket.com/albums/zz53/Dollar_Bill_2009/dscn3326_zpssxjlct9b.jpg" alt="" class="fr-fic fr-dii fr-draggable " style="" /></a></p><p> </p><p>Measuring case head expansion is tricky also. First promulgated by Ken Waters, if I recall correctly, you must use a factory round and measure the case head prior to firing and then after, using a micrometer capable of measuring to .0001". </p><p> </p><p>Typical amounts of expansion with lower pressure rounds, like the .30-30 Winchester, usually yield maximum pressures at .0003"-.0004" expansion. Modern cartridges, like the .223 Remington, will show maximum pressure at .0004"-.0005", while .308 Winchester, .270 Winchester, etc., typically yield .0005"-.0006" expansion at max pressure. Magnums, like the .300 Winchester Magnum, show maximums at .0006"-.0007" expansion, and should be measured on the belt. A reading of .001 is generally considered as over max pressure.</p><p> </p><p>All this must be taken into account, including the stiff bolt handle lift, to get a true indication of higher-then-normal pressures.</p></blockquote><p></p>
[QUOTE="Bill Johnson, post: 1076987, member: 84129"] Estimating pressure from fired cases/primers is a tricky business, but I have found reading the primers to be fairly indicative of high pressure. What's missing in your analysis is the condition of the primers on the first factory rounds. Note that on all the other primers that, while at the highest powder loading you got what appears to be some extrusion into the firing pin hole, that none of the fired primers flattened to the point that they filled the bevel on the primer pocket. This is an example of that: [URL=http://s813.photobucket.com/user/Dollar_Bill_2009/media/dscn3326_zpssxjlct9b.jpg.html][IMG]http://i813.photobucket.com/albums/zz53/Dollar_Bill_2009/dscn3326_zpssxjlct9b.jpg[/IMG][/URL] Measuring case head expansion is tricky also. First promulgated by Ken Waters, if I recall correctly, you must use a factory round and measure the case head prior to firing and then after, using a micrometer capable of measuring to .0001". Typical amounts of expansion with lower pressure rounds, like the .30-30 Winchester, usually yield maximum pressures at .0003"-.0004" expansion. Modern cartridges, like the .223 Remington, will show maximum pressure at .0004"-.0005", while .308 Winchester, .270 Winchester, etc., typically yield .0005"-.0006" expansion at max pressure. Magnums, like the .300 Winchester Magnum, show maximums at .0006”-.0007” expansion, and should be measured on the belt. A reading of .001 is generally considered as over max pressure. All this must be taken into account, including the stiff bolt handle lift, to get a true indication of higher-then-normal pressures. [/QUOTE]
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Possible Pressure Signs with factory Loaded Ammo?
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