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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Cooper Rifles and Max Loads
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<blockquote data-quote="Mikecr" data-source="post: 2105797" data-attributes="member: 1521"><p>No, that's a shade tree overbore index normalized using '500'. The overbore index is useful comparatively only for predicting barrel life.</p><p></p><p>QL weighting factor functionally defines a bottlenecking attribute of a given cartridge. A rough ratio of how much powder burns in a chamber -vs- further down a bore. QL needs it to assume a certain mass of unburned powder will travel with the bullet as a slug (of added mass).</p><p></p><p>Think powder funnel; Which cartridge designs efficiently pass powder down bores, and which hold back on that powder.</p><p>A WSSM holds powder back to be burned in the chamber, while a 30-06 adds to bullet mass with a great big slug of yet unburned powder against the back of bullets. This slug then flashes at the muzzle, creating a big pressure spike all the way back to the chamber.</p><p>The WSSM/WSM cases, set to any capacity, can prove more efficient than .473 case head cartridges of same capacities.</p><p></p><p>Most .473 case head cartridges of 243win capacity or higher are ~.5, with higher bottlenecking designs dropping the number. </p><p>A 6mmRem does not drop the number lower, but actually raises it, as the case body is even longer than 243Win, and there is high body taper, and still a low shoulder angle(even while not quite as low).</p><p></p><p>This bottlenecking, is also absent in underbores like 30br/6PPC, which is why they reward so much for fastest powders and extreme starting pressure conditions. Without that, much of the powder would just follow the bullet, burning inconsistently later down the bore,, and so much for competitive.</p><p></p><p>Anyway, you should set weighting factor around 0.55 and recalibrate.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 2105797, member: 1521"] No, that's a shade tree overbore index normalized using '500'. The overbore index is useful comparatively only for predicting barrel life. QL weighting factor functionally defines a bottlenecking attribute of a given cartridge. A rough ratio of how much powder burns in a chamber -vs- further down a bore. QL needs it to assume a certain mass of unburned powder will travel with the bullet as a slug (of added mass). Think powder funnel; Which cartridge designs efficiently pass powder down bores, and which hold back on that powder. A WSSM holds powder back to be burned in the chamber, while a 30-06 adds to bullet mass with a great big slug of yet unburned powder against the back of bullets. This slug then flashes at the muzzle, creating a big pressure spike all the way back to the chamber. The WSSM/WSM cases, set to any capacity, can prove more efficient than .473 case head cartridges of same capacities. Most .473 case head cartridges of 243win capacity or higher are ~.5, with higher bottlenecking designs dropping the number. A 6mmRem does not drop the number lower, but actually raises it, as the case body is even longer than 243Win, and there is high body taper, and still a low shoulder angle(even while not quite as low). This bottlenecking, is also absent in underbores like 30br/6PPC, which is why they reward so much for fastest powders and extreme starting pressure conditions. Without that, much of the powder would just follow the bullet, burning inconsistently later down the bore,, and so much for competitive. Anyway, you should set weighting factor around 0.55 and recalibrate. [/QUOTE]
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