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Rifles, Reloading, Optics, Equipment
Reloading
Accurate Burn Rate chart that compares Hodgden-Alliant-Viht powders
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<blockquote data-quote="Veteran" data-source="post: 2430625" data-attributes="member: 118038"><p>Here's a graph of velocity vs. charge weight for N565 in a 338 LM</p><p></p><p>[ATTACH=full]337932[/ATTACH]</p><p></p><p>Now using the actual velocities from chronograph and putting them in the QL model to back calculate burn rate one can look at burn rate over charge weight and pressure changes over time as charge weight goes up.</p><p></p><p>[ATTACH=full]337938[/ATTACH]</p><p></p><p>Here's the graph of burn rate vs. charge weight which in shape closely mirrors the velocity chart as expected.</p><p>What I like to do is then average the burn rates from these data, and use the new average as my "burn rate" </p><p>for my specific rifle and my specific bullet, and my specific cartridge. I use this new derived burn rate to then model </p><p>all my future loads with that same rig, and bullet weight, and cartridge. Its pretty accurate. </p><p></p><p>So, these graphs are from about a year ago. I certainly understand burn rate is not a constant. I understand well it varies with </p><p>many many things. But, I hope I know how to use the information I have to be a better reloader and shooter too.</p><p></p><p>In some of this work, it is also interesting that when I look for the velocity nodes and flat spots, and I graph MOA along with </p><p>velocity and burn rate, the lower MOA's often match the velocity node flat spots which the burn rate chart will mirror too.</p><p></p><p>Just interesting stuff. But this is why I like working with the numbers out of QL to rank my powders, and not the charts.</p><p></p><p>By the way, QL shows the burn rate of N565 is supposed to be .3109 in a .338 LM. My chart shows that in my rifle with </p><p>26 inch bbl. shooting 250 gr. bullets at these charge weights its actually .3506. So that demonstrates burn rate is not constant</p><p>and does vary by cartridge, by rifle, by charge weight/density of load, etc. Its all pressure, volume, temperature law related.</p><p>PVT analysis 101. But again, we need a starting point, a way to rank things as a start. Gotta make some comprimises somewhere just to get out of bed in the morning! Then you can get your nose in it and fine tune!</p><p></p><p></p><p><img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite1" alt=":)" title="Smile :)" loading="lazy" data-shortname=":)" /></p></blockquote><p></p>
[QUOTE="Veteran, post: 2430625, member: 118038"] Here's a graph of velocity vs. charge weight for N565 in a 338 LM [ATTACH type="full"]337932[/ATTACH] Now using the actual velocities from chronograph and putting them in the QL model to back calculate burn rate one can look at burn rate over charge weight and pressure changes over time as charge weight goes up. [ATTACH type="full"]337938[/ATTACH] Here's the graph of burn rate vs. charge weight which in shape closely mirrors the velocity chart as expected. What I like to do is then average the burn rates from these data, and use the new average as my "burn rate" for my specific rifle and my specific bullet, and my specific cartridge. I use this new derived burn rate to then model all my future loads with that same rig, and bullet weight, and cartridge. Its pretty accurate. So, these graphs are from about a year ago. I certainly understand burn rate is not a constant. I understand well it varies with many many things. But, I hope I know how to use the information I have to be a better reloader and shooter too. In some of this work, it is also interesting that when I look for the velocity nodes and flat spots, and I graph MOA along with velocity and burn rate, the lower MOA's often match the velocity node flat spots which the burn rate chart will mirror too. Just interesting stuff. But this is why I like working with the numbers out of QL to rank my powders, and not the charts. By the way, QL shows the burn rate of N565 is supposed to be .3109 in a .338 LM. My chart shows that in my rifle with 26 inch bbl. shooting 250 gr. bullets at these charge weights its actually .3506. So that demonstrates burn rate is not constant and does vary by cartridge, by rifle, by charge weight/density of load, etc. Its all pressure, volume, temperature law related. PVT analysis 101. But again, we need a starting point, a way to rank things as a start. Gotta make some comprimises somewhere just to get out of bed in the morning! Then you can get your nose in it and fine tune! :) [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Accurate Burn Rate chart that compares Hodgden-Alliant-Viht powders
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