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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: 2429675" data-attributes="member: 118038"><p>Dont you know Its all RELATIVE?</p><p>Its as relative as it can be with as I said a "somewhat" consistent pressure bomb testing method that is not exactly the same from powder co. to powder co. Its not exact. I agree with you that powders from one chart to the next switch places sometimes and that can be very misleading and frustrating......I agree with you that</p><p>changes in cartridge size (volume)</p><p>and bullet weight( a proxy for pressure) and even the temperature in the pressure bomb or the cartridge/ chamber will cause changes to the burn rate.</p><p>Charts are for rough granularity of sorting only. US 869 is always gonna be slower than H4895 under any practical set of temperature, and pressure and volume conditions.</p><p></p><p>I suppose in the PVT equations you might find some very extreme boundary condition where its not so, but it would be an artificially created circumstance, not encountered in the real world usual range of expected boundary conditions.</p><p>On a rough relative stack, 4895 is always faster than US 869.</p><p></p><p>So, I dont like using the charts as much as I like using the values from QL. The designers of QL as explained by Chris Long in his white paper have tried to look at all the burn rate information supplied by manufacturers and users and true it in the software to get more accurate predictions.</p><p></p><p>QL also adjusts the starting burn rate input for specific pressure, and temperature inputs to model the actual conditions. It also accounts for the volume of every cartridge used measured by water weight, and it of course accounts for bullet weight and barrel friction, even seating depth.</p><p></p><p>But you have to start some place.</p><p>The initial model inputs are not perfect. QL did not get samples of all the powders and run a lab bomb test on all of them side by side under identical conditions.</p><p></p><p>But their numbers are as close as you can get. Not exact, not perfect, but darn close. A relative ranking of their model inputs for burn rates is the best "relative ranking" that I know of. Perhaps the DOD or someone else has some data that is non public, but no one has access.</p><p></p><p>If I have mis stated anything, it was not that I mis stated that the powders are RELATIVE to one another in their burn rates. They are.</p><p></p><p>Where I may have mis stated is in even considering that there is ever an ABSOLUTE value for any burn rate.</p><p></p><p>PVT conditions can occur in any mix and any combination meaning the absolute value of the burn rate can be almost anything depending on a range of values and permutations of pressure, volume, and temperature.</p><p></p><p>But, if we try to stay within some normally expected range of boundary conditions, there is a more narrow range or standard deviation of "psuedo absolute"</p><p>values for burn rate we can talk about. And then if we rank these on a relative basis, we have our RELATIVE stack.</p><p></p><p>So thats what I believe about relativity.....Its all relative.</p></blockquote><p></p>
[QUOTE="Veteran, post: 2429675, member: 118038"] Dont you know Its all RELATIVE? Its as relative as it can be with as I said a "somewhat" consistent pressure bomb testing method that is not exactly the same from powder co. to powder co. Its not exact. I agree with you that powders from one chart to the next switch places sometimes and that can be very misleading and frustrating......I agree with you that changes in cartridge size (volume) and bullet weight( a proxy for pressure) and even the temperature in the pressure bomb or the cartridge/ chamber will cause changes to the burn rate. Charts are for rough granularity of sorting only. US 869 is always gonna be slower than H4895 under any practical set of temperature, and pressure and volume conditions. I suppose in the PVT equations you might find some very extreme boundary condition where its not so, but it would be an artificially created circumstance, not encountered in the real world usual range of expected boundary conditions. On a rough relative stack, 4895 is always faster than US 869. So, I dont like using the charts as much as I like using the values from QL. The designers of QL as explained by Chris Long in his white paper have tried to look at all the burn rate information supplied by manufacturers and users and true it in the software to get more accurate predictions. QL also adjusts the starting burn rate input for specific pressure, and temperature inputs to model the actual conditions. It also accounts for the volume of every cartridge used measured by water weight, and it of course accounts for bullet weight and barrel friction, even seating depth. But you have to start some place. The initial model inputs are not perfect. QL did not get samples of all the powders and run a lab bomb test on all of them side by side under identical conditions. But their numbers are as close as you can get. Not exact, not perfect, but darn close. A relative ranking of their model inputs for burn rates is the best "relative ranking" that I know of. Perhaps the DOD or someone else has some data that is non public, but no one has access. If I have mis stated anything, it was not that I mis stated that the powders are RELATIVE to one another in their burn rates. They are. Where I may have mis stated is in even considering that there is ever an ABSOLUTE value for any burn rate. PVT conditions can occur in any mix and any combination meaning the absolute value of the burn rate can be almost anything depending on a range of values and permutations of pressure, volume, and temperature. But, if we try to stay within some normally expected range of boundary conditions, there is a more narrow range or standard deviation of "psuedo absolute" values for burn rate we can talk about. And then if we rank these on a relative basis, we have our RELATIVE stack. So thats what I believe about relativity.....Its all relative. [/QUOTE]
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Accurate Burn Rate chart that compares Hodgden-Alliant-Viht powders
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