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Rifles, Reloading, Optics, Equipment
Reloading
QL and why or GRT
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<blockquote data-quote="RegionRat" data-source="post: 2715255" data-attributes="member: 57231"><p>The issues folks are having are not difficult to explain, but that said they are difficult to solve.</p><p></p><p>There are several other issues with matching results that are not as popular to discuss. It is easy to grab an accurate muzzle velocity but how many folks can (calibrate and) measure pressure?</p><p></p><p>Clearly the BA and energy from the powder charge is important, but the energy of the primer, energy lost to the case/chamber fit, energy lost due to brass prep, combustion pressure effects of jump and bullet engraving, bullet friction, etc, etc,. are also significant parts of the system. </p><p></p><p>Many folks take this on with the idea that they can use one or two levers to fit the model to their data, but then try to extrapolate parts of their model to a different recipe or even to a different gun, and they try this without actual pressure data. The models can swallow some composite errors where it comes to friction losses, but not knowing the actual pressure is a handicap if you then try to extrapolate using the models. </p><p></p><p>With those concepts in mind, it shouldn't be a surprise that the odds of a perfect match to all those other parameters coming from the defaults in the software, versus your results, probably won't be perfect even when you have decent input for most of them since it is rare to have all of them.</p><p></p><p>That is not to be taken as a condemnation of the programs or those efforts versus their value. Even without pressure and other measurement inputs, you can learn a lot from practicing with these models.</p><p></p><p>The research, measurements, and experience required to just run a "standard" scenario is not bad. However, the experience required to actually predict pressure and match results when jumping to say a wildcat prototype is another matter. In my opinion a person will need to study and practice with many different "standard" load cases, calibers, and rifle systems before they get to where they can extrapolate well with big changes, unusual cases, or wildcats. YMMV</p></blockquote><p></p>
[QUOTE="RegionRat, post: 2715255, member: 57231"] The issues folks are having are not difficult to explain, but that said they are difficult to solve. There are several other issues with matching results that are not as popular to discuss. It is easy to grab an accurate muzzle velocity but how many folks can (calibrate and) measure pressure? Clearly the BA and energy from the powder charge is important, but the energy of the primer, energy lost to the case/chamber fit, energy lost due to brass prep, combustion pressure effects of jump and bullet engraving, bullet friction, etc, etc,. are also significant parts of the system. Many folks take this on with the idea that they can use one or two levers to fit the model to their data, but then try to extrapolate parts of their model to a different recipe or even to a different gun, and they try this without actual pressure data. The models can swallow some composite errors where it comes to friction losses, but not knowing the actual pressure is a handicap if you then try to extrapolate using the models. With those concepts in mind, it shouldn't be a surprise that the odds of a perfect match to all those other parameters coming from the defaults in the software, versus your results, probably won't be perfect even when you have decent input for most of them since it is rare to have all of them. That is not to be taken as a condemnation of the programs or those efforts versus their value. Even without pressure and other measurement inputs, you can learn a lot from practicing with these models. The research, measurements, and experience required to just run a "standard" scenario is not bad. However, the experience required to actually predict pressure and match results when jumping to say a wildcat prototype is another matter. In my opinion a person will need to study and practice with many different "standard" load cases, calibers, and rifle systems before they get to where they can extrapolate well with big changes, unusual cases, or wildcats. YMMV [/QUOTE]
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Reloading
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