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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Experiment for quantifying lot to lot variations of powders
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<blockquote data-quote="Michael Courtney" data-source="post: 682919" data-attributes="member: 28191"><p>We are ballistics professionals. We have strain based systems, including the PressureTraceII. We also have PZT-based pressure measurement systems. Pressure measurements would be more appropriate if the intent of the study was focused on the safety aspects of lot-to-lot variations. We're expecting the average velocity and pressure variations to typically be from 1 to 3% from lot to lot. With careful reloading procedures, lot to lot variations would be unlikely to present safety issues unless they were 5-10%. Also, our experience with the PressureTrace II system suggests that typical accuracy expectations are on the order of 2-3%. Experiments are especially challenging when the measurement uncertainty is about the same size as the expected effect being studied, maybe larger. </p><p></p><p>The focus of the study is on velocity variations that would be of concern to precision long range shooting. Our LED-based chronographs are capable of 0.1% accuracy when calibrated immediately prior to use. It's hard to see what would be added by pressure measurements only accurate to 2-3%, when the precision of our chronographs allows us to see the variations under study, but the pressure measurements do not. </p><p></p><p>Chronograph based studies also cost a lot less in terms of prep and are much faster in terms of range time. 50 shots per hour is typical. Pressure-based studies are much more expensive and time consuming, and while some shooters are wowed by the graphs of pressure curves, I'll take reliable velocity data over pressure data of quality that is marginal for the intended purpose. </p><p></p><p>Don't get me wrong, PressureTrace II is great for its intended purposes, many of which are discussed at the web site:</p><p></p><p><a href="http://www.shootingsoftware.com/pressure.htm" target="_blank">RSI - PressureTrace</a></p><p></p><p>I just don't see what it would add to this study.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 682919, member: 28191"] We are ballistics professionals. We have strain based systems, including the PressureTraceII. We also have PZT-based pressure measurement systems. Pressure measurements would be more appropriate if the intent of the study was focused on the safety aspects of lot-to-lot variations. We're expecting the average velocity and pressure variations to typically be from 1 to 3% from lot to lot. With careful reloading procedures, lot to lot variations would be unlikely to present safety issues unless they were 5-10%. Also, our experience with the PressureTrace II system suggests that typical accuracy expectations are on the order of 2-3%. Experiments are especially challenging when the measurement uncertainty is about the same size as the expected effect being studied, maybe larger. The focus of the study is on velocity variations that would be of concern to precision long range shooting. Our LED-based chronographs are capable of 0.1% accuracy when calibrated immediately prior to use. It's hard to see what would be added by pressure measurements only accurate to 2-3%, when the precision of our chronographs allows us to see the variations under study, but the pressure measurements do not. Chronograph based studies also cost a lot less in terms of prep and are much faster in terms of range time. 50 shots per hour is typical. Pressure-based studies are much more expensive and time consuming, and while some shooters are wowed by the graphs of pressure curves, I'll take reliable velocity data over pressure data of quality that is marginal for the intended purpose. Don't get me wrong, PressureTrace II is great for its intended purposes, many of which are discussed at the web site: [url=http://www.shootingsoftware.com/pressure.htm]RSI - PressureTrace[/url] I just don't see what it would add to this study. [/QUOTE]
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Experiment for quantifying lot to lot variations of powders
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