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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Drag Function question.
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<blockquote data-quote="Jeff In TX" data-source="post: 32237" data-attributes="member: 1522"><p>TiroFijo </p><p></p><p>Brad's program at JBM uses a very massaged G1 drag model. Brad is extremely knowledgeable about ballistics. He used to have an outstanding ballistic program called JBM On Target but quit selling it back around 96/97 time frame. If you ask him, he will tell you that he uses the same calculations that have come out of Aberdeen proving grounds. When using his on-line program using the G1 drag function, it has been designed/massaged to match the G5 drag model and actual data for the bullets tested by the US Army. Which a lot of times has been the various sierra match king bullets.</p><p></p><p>Like Brent said, a lot of these programs use a G1 drag model, but many have different mathematical calculations/algorithms. I've talked with some of the designers of these programs. Basically they worked with a particular bullet and load they were shooting and came up with a mathematical calculation that matched their actual data very closely. Then they designed and published their program around that data. So if you shoot a bullet that closely resembles the one they used to design their program, you will do very well. But remember they call it a G1 drag function.</p><p></p><p>Common sense still says that a boat tail bullet, a VLD bullet, flat base spire point and a flat nosed bullets will all have very different aerodynamic flight characteristics at ranges from 400 to 1500 yards. Using a single mathematical calculation designed around one drag model to calculate the exterior ballistic of all those different bullet types is a receipt for failure. </p><p></p><p>Those of us who are serious about long range shooting spent a lot of time shooting at long ranges. We also keep a very accurate logbook with all of our shooting data. Once you have that, it makes it easy to apply those numbers to a computer ballistic program and if necessary play with your data inputs so that you can closely match your actual data.</p></blockquote><p></p>
[QUOTE="Jeff In TX, post: 32237, member: 1522"] TiroFijo Brad's program at JBM uses a very massaged G1 drag model. Brad is extremely knowledgeable about ballistics. He used to have an outstanding ballistic program called JBM On Target but quit selling it back around 96/97 time frame. If you ask him, he will tell you that he uses the same calculations that have come out of Aberdeen proving grounds. When using his on-line program using the G1 drag function, it has been designed/massaged to match the G5 drag model and actual data for the bullets tested by the US Army. Which a lot of times has been the various sierra match king bullets. Like Brent said, a lot of these programs use a G1 drag model, but many have different mathematical calculations/algorithms. I’ve talked with some of the designers of these programs. Basically they worked with a particular bullet and load they were shooting and came up with a mathematical calculation that matched their actual data very closely. Then they designed and published their program around that data. So if you shoot a bullet that closely resembles the one they used to design their program, you will do very well. But remember they call it a G1 drag function. Common sense still says that a boat tail bullet, a VLD bullet, flat base spire point and a flat nosed bullets will all have very different aerodynamic flight characteristics at ranges from 400 to 1500 yards. Using a single mathematical calculation designed around one drag model to calculate the exterior ballistic of all those different bullet types is a receipt for failure. Those of us who are serious about long range shooting spent a lot of time shooting at long ranges. We also keep a very accurate logbook with all of our shooting data. Once you have that, it makes it easy to apply those numbers to a computer ballistic program and if necessary play with your data inputs so that you can closely match your actual data. [/QUOTE]
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Drag Function question.
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