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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Drag Function question.
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<blockquote data-quote="TiroFijo" data-source="post: 32233" data-attributes="member: 974"><p>Jeff, check what Sierra says, they do test their own bullets at several velocity ranges, and particularly the BCs or their bullets used by the US armed forces (such as the .308" 175 and 190 SMK) were extensively tested with doppler radars:</p><p> <a href="http://www.exteriorballistics.com/ebexplained/5th/24.cfm" target="_blank">http://www.exteriorballistics.com/ebexplained/5th/24.cfm</a> </p><p></p><p>"The G1 drag function is the best standard drag model to use. We have tested several drag functions (G1 for sporting bullets; GL for lead bullets; G5 for boat tail bullets; and G6 for flat base, sharp pointed, fully jacketed bullets). For each drag function we have measured BC values referenced to that function and observed how those BC values change with bullet velocity. We have chosen G1 because the changes in BC values with bullet velocity are least, and because there is a vast database in the literature on BC values referenced to the G1 standard. Also, to our knowledge all projectile manufacturers refer their published BC values to the G1 drag function, which facilitates comparisons among bullets of different calibers, weights, shapes and manufacturers."</p><p></p><p>BTW, a 300 WM firing a 190 SMK @ 3000 fps, std. cond., goes below 1600 fps at 920 yds. And you won't get a better BC match with ANY drag function than the 3.4% I just mentioned.</p><p></p><p>In my experience the Infinity trajectory predictions are spot on up to 1000 yds.</p><p></p><p>Of course for other makers choose the drag funtion that theoretically should fit best, but don't expect a perfect fit.</p><p></p><p>[ 03-07-2004: Message edited by: TiroFijo ]</p></blockquote><p></p>
[QUOTE="TiroFijo, post: 32233, member: 974"] Jeff, check what Sierra says, they do test their own bullets at several velocity ranges, and particularly the BCs or their bullets used by the US armed forces (such as the .308" 175 and 190 SMK) were extensively tested with doppler radars: [url="http://www.exteriorballistics.com/ebexplained/5th/24.cfm"]http://www.exteriorballistics.com/ebexplained/5th/24.cfm[/url] "The G1 drag function is the best standard drag model to use. We have tested several drag functions (G1 for sporting bullets; GL for lead bullets; G5 for boat tail bullets; and G6 for flat base, sharp pointed, fully jacketed bullets). For each drag function we have measured BC values referenced to that function and observed how those BC values change with bullet velocity. We have chosen G1 because the changes in BC values with bullet velocity are least, and because there is a vast database in the literature on BC values referenced to the G1 standard. Also, to our knowledge all projectile manufacturers refer their published BC values to the G1 drag function, which facilitates comparisons among bullets of different calibers, weights, shapes and manufacturers." BTW, a 300 WM firing a 190 SMK @ 3000 fps, std. cond., goes below 1600 fps at 920 yds. And you won't get a better BC match with ANY drag function than the 3.4% I just mentioned. In my experience the Infinity trajectory predictions are spot on up to 1000 yds. Of course for other makers choose the drag funtion that theoretically should fit best, but don't expect a perfect fit. [ 03-07-2004: Message edited by: TiroFijo ] [/QUOTE]
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