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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
How to check a Chronograph?
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<blockquote data-quote="TexasHunter" data-source="post: 566361" data-attributes="member: 26082"><p>Wile,</p><p></p><p>Don't know what your calcs were but here's what my calculator gave me.</p><p></p><p>Berger 7mm / 168 / G7 BC = .316 / 3030 fps / sight height 2"</p><p></p><p>DA=1000, 300yds=2.9moa, 400yds=5.0moa, 500yds=7.4moa, coriolis off</p><p></p><p>DA=2000, 300yds=2.9moa, 400yds=5.0moa, 500yds=7.3moa, coriolis off</p><p></p><p>DA=3000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.3moa, coriolis off</p><p></p><p>DA=4000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.2moa, coriolis off</p><p></p><p>DA=5000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.2moa, coriolis off</p><p></p><p>DA=5000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.1moa, coriolis on @ 90º</p><p></p><p>In general, Berger BCs seem to be the most accurate of the different makers. Using 3255 fps drops the 500 yd dope to 5.9 moa with coriolis on at 5000 DA. I stopped at 5000' DA but that doesn't mean you weren't shooting in a much higher DA. I shot a match in OK back in Sept where the actual altitude was 1200'. When we started at 8am the actual DA was 2100' and by the time we finished at 4pm, the DA was almost 5000'. We were shooting east on every stage and back at the range HQ after the match several guys were complaining about their dope being too high out at 1000 yds toward the end of the match. I asked if they input DA and they said "sure we did, this morning". When they re-measured and re-input while we stood there, they were ****ed that they hadn't considered the massive change as the day warmed up. There is also the possibility that different bore / groove configurations have varying effects on the actual BC but it would have to be huge to change the 500 yd dope by 1.2 moa so not a very likely culprit. Head and tail winds can also effect elevation to some degree but again not this much this close.</p><p></p><p>Bottom line is that I personally fought this issue for years and until my wife gave me a Kestral 4500 last Christmas and I was able to measure and input DA directly, I never had confidence in my calculations. I would just keep modifying the inputs to match my 500 actuals but they were still off at 1000 yds. Keep looking, you will figure it out.</p></blockquote><p></p>
[QUOTE="TexasHunter, post: 566361, member: 26082"] Wile, Don't know what your calcs were but here's what my calculator gave me. Berger 7mm / 168 / G7 BC = .316 / 3030 fps / sight height 2" DA=1000, 300yds=2.9moa, 400yds=5.0moa, 500yds=7.4moa, coriolis off DA=2000, 300yds=2.9moa, 400yds=5.0moa, 500yds=7.3moa, coriolis off DA=3000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.3moa, coriolis off DA=4000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.2moa, coriolis off DA=5000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.2moa, coriolis off DA=5000, 300yds=2.8moa, 400yds=4.9moa, 500yds=7.1moa, coriolis on @ 90º In general, Berger BCs seem to be the most accurate of the different makers. Using 3255 fps drops the 500 yd dope to 5.9 moa with coriolis on at 5000 DA. I stopped at 5000' DA but that doesn't mean you weren't shooting in a much higher DA. I shot a match in OK back in Sept where the actual altitude was 1200'. When we started at 8am the actual DA was 2100' and by the time we finished at 4pm, the DA was almost 5000'. We were shooting east on every stage and back at the range HQ after the match several guys were complaining about their dope being too high out at 1000 yds toward the end of the match. I asked if they input DA and they said "sure we did, this morning". When they re-measured and re-input while we stood there, they were ****ed that they hadn't considered the massive change as the day warmed up. There is also the possibility that different bore / groove configurations have varying effects on the actual BC but it would have to be huge to change the 500 yd dope by 1.2 moa so not a very likely culprit. Head and tail winds can also effect elevation to some degree but again not this much this close. Bottom line is that I personally fought this issue for years and until my wife gave me a Kestral 4500 last Christmas and I was able to measure and input DA directly, I never had confidence in my calculations. I would just keep modifying the inputs to match my 500 actuals but they were still off at 1000 yds. Keep looking, you will figure it out. [/QUOTE]
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