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Old August 9, 2005, 01:11 PM   #9
Oldphart
Senior Member
 
Join Date: May 19, 2004
Posts: 375
When I began long-range shooting, I dutifully recorded the published BCs of the bullets I was using. Then I went to the range and found they were different.
I use a 155 grain bullet that is supposed to have a BC of .450. That's close enough to get me on the target but far enough off to make me fiddle with the numbers. According to my notes, my come-up for 300 yards is 4 MOA, for 600 it's 14 MOA, for 800 it's 22.5 MOA, for 900 it's 27.5 MOA and for 1000 it's 36 MOA. I plug different BCs into Pejsa's program until I can come close to all those values and find the real BC is closer to .393.
I have spoken to a few representatives of bullet manufacturing companies and have asked them how the derive their BCs. Invariably, they tell me the data comes from their "Ballistics Lab." as if such a lofty pronouncement will stifle any other questions. I have yet to see data from Sierra, Nosler or any other company that indicates they actually measure the trajectory of their bullets. In the absence of any such data I have to assume their values are established as much by their marketing analysts as their ballisticians.
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