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Discussion Starter · #1 ·
One of my friends is shooting a Barnes 180gr TSX from his 300WM. He found a load that groups well, so we chrono'd the load, ran ballistic calculations, and then sighted in. Then we started shooting at distance to verify that trajectory matches the calculations. His trajectory matches our calculations pretty well out to 400 yards, but at 500 yards the bullet drop is suddenly 15 inches more than calculated. It is as if the BC is changing RADICALLY somewhere between 350 and 500 yards.

I have stayed away from Barnes bullets, so I have no experience with them. Anyone have any thoughts as to why this might happen? I have an theory, but I am not sure I believe it, and I am not wanting to post it just yet. If you have some ideas on this, please let me know.
 

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Your BC changes as your speed changes. This may cause the rapid change.

This if for a .308gr 175 SMK
.768 @ 2300 fps and above
.760 between 2300 and 1800 fps
.750 @ 1800 fps and below
 

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Discussion Starter · #3 ·
True, but the small BC changes you are noting shouldn't be enough to account for the huge error in trajectory as near as I can tell. It takes a much, much greater change in BC to match the trajectory at 500 yards, even if carried over the entire time of flight. When adjusting the BC by enough to account for the 500 yard drop, then the trajectory at 300 and 400 is way off.
 
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