Re: ballistic calculator accuracy
its only as accurate as the data its fed.
most probably your actual BC is different from the published one.
Here is what I do, don't know if its right or not but it works well for me.
sight in at 300 yards, on a large target
shoot (with a 300 yard zero) at the same target at 400, 500, 600 yards
measure your actual drops
tweak your BC in the ballistic program until your chart matches your actual trajectory.
In my 7mm AM I must use a BC of .62 to hit where I aim with a 160 accubond, nosler says its .531
I use a .7 BC for a 140 berger, berger says its .64.
Now I'll tell ya my experience with JBM
was working with my 6.5 gibbs, had all my load testing done but my PDA hit the skids, so the night before deer season I went to the sight and printed me out a range card, using my tested data. the next morning I took a whitetail at 787 yards using that range card. its a mathematical formula, feed it the right info and it'll be right.
Born to Hunt, Forced to Work!