When I run JBM and Jacksonrifles.com against each other I get 1.2 MOA difference at 600 yards. I thought I would see differences, but that seems extreme. I was careful to enter the exact data in both, including elevation, wind, pressure, etc.
What gives? Since it SHOULD all be science by now, I would think that any error would be rounding and minimal.
Which JBM chart are you using? I have found the small drop charts are off and need tweaking but the main trajectory cal is good and will match with other quality ballistic calculators.
If you post up your data we could have a look at it. I'm running Loadbase 3.0 and out to about 1000yrds JBM is fairly close if I have everything spot on, maybe give you some more perspective.
"Pain is weakness leaving your body"