Something is awry when two ballistic codes don't closely agree.
Maybe its because you guys are upside down down there and the bullets are falling up instead of down.
One to try is JBM ballistics. Google will find it quickly.
What you may try is to shoot at a very large target at several distances out to your max distance. This will tell you what your drops are. The two variables you won't be sure of are MV and BC. But you will know your drops and hitting stuff is what's important.
0.33 is a quite puny bc for a 243 projectile. I haven't looked it up but would be much more comfortable with a 0.6 or a little better.
Just a thought....