Sometimes other factors may determine an incorrect value. If you have a chronograph and have correct velocities, then you may be off on the BC #s. While doing drop data on my 308 last fall, I did not have my chronograph so I assumed my velocities were on. My value was 1.5 moa off(600 yards). I assumed my BCs were off on that bullet until i ran thru the chronograph. My velocities were much higher than thought. Once I put those velocities in my ballistic program, the BCs went back to there published numbers. Either way, my drop data was on but just properly so in the end.With any program you need to know your muzzle velocity.
I use Ballistic AE.
Once I get my come up - I change the BC till it matches my dail reading(s).
I
BAE gets current weather conditions in the HUD window.