Just remember that every barrel treats a bullet differently, and therefore the BC for the same bullet will vary from barrel to barrel, sometimes such a small amount you wont notice it, othertimes a particular barrel will significant affect "how the bullet goes to sleep" and can have a significant affect on the bullets actual BC for some or all of the bullets flight.
You must confirm your actual BC either by shooting in known conditions (air density - pressure, temperature, humidity, this last is the least important) out to the longest range you're planning on shooting to, or by shooting across Oehlers acoustic targets out to your max range, or doppler radar. Not all of us have these last 2, so comparing shot drops and tweaking the program's BC to match works fine. Just be aware you need to calibrate your scopes actual adjustments (few are exactly what they say they are) and also you really need to do it in dead still conditions to make sure you aren't confusing any vertical wind effect as more or less drop and therefore a different BC.
If you don't calibrate your scope your drop chart will still work fine for your gun and load, its just your BC may not be what you think it is.
Hope this makes sense, this is a huge topic that really needs more discussion.