I know this topic has been discussed at length but I'm not sure this was covered. How do you determine what is Spin drift and what is Coriolis? Here is an example to set a basis for the question. When setting up your ballistic software (mine is Exbal) you need to measure your spin drift at 5 or 6 hundred yards in calm conditions. OK no problem. If you use the Coriolis effect option in the software with a latitude of 45 and a target direction of 270 @ 600 yards I see that my bullet will impact .9" to the right and .9" low. Do I assume that Exbal's coriolis calculation is correct and subtract what it gives me from the spin data I collect? If I add spin on top of that I know it can't be right.