Here s my question for the experts - should one not be checking zero at 100 yds (assuming that is the zero and not say 300yds because of MOA range) before every time one tries a long range shot longer than 1000 yds when weather or altitude has changed. Obviously one checks zero after travelling but if for example, temperatures have gone from 70 to 45 or humidity has changed, should be zero not be checked before going for the long shot. This would also be to avoid ranging shots at the long range targets. Clearly, using exbal or whatever ballistics program of choice, this takes into account changes and one enters the new parameters but one assumes the zero is the same. Appreciate comments.