2 MOA impact change at 700 yards?
I have a 6.5/280 Ackley Imp that I have been shooting at 700 yards. I shot at the same target two days in a row with different results. One day I dialed 13.5 Min of elevation, and the next I had to dial 15.5 to hit center. The conditions were very simular on both days. The temp perhaps fell from 70 to 50, and the humidity could have risen from 70 to 90%. I have tried the JBM program to try to explain the difference in impact but have had no luck. There was almost no mirage as it was mostly cloudy on both days. I am stumped at this point. I am hoping someone can shed some light on the reason this can happen, other than a bad scope or mounts. It has a Leupold VX III 6.5-20x40 with 30mm tube, in Leupold mounts, which are tight. It's a Model 700 that shoots in the .5's. I'm just getting going at over 600 and have not had this problem so far, and I've shot a lot at 600.
Does my scope have a tracking problem?
Is there a mirage that I didn't notice that is making the target look higher on one day and not the other?
What else can make this happen?
Thanks for your time.