There should be a "calibration" mark on the power ring or a note in the literature for the scope. When both scopes are set to the "cal" mark they should both indicate the same value(s).
Is the reticle in the first or second focal plane. My new 6.5-20 leuy tactical has the reticle in the first focal plane. My 2nd gen mil-dot reticle is accurate all power levels. If your reticle is in the second focal plane, then you'll need to use the calibration setting on the zoom ring.
If I hold a 4.5-14 mil-dot and a 6.5-20 mil-dot on the same target at the same yardage will the dots be in the same place on the target or are the dots in the 6.5-20 only half the distance. Thanks