Ok, this is really easy, but difficult to put into words.
slowly move your scope to a centered position, move it up down and count the clicks between all up and all down. Move to 1/2 of that distance/clicks. then it is elevation centered.
Then do a centering on the windage; all right --all left and count those clicks; then put it at 1/2 that number of clicks.
The internal adjustments on your scope are now centered.
Take it to the range and shoot at a large 3'x3' target at say 50 yards. shoot 5 shots and see how high or low the group is. For this say the group is 15 inches high at 50 yards.
Now it is a simple ratio of the distance and the amount high (or low) all in inches. in the example the 50 yards is 1800 inches so the ratio on a high group is 15"/1800" or .00835.
We apply that ratio to the distance between the front and the rear scope bases, assume that distance is 6 inches.
6" time 15/1800= .05inches If the group is high you will need to raise the front mount UP .05 inches. If the group is low then you need raise the REAR mount that ammount.
Just buy some shims (Burris #625051) and place a .05 thick shim under the front mount (between the bottom of the mount and the receiver ring, tighten base screws and you are there.
Burris Scope Base Shims http://www.midwayusa.com/viewProduct...tNumber=585609