well...I went out to Pepboys and bought the gauges....anyway...they dont line up at all with my original mounting...(I hit 1000yards at Quantico with no windage and holdover at all once before..of course with no wind)
I usually use the EXD from Brownells that makes sure you are mounting according to the bore not a base...
Since it didnt line up, I took everything off and bubbled the base...ITs a Badger clipslotted steel Base on my GAP M40A3
Sure enough the bubble on the level moved from being centered to off to one side a little as you move back...Unless there is a milling issue, the base must have warped during install or torqueing....It was the same with my other ROCK rifle with standard Badger base...
Gauge idea is nice but not necessarily perfect if there are any imperfections with the scope base.