Over the years I have had many conversations here about what is the proper way to use MIL or MOA reticles for sight-in, hold-over, calling shots, etc. Today almost all scope manufacturers have seen the advantage of using the same unit of measurement in their reticles and turrets, ie, MIL/MIL or MOA/MOA. There are many advantages to this built right in to the scope that are seldom used.
So many guys are taught about the math side of MOA or MIL and force fed formulas and numbers. Focusing on the numbers is focusing on the linear measurement when we should be thinking in terms of angular measurements. MIL and MOA are both angular measurements and if you can force yourself to keep the math out of it for a while you will soon see the huge benefits of ignoring the math and embracing the technology built into every MOA/MOA or MIL/MIL scope. Especially in today's world of LRF's and ballistic apps there is very little need to get all caught up in the math.
I was in the process of creating some pictures to explain this when I came across this great thread on optics-talk. It does a great job of explaining the concept.
I hope it is helpful.
Sighting in a Mil/Mil Scope - The Optics Talk Forums - Page 1