I have my iron sights worked out on my .416 rem mag. Now I want to put on a scope in Leopold quick detach bases. Low height, medium height, high height. How do I figure how high to put the scope?

Leupold has a guide on their website (at least for their scopes, but you can estimate given the objective diameter):

http://www.leupold.com/hunting...ng/mounting-systems/

Look at the right-hand side of the page. You may have to scroll down a bit.

by how YOU want it setup, once the bell clears the barrel - no joke

You want to get a clear center full scope picture when you throw the rifle up to the shoulder.

Slow scope use in normally the result of improper mounting of the scope and the lack of practice.

And in most cases going from irons to optics will require a cheek riser. Your line of sight will be different unless you are mounting a fixed power straight tube scope and mount it low.

You will quickly adjust your cheek weld for the scope; but mount it as low as you can.