Calculating Proper Ring Height
To calculate the technical "proper" ring height, you first take the outside diameter of your scope's objective and divide it by two.
Nikon Monarch Gold 1.5-6x42 has an O.D. of 50mm. 50/2=25mm or .98 inches
This measurement is what the ring and bases combined will need to raise the scope at the centerline to above the receiver to clear a barrel that is the same diameter as the receiver.
Once you have determined this dimension, all you that is needed is to select a base and ring combination that equals that dimension plus 3 to 5mm to accommodate lens covers.
25mm+3mm=28mm or 1.10 inches
Now we need to figure out how thick our base is, or how far above the receiver the base protrudes. In this case our Remington 700 base is 7mm thick.
28mm-7mm=21mm or .82 inches
Now you know you need rings which are larger than this dimension, in our case .82 inches or 21mm.
Manufacturer's ring heights are not uniform from brand to brand.
This is a very often missed and important fact that most people do not know. Weaver's low ring's height is not the same as Leupold's or Burris' low ring's height. To properly calculate for your scope's height you must go by the ring's actual measurements.
The actual measurement of "ring height" can be determined in two different ways depending on the manufacturer. Some manufacturers measure from the top of the base where the ring contacts the base to the centerline of the ring (A in the illustration). Other manufacturers measure from the top of the base to the bottom of the saddle where the ring first contacts the scope (B in the illustration). If the particular brand you are considering measures ring height like as B, you will need to add 12.7mm for a one inch scope and 15mm for a 30mm scope to get to the centerline of the ring which is also the center line of the scope.