scope mounts for ruger m77 rifle are different hights. taller at rear, shorter at front. There are four heights available for 1in scopes. low, med, high and xtra high. They can be used to produce three different mounting heights for the scope, in combinations of low/med, med high and high and xtra high...Ok so far ?..It therefore seems strange that the ruger details for the height in ins for each mount is:- xh=.680 h=.565 m=.435 l=.325 which clearly means that the difference in height on the rifle itself needs to be .11 for low and med, .13 for med and high and lastly .115 for high and x high. so only one combination can be correct. Or am i missing something obvious ? Plenty of you out there must be familiar with the Ruger system, PLEASE tell me i'm wrong. Jim. uk.