A local shop has 6-20 x 50 Redfield Illuminator for sale. with Target Knobs, (Japan model) I tried it on my steyr rifle and could not get it to zero due to limited reticle movement. I got what appeared to be a total of 6 in Elevation and 6 in Windage movement. Am I missing something on zeroing this scope.

there isn't alot of adjustment in this scope. You will probably find that using rings with some sort of built in adjustment will solve the problem.