I have a pre 1975 Herters 300 win. mag. It was manufactured in England. My son got me a Redhead (bass pro shop house brand) 3.5 x 9 scope. The original scope is a fixed power Herter's, 6 power. The new scope won't work because the front will hit the barrel using the old mounts. I've taken the gun to a couple shops and my dovetailed rail is slightly smaller than any standard gun. So Weaver, Leuopold, and a couple other brands won't fit. What should I do? I need to raise up about an 1/4"