Back in the mid 70's, I ran a large gun shop in Boise, Id, and sold a lot of Ruger M77's. We always mounted scopes on them for the customers, and I found many M77 cast in bases off enough that you had to screw the wind-age all the way on a scope, and sometimes that was not enough. When you have mounted scopes on about 300+ M77 in a 10 year span, you will find a lot of the bases off. Luckily we had a very good gunsmith with us that could shim the ring, or actually mill out part of the ring. I understand that today most scopes have more wind-age adjustment built into them, which makes it easier to mount scopes on M77 rifles. My last new M77 I bought was a stainless 223, about 1992, and the scope I installed had plenty of wind-age and elevation.