Leupold Double Dovetails eliminate the worry of loosening windage screws. They are bit tougher install, if you go this route use a 1" piece of dowel or pipe to twist in the dovetails not YOUR SCOPE! This is my favorite fixed mount, Iprefer 2 piece on bolts.

For detatchable or weaver style I like the Warne Maxima's as well.

Low rings should work withmost 40mm objective scopes.