Dovetail sights are traditionally removed left to right and installed right to left, as viewed from normally shouldering the gun. What you need to do is raise some metal on the "floor" of the dovetail with a centerpunch. Make 3 equally spaced punch marks across the dovetail, angling slightly so the displaced metal moves from the dent to the right side of the dovetail. When you tap in the sight from right to left, it will "wipe" any excess metal back into the dent that way. A drop of red loctite under the sight will also help retain it. If using loctite, wait to install until you can sight it in as the Ruger is drift adjustable for windage and you want it dead on before the loctite sets up.