I just completed a scout rifle build on a mauser. I, too, used the XS scout mount. The method I used to install the mount is as follows: I first slid the XS scout mount on to the barrel and very lightly tightened the set screws on the bottom (just enough to provide some drag but still allow me to move the mount). Then, I placed the rifle in a gunvise, being sure to position the scout mount well clear of the vise so that I could adjust its position as needed. Using a wheeler engineering level-level-level, I first levelled the rifle, then levelled the scout mount to the rifle and tightened the set screws. I then carefully removed the rifle from the gunvise, turned the rifle over, placed it in the gunvise upside down, and removed one of the set screws. Using a spring loaded center punch, I marked the set screw location and reinstalled the set screw. I then repeated the procedure with the other set screw. Following this, I removed both set screws and the mount. Using a wheeler engineering v-block sight mounting tool, which incorporates a drill guide bushing, I centered each mark in the drill guide and lightly kissed each mark with a drill and a small drill bit. After that, I reinstalled the mount, verified that it was still levelled to the action, and acraglassed it to the barrel. I have since assembled and test fired the rifle, with outstanding results. Hope this helps.
