Photo by Justin Appenzeller
All you need to correctly mount a scope so that the reticle is dead level, the eye relief is correct, and everything is tightened properly are a workbench with a vise, a small bubble level, and a torque wrench.
Clamp the barrel of the rifle in the vise, but first pad the jaws of the vise to prevent marring the metal. Use the bubble level, positioned perpendicular to the axis of the bore, to get the rifle centered. Usually scope bases are flat, making them an ideal spot to position the level.
Mount the scope and snug the rings so the scope remains in place but can be moved with some effort. Place the level on the flat of the elevation turret, again at 90 degrees in relation to the barrel, and center the bubble to get the reticle straight up and down.
Remove the rifle from the vise to check your eye relief. If it needs adjustment, put the rifle back in the vise, centering it. Move the scope either forward or back, re-level the reticle as needed, and test it again.
Once the eye relief is right, tighten the fasteners in the rings to about 23 inch-pounds and you’re good to go.