Mounting a scope properly lays a foundation for straight shooting. A scope that isn’t solidly affixed to your rifle can shift around, moving your bullet’s point of impact. Fortunately, scope mounting isn’t difficult to do yourself.
We’re assuming, before you begin, that your rifle is drilled and tapped for a base or bases and you’ve bought the correct base(s) and rings for your model of rifle. Rings come in three heights — low, medium, and high — to fit scopes with varying sizes of objective lens. As a rule, the lower you can mount the scope over the bore, the better. Be sure you can work the rifle bolt freely at whatever height you choose.
It’s easiest to mount a scope on a rifle that is held securely in a padded gun vise. If necessary, you can improvise a holder by cutting notches in either end of a stout cardboard box.
1. Clean any grease off the screws, screw holes, and bases with Outers Crud Cutter or lighter fluid. Wipe the metal dry; then lightly oil the top of the receiver where the base will sit. Set the base on the receiver. Put a drop of medium-strength Loc-Tite on each screw (don’t use the strongest stuff, which can only be undone with heat). With a screwdriver that is the same blade width and thickness as the screw slots, turn the base screws down as tight as you can.
2. Install the bottom halves of your rings per the manufacturer’s instructions. With Redfield, Leupold, and some other brands, the front ring attaches to the base through a socket arrangement that requires twisting the ring 90 degrees. Never use your scope as a lever to twist the ring; you can easily bend the tube. Instead, use a length of 1-inch wooden dowel or pipe.
3. Lay the scope onto the bottom halves of the rings. Attach the top halves of the rings, but don’t tighten the screws yet; you’ll want the scope to slide back and forth and rotate so you can adjust the eye relief and the cant. Don’t make the mistake of setting the scope too close to your eye, or it will hit you when it comes back under recoil. Most scopes have 3 to 4 inches of eye relief; that is, they are designed to be set 3 to 4 inches in front of your eye when you are leaning into the rifle with your head forward on the stock. Position the scope accordingly.
4. Now, adjust the cant to make sure the scope’s crosshairs are truly vertical. With the gun in a vise, use a small level to check that the rifle itself is not leaning to one side. Then, sight through the scope at a straight line you’ve checked with the level, such as a door jamb or window frame. Turn the scope to line the crosshairs up with the vertical line.
5. Tighten the ring screws. They should be snug enough to hold the scope securely, but they needn’t be cranked down as tightly as the screws that hold the base to the receiver. With split rings that have screws on both sides, tighten the screws alternately, so the gaps between the rings come out even.