Mounting a Scope
When you’re mounting a scope on your air rifle, the first thing you need to do is to determine where your eye relief is. To do that, you mount the rings loosely on the gun – firm enough to stay on but not so loose as to fall off. Put the scope on, set it on the highest power (because that’s where eye relief is most critical), and gently position it for your eye relief when you are in correct shooting position.
Here’s how to make sure you have the eye relief set correctly: mount the gun with your eyes closed. Relax your head and neck, then open our eyes. If you move your head forward, the scope needs to come back. If you move your head back, the scope needs to go forward. And, if you don’t move your head at all, the scope is positioned properly. If you’re not sure if you’re moving, ask a friend to observe you.
Once you get the eye relief properly set, tighten down the bolts that hold the scope rings to the scope rail on the rifle. At that point, it’s time to get the crosshairs aligned straight up and down.
Don’t try to do this by pulling the gun to your shoulder. That’s because tight handed shooters will tend to cant the rifle to the left, and lefthanders will tend to cant to the right. Instead, set the gun in a solid rest, make sure the gun is level, and sight on a plumb bob or the corner of a wall to get the crosshairs vertical.
When the crosshairs are squared away, it’s time to tighten the scope in the rings. Tighten all the top strap screws until they are just barely snug, with an even gap on the left and the right side of the scope. Then tighten each screw in an X pattern, one-eighth of a turn at a time. Do four cycles of tightening on the front mount, then four cycles on the rear mount, then repeat as needed. Make sure you are maintaining an even gap from side to side as you complete your tightening cycles. You want to get them as tight as you can on a spring gun.
If you find you don’t have enough vertical adjustment to get the scope sighted in, you can place a shim under the scope on the rear mount to compensate. You can use brass sheeting from a hardware store or plastic cut out of standard water bottles. Better yet, ask your airgun dealer for a scope mount that is adjustable for elevation.
Finally, whether you have an airgun with iron sights or a scope, you’ll want to sight it in. Sighting in is simply the process of making sure that, at a given distance (ten yards, for instance), the sights are pointed at the same spot where pellet or BB hits.
The easiest way is to start at a distance of 10 feet (That’s right, 10 feet, not 10 yards. A tip of the hat to Tom Gaylord, former Editor of the Airgun Letter for this suggestion.) Shoot one shot with the sights centered on the bull’s-eye.
Look at where the shot hit. Ideally, the point of impact should be no more than 3 inches below the bull’s-eye and centered from side to side. If the shot is too high or too low, or to the right or to the left, consult your airgun or scope manual and adjust the sights accordingly.
Take another shot from ten feet and see if your adjustments are getting you closer to where you want to be. Make small changes at first until you get a sense for how changes in the sight settings affect the point of impact. The windage adjustment changes where pellets strike from side to side, and the elevation knob or screw adjusts the height. Continue making shots and changes until your pellets or BBs are striking the target 1-3 inches below the bull’s-eye and centered side to side.
Next, move back to ten yards, and shoot again. Your shot should hit the target a little higher and should remain generally centered left to right. All that remains is to fine-tune the windage and to adjust the elevation so your shots hit the center of the bull’s-eye. That’s it – your air pistol or rifle is now sighted-in for ten yards. If you shoot from a distance other than 10 yards, you’ll notice that your pellets or BBs will strike higher or lower, depending upon the range.
A couple of notes: if you back up to 10 yards, and find your shots are going wild, return to 10 feet, check to make sure the fasteners holding your scope or sights haven’t worked loose, and try again. If you are shooting a multi-stroke pneumatic air rifle or pistol, be sure to use the same number of pumping strokes each time.
Til next time, aim true and shoot straight.
– Jock Elliott