Level that Scope Reticle
MOST RIFLE AND accessory manufacturers now use precise CNC machining, so correct scope mounting is no longer difficult. Many shooters go through the procedure of mounting, bore-sighting and zeroing, only to find the reticle has a slight cant. If forced to do this at the range or in the field, you may not have the right equipment on hand. A small spirit-level is required; you should keep one in your shooting box.
A tilting reticle is distracting and adversely affects practical accuracy. Precisely accurate holdover and windage allowance is possible only if the respective crosshairs are perfectly vertical and level. The scope turrets’ tracking system works vertically and horizontally, not at angles. Canting becomes more problematic at longer ranges, with shots hitting left or right of point of aim, depending which way the rifle tilts. This can be rectified with minimal equipment.
One way to ensure the reticle’s fidelity is to hang a plumb-line from a target frame or other solid structure on a windless day, for reference to the vertical crosshair. Adjust the scope-rings’ screws to enable the tube to rotate smoothly (but not loosely) within the rings. Cradle the rifle in an X-bag or pack it tightly between sandbags so that the scope’s vertical crosshair more-or-less coincides with the plumb-line. Some shooters position the crosshair next to the plumbline; others on it.
Place a small spirit-level on any flat, level surface of the rifle’s receiver to ensure the rifle is resting perpendicularly. Then rotate the scope until the vertical crosshair covers the plumb-line or is precisely parallel with it. Now tighten the ring screws progressively in even stages, starting with the righthand rear screw, then the left front one, followed by the right front, and finally the left rear. Repeat this figure-8 pattern until all are fully tightened. This will perfectly align the reticle with the rifle’s perpendicular axis, without requiring a second pair of hands.
If you’re worried that the scope might move during the screw-tightening process, make use of a thin but inflexible square object such as a flat iron bar (you’ll need a friend to assist you). Insert the bar between the flat underside of the turret base and the top of the receiver. If the rifle has an integral Weaver-style or Picatinny rail, this helps. Your friend twists the bar so that it applies light pressure to both surfaces, and maintains this pressure while you tighten the scope-ring screws as described above. Obviously, the bar must be held perfectly still or it might shift the scope.
A SIMILAR PROCEDURE can be carried out in a dark room. With scopering screws loosened as described above, secure the rifle as before, aimed at a wall. Using a spirit-level, adhere a length of masking tape horizontally on the wall at scope height, and draw a precisely horizontal line on the tape. Now shine a torch-beam through the ocular lens and align the shadow of the lateral crosshair with the drawn line. Use a spirit-level to level the rifle. Rotate the scope until the crosshair’s shadow precisely coincides with the drawn line or is closely parallel. I find parallel best, as it keeps both shadow and line visible. Now tighten the ring screws while checking the shadow-to-line reference remains unchanged.