Rifle scopes & Shims

Shimming may be required to properly align the riflescope to the bore of the rifle. 

Major adjustments of the scope's elevation and windage are usually not needed. If major adjustments are needed, shims should be used for elevation. Shims are thin pieces of paper or plastic or aluminum (can) that are put under the scope's rings to either raise or lower the shot. Elevation adjustments should be reserved for minor correction. Over adjustment of the elevation (or windage) controls may damage the scope.

Determining shim thickness will take several tests. With one of my scopes I used both a small thin piece of paper and plastic. Positioning the shims can be a bit of a challenge. My rifle has a Picatinny rail, I cut the small pieces thin enough to fit in the rail's slot. The ring needs to fit snuggly over the shims.

If the rifle rings attach to a flat surface (non-picatinny) place a shim under the scope ring (either front or rear). An aluminum can be used for a shim. Cut a small piece and press it down so it matches the contour of the ring. Bend, mark and cut the excess metal so the shim is contoured to the scope ring base.

Place the shim under the scope ring you want to raise. To raise your shot (shooting low), put a shim under the back ring. To lower it (shooting high), put a shim under the front ring. Re-install the scope on the rings. Tighten the screws to the manufacturer's recommended torque setting.

It will take several repetitions using various shims (of various thicknesses) to sight in the scope.