Rifle Scope Mounting Guide

Safety first. Work only on an unloaded rifle with the action open and no ammunition at the bench. Torque values, ring and base fitting and anything mechanical are set by your rifle, base, ring and scope makers’ manuals; if anything doesn’t fit as the manual describes, take it to a gunsmith.

A scope that isn’t mounted solidly won’t hold zero. The Alaska Department of Fish and Game (ADF&G) makes checking the screws on the action, scope mounts and rings the first step of sighting in, because a loose screw ruins accuracy in the field. This guide explains bases and rings and gives a mounting checklist, following Wikipedia’s telescopic sight article, ADF&G, and your equipment’s manuals.

Bases and rings (Wikipedia)

• Two parts: a typical mounting system has a scope base on the receiver and scope rings that clamp the scope’s round tube. One-piece mounts with two built-in rings also exist, including cantilever designs.
• Ring size must match the tube: if the ring’s inner diameter doesn’t closely match the scope’s tube, the scope is either loose or stressed by being clamped too tight. The common sizes are 1 inch (25.4 mm), 30 mm (the most common today) and 34 mm.
• Rail types: common systems include 3/8-inch and 11 mm dovetail rails (often on rimfires and air guns), Weaver rails, and the Picatinny rail (MIL-STD-1913). Some makers use their own base systems. Rings must match the rail.
• Alignment: with rings screwed straight into the receiver, misaligned holes can bend-stress the scope tube; dovetail rails largely solved that, since a straight bar is easy to machine.

Mounting checklist

Follow your manuals for the order and values; this is the general sequence:

1. Clean and inspect the receiver, base screws and holes, and the rings.
2. Fit the base to the receiver with the screws the maker specifies, tightened to the maker’s torque. Use thread-locking compound only if the base or ring maker’s instructions call for it.
3. Fit the bottom ring halves to the base.
4. Set the scope in the rings with the top halves loosely in place.
5. Level the rifle in a rest, then level the reticle to it so the scope isn’t canted. Wikipedia notes the mount is meant to sit the scope without cant over the bore, which makes sighting in and holdovers easier.
6. Set eye relief: in your normal shooting position, slide the scope until you see the full image without a dark ring. Wikipedia notes typical eye relief runs from about 25 mm to over 100 mm, so check your scope’s figure against the rifle’s recoil.
7. Tighten the ring screws evenly to the scope or ring maker’s torque value, checking the reticle stays level.
8. Recheck everything before the range.

Bore sighting

ADF&G says bore sighting gets your first shots on paper at 25 or 50 yards. Most ranges have a bore-sighting device (collimator), or a gun shop or gunsmith can do it. On a bolt rifle you can bore-sight by eye: with the bolt out and the rifle on a solid rest, centre a 25-yard bullseye in the bore, then adjust the scope until the crosshairs sit on it.

First range visit

Sight in with three-shot groups at 25 yards, then 100 yards, letting the barrel cool between groups; our how to sight in your rifle guide follows ADF&G and West Virginia DNR step by step. Afterwards, our zero and holdover tool and shot placement tool help you use the zero in the field.

Sources

• Wikipedia, Telescopic sight (sections on mounting, rings and bases, eye relief). Read 28 October 2026.
• Alaska Department of Fish and Game, Sighting-in your rifle. Read 28 October 2026.

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Recommended Gear on Amazon

• Scope mounting kit with level - browse current options and reviews on Amazon.
• Inch-pound torque wrench - browse current options and reviews on Amazon.
• Laser bore sighter - browse current options and reviews on Amazon.

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