How to Mount a Rifle Scope: An Owner's Basics Guide

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Before you start: tools and a safe bench

Clear the rifle, confirm it is unloaded by looking and feeling in the chamber and magazine well, and move ammunition to another room. Then gather:

• A torque driver or torque wrench that reads in inch-pounds, with bits that fit your screws exactly. Ill-fitting bits strip heads.
• A rifle rest or vise that holds the rifle steady and level without clamping on the scope.
• A small bubble level or a pair of levels, or a reticle leveling tool.
• Degreaser and a clean rag for screws and threads, plus whatever thread treatment the base maker specifies.
• The manuals for the rifle, base, rings and scope. They list torque values, screw order and any warnings.

Step 1: bases and rails

Your rifle determines the mounting interface. Most bolt-action rifles are drilled and tapped for bases; many come with a rail or a factory base. AR-pattern rifles have a Picatinny rail on the upper receiver. Some lever and rimfire rifles use dovetail grooves cut into the receiver.

Install the base with clean, dry screws unless the maker says otherwise, apply any thread treatment they specify, and tighten to their stated torque. Do not guess. A base that shifts will move your zero no matter how good the scope is.

Step 2: choose rings that fit

Tube diameter

Rings must match the scope's main tube: commonly 1 inch, 30 mm or 34 mm. The scope's specification sheet lists it, and a ring sized for one tube will not safely hold another.

Ring height

Rings come in low, medium, high and extra-high heights, and makers measure height differently. The goal is the lowest height that lets the objective bell clear the barrel (and any rear sight) without touching, while still giving you a comfortable cheek weld. AR-15s usually need taller mounts because the stock sits in line with the bore.

Two rings or a one-piece mount

A one-piece cantilever mount is common on AR-15s because it pushes the scope forward to set eye relief. Two separate rings are typical on bolt guns. Either works if it fits your rifle, scope and position.

Step 3: set the scope in the rings loosely

Install the ring bottoms, lay the scope in, and fit the ring tops with screws just snug enough that the scope can slide and rotate with light pressure. Keep the turrets clear of the rings and do not clamp on the turret housing or the bell.

Step 4: set eye relief for how you actually shoot

Eye relief is the distance from the eyepiece to your eye at which you see a full, clear picture. Too close and recoil can drive the scope into your brow; too far and you see a dark ring or a shrinking image.

1. Turn the magnification to its highest setting, where eye relief is most critical on most variables.
2. Get into the position you shoot most: prone, seated at a bench, or standing. Close your eyes, settle onto the stock naturally, then open them.
3. Slide the scope forward or back until the full image appears without shadow when your head is in its natural place.
4. Check at lowest magnification too. Leave a little room for heavy winter clothing on a hunting rifle.

If you hunt in cold weather, check eye relief again wearing your hunting coat. Our cold-weather visibility guide covers the related problem of fogging glasses.

Step 5: level the reticle

A canted reticle makes shots drift sideways as distance increases, especially when you dial or hold for elevation. The basic owner method:

1. Level the rifle in the rest using a flat surface on the action, rail or base as the reference.
2. Rotate the scope until the vertical crosshair is plumb. A level on the top of the elevation turret cap, a reticle leveling tool, or a plumb line hung at a distance all work.
3. Recheck the rifle's level, then the reticle's. Repeat until both agree.

Some shooters also add an anti-cant bubble level to the scope tube or rail for field use.

Step 6: tighten to specification, in sequence

This is where most damage happens. Ring and scope makers publish torque values in inch-pounds and a tightening pattern, typically alternating screws a little at a time so the gap between ring top and bottom stays even. Follow those numbers exactly. Too little torque and the scope slips under recoil; too much and you can dent the tube, bind the internals or strip screws. Never exceed the lowest of the ring maker's and scope maker's limits.

Recheck level after tightening, since the scope can rotate slightly as screws come down.

Step 7: bore sight, then zero

Bore sighting gets you on paper; it does not replace zeroing. On many bolt guns you can remove the bolt and look through the bore at a distant target, then adjust the reticle to match. Laser bore sighters are an alternative. Then go to the range and zero with the ammunition you will actually use, shooting small groups from a solid rest and letting the barrel cool between them. Our fall range checklist lists what to bring.

Common mounting mistakes

• Mounting the scope without setting eye relief in a real shooting position.
• Skipping a torque driver and "feeling" it.
• Using rings that are too tall, which lifts your head off the stock.
• Clamping a ring on the turret housing or the objective bell.
• Forgetting to check base screws, which can loosen independently of the rings.
• Never rechecking. Inspect screws after the first range session and before each season.

Optics and mounts

For a close look at a hunting rifle that takes a classic two-ring setup, see our Bergara B-14 Timber review; for AR setups, see hunting with an AR-15.