How to mount a scope on an AR-15

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How to Mount an AR-15 Scope

If you’d like a brief introduction or refresher course on how to mount a rifle scope on an AR-15, you’ve come to the right place. The experts at Warne Scope Mounts have been designing American-made rifle scopes and other firearm accessories for decades. This means we know a thing or two about how to properly mount an MSR scope – and prevent performance-hindering scope slippage or misalignment.

Scope Mounting Tools

Regardless of if you’re working with one-piece or ring mounts, you’ll need a few tools to fit your scope to your AR-15. If you don’t have them already, these are the tools you need to get:

  • A torque wrench for attaching your mount to your rifle.
  • A hex key (that came with your scope and mount) or precision screwdriver bits for attaching the base and rings.
  • Small bubble level(s) to align the scope, ensuring its accuracy.
  • A gun rest or workstation with plenty of space for using bubble levels to double-check your scope’s precision placement on your rifle.
  • Rubbing alcohol for cleaning different scope components (rail, rings, screws, etc.) while installing your mount and scope.
  • An AR-15 scope (obviously) with scope rings and any other pieces needed to mount your scope. There’s a good chance your scope will come with most – if not all the tools – you’ll need to mount it.

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Mounting a Rifle Scope on an AR-15

Once you’ve purchased your correctly-sized one-piece (cantilever or non-cantilevered) or ring mounts, gather your tools at your workstation/shooting rest. Here are the basic steps you’ll need to follow to mount your scope to your AR-15:

1. Rifle Safety ­- Ensure your AR-15 is empty. Removed the magazine. Make sure the chamber is empty. Double-check everything.

2. Shooting Rest – Secure your rifle firmly onto your shooting rest or gun vise. The last thing you want is for it to wiggle around while you’re working on it. Check levels with your bubble level.

3. Cleaning – Use rubbing alcohol and gun cleaning patches to wipe oil and grease off the mount, rail, screws and other mounting components.

4. Placing the Mount – Carefully set the mount atop the upper receiver. Try not to place it on the free-floating rail. You want to avoid adding excess stress to the rifle’s tube.

5. Tighten the Scope Mount – First, hand-tighten the scope mount. Once it’s hand-tightened, use the torque wrench to fishing screwing it down according to the factory specifications that came with your mount.

6. Adding the Scope ­- Verify that your rifle is level in a gun vice or at your workstation. Place the optic of your MSR rifle on the mount, with the rings resting on the flat surface of the scope.

Secure the top section of the scope rings over the scope, tightening them with an “X” pattern – but don’t lock them down completely. Make sure there’s a small gap on each side of the ring for positioning the optic. Now you can adjust the proper scope eye-relief. Once you’re happy with the distance between your eye and the scope, put the top caps on. Then tighten the screws down to keep the scope from sliding in the mount.

7. Leveling ­- Check once again that your AR-15 is level in your gun rest. Then verify the reticle alignment and adjust if necessary.

Now set your bubble level on a flat scope surface and check parallel and perpendicular levels. After everything is level, use the “X” tightening pattern to tighten the rings down. One last time, check the levels and reticle alignment. If everything is still level and accurate, give yourself a big pat on the back – because you have successfully mounted a scope on an AR-15 rifle.

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