What Does AO Mean on a Rifle Scope?

When shopping for or using a rifle scope, you may come across the abbreviation AO — but what exactly does it mean? AO stands for Adjustable Objective, a feature found on many rifle scopes that allows shooters to fine-tune their optics for better clarity and accuracy.

Let’s explore what AO does, how it works, and whether you need it on your next rifle scope.

What Is an Adjustable Objective (AO)?

An Adjustable Objective (AO) is a mechanism on a scope that allows you to manually adjust the focus of the reticle to match the distance of your target, eliminating a common optical issue called parallax.

Unlike standard scopes with a fixed parallax setting (often fixed at 100 yards), AO scopes have a rotating ring (usually located on the objective bell at the front of the scope) that you can turn to correct for different target distances.

What Is Parallax — and Why Does AO Matter?

Parallax occurs when the reticle (crosshairs) appears to shift position against the target when you move your eye behind the scope. This can cause accuracy issues, especially at longer ranges or when aiming at small targets.

AO scopes allow you to eliminate parallax by aligning the reticle and the target on the same focal plane — meaning, even if your eye position shifts slightly, the point of aim remains true.

How Does an AO Scope Work?

  1. Turn the AO dial to match the distance to your target (usually marked in yards or meters).

  2. Look through the scope and check for clarity and crosshair stability.

  3. Fine-tune if needed until the image is sharp and the reticle doesn’t move with slight head movement.

When Should You Use an AO Scope?

AO scopes are especially useful in the following scenarios:

  • Precision shooting or target shooting

  • Small game or varmint hunting

  • Shooting at varying or long distances

  • Using high magnification (10x or above)

For example, if you're trying to hit a squirrel at 60 yards or sighting in at 200 yards, AO helps ensure your scope remains crystal clear and accurate.

AO vs. Side Focus: What’s the Difference?

Some modern scopes feature side parallax adjustment (also called side focus) instead of a front-mounted AO ring. Functionally, they achieve the same result — parallax correction — but the side focus knob is easier to adjust without breaking your shooting position.

AO is typically found on hunting and budget-friendly scopes, while side focus is common in tactical or high-end scopes.

Do You Need an AO Scope?

You might not need AO if:

  • You only shoot at fixed ranges (e.g., always at 100 yards)

  • You use low magnification (under 9x)

  • You're shooting large targets where minor parallax isn’t an issue

But you should consider AO if:

  • You shoot at varying distances

  • You demand high precision

  • You use high-powered magnification

  • You shoot rimfire rifles or airguns, which often experience parallax at short ranges

Final Thoughts

AO, or Adjustable Objective, is a valuable feature that gives shooters more control and precision, especially when dealing with variable distances and high magnification. By correcting parallax and improving image clarity, AO scopes help ensure that where you aim is where your shot lands.

If you value accuracy and shoot at different ranges, an AO scope can be a game-changer in your shooting performance.