Understanding Parallax

Understanding Parallax — How It Affects Accuracy & How to Correct It

Parallax is one of the most commonly misunderstood topics in rifle optics. A proper understanding of what it is, how it affects point-of-impact, and how to correct it is essential for long-range precision and consistent accuracy.

In simple terms: parallax occurs when the reticle appears to move against the target when your eye shifts behind the scope. If parallax is not corrected, this apparent movement can shift the point of impact — even when the rifle itself never moves.

What Is Parallax?

Parallax is an optical phenomenon that happens when the reticle and the target are not perfectly focused on the same optical plane. When this happens, small movements of your eye cause the reticle to appear to float or drift over the target.

This can lead to:

• Shifts in point-of-impact (POI)
• Inconsistent groups
• Wobble or “reticle drift” when moving your head
• Missed shots at longer distances

How Parallax Affects Accuracy

At close ranges (inside ~100 yards), parallax error is usually minimal. However, as distance increases, even small amounts of eye shift can cause noticeable POI deviation. This deviation becomes more pronounced at:

• Higher magnification
• Longer distances (300+ yards)
• Precision shots on small targets
• Unsupported or awkward shooting positions

If the reticle appears to move relative to the target when you move your eye, parallax is present. Even a slight drift can translate into several inches of POI shift at long range.

How to Check for Parallax

To verify whether parallax exists at your current magnification and distance:

1. Point the rifle at your intended target and hold it steady.
2. Without moving the rifle, slightly shift your eye left/right and up/down behind the ocular lens.
3. If the reticle appears to move over the target, you have parallax.
4. If the reticle stays locked in place on the target, parallax is correctly adjusted.

How to Correct Parallax

Most modern Burris riflescopes use a side-focus or adjustable objective (AO) system. The goal is to align the reticle and the target onto the same optical plane.

To correct parallax:

1. Turn the side-focus (or AO) knob toward the distance you are shooting.
2. Look through the scope and perform the eye-shift test again.
3. Fine-tune the knob until:
   • The target is crisp and sharp, and
   • The reticle no longer moves relative to the target

Important: The yardage numbers printed on the parallax dial are approximations. Always rely on the reticle-movement test for true parallax elimination.

Common Parallax Mistakes

• Using the parallax dial as a focus knob — target focus is a side effect, not the purpose.
• Leaving parallax “set at 100 yards” for all distances.
• Testing parallax inconsistently — always check with eye movement.
• Believing parallax only matters past 300 yards — it can matter at 50–100 yards on small targets.

Parallax Quick Reference

Distance	Parallax Risk	Recommendation
Inside 100 yd	Low–Moderate	Use minimal magnification, verify with eye-shift test
100–300 yd	Moderate	Adjust parallax for distance, test before each shot cluster
300+ yd	High	Fine-tune parallax precisely — even small shifts can cause misses

Final Tip

Anytime you change magnification or shooting distance, recheck your parallax. While a properly mounted scope minimizes error, only a quick eye-shift test guarantees the reticle and target are aligned on the same optical plane for true precision.