What is Parallax in Long Range Rifle Scopes?

Parallax is an optical phenomenon that occurs when the position or direction of an object appears to change when viewed from different positions, due to the angle at which it is seen. In the context of long-range rifle scopes, parallax refers to the apparent movement of the reticle in relation to the target when the shooter's eye position changes. This can lead to inaccurate shot placement, especially at longer distances, if not properly adjusted.

Understanding Parallax in Long Range Rifle Scopes

Parallax in long-range rifle scopes can affect shooting performance in various ways:

• Apparent Reticle Movement: When a shooter's eye is not perfectly aligned with the optical axis of the scope, the reticle may appear to shift in relation to the target. This perceived shift can cause the point of aim to deviate from the point of impact, leading to inaccurate shots.
• Parallax Error: The discrepancy between the point of aim and the point of impact due to parallax is called parallax error. As the range to the target increases, parallax error becomes more significant and can lead to larger shot groupings or missed targets.

Long-range rifle scopes, such as the Vortex Optics Viper PST Gen II 5-25x50 FFP or the Nightforce Optics 5-25x56 ATACR F1, often feature parallax adjustments to help shooters minimize parallax error.

Adjusting for Parallax in Long Range Rifle Scopes

Many long-range rifle scopes feature parallax adjustments to help shooters minimize parallax error:

• Adjustable Objective (AO) Scopes: Scopes with an adjustable objective, like the Leupold VX-3i LRP 6.5-20x50mm, allow shooters to correct for parallax by rotating the objective lens housing. This adjustment focuses the target image on the same focal plane as the reticle, reducing parallax error.
• Side Focus (SF) Scopes: Some scopes, such as the Vortex Optics Razor HD Gen II 4.5-27x56, feature a side focus knob, typically located on the left side of the turret housing. This knob adjusts the internal lens elements to compensate for parallax, bringing the target image into focus on the same plane as the reticle.
• Fixed Parallax Scopes: Scopes with fixed parallax, like the Schmidt & Bender PM II 5-25x56, are typically factory-set to be parallax-free at a specific distance, usually 100 or 150 yards. These scopes may still exhibit some parallax error at longer distances, but the error is generally minimal within the scope's intended range.

How to Adjust for Parallax in Long Range Rifle Scopes

To adjust for parallax in a long-range rifle scope, follow these steps:

1. Set up the rifle on a stable platform, aiming at the target.
2. While maintaining a consistent cheek weld, move your eye slightly behind the eyepiece to observe any reticle movement relative to the target.
3. Adjust the parallax adjustment (either AO or SF) until the reticle remains stationary in relation to the target while shifting your eye position. For example, if you're using the Vortex Optics Viper PST Gen II 5-25x50 FFP, turn the side focus knob to eliminate parallax error.
4. Re-confirm your point of aim and make any necessary elevation or windage adjustments.

By properly adjusting for parallax, shooters can minimize parallax error and achieve more accurate shot placement, particularly at longer ranges.

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