The Parallax Bugaboo

Q: I have been shopping around for a new scope for my Browning X-Bolt .270 and have been offered several models that have parallax adjustment. At high school I must have slept through the lesson on optics. Can you bring me up to date on the subject? How do you recognize Parallax if it is present in a scope?

Patricia Howell

A: Parallax can be detected by getting the scope on a steady rest, placing its crosswires on the centre of a target at say
100 yards, and while looking through the scope, moving your head from side to side. If parallax exists, the reticle will appear to move from side to side on the target. This presents no real problem as long as the eye is perfectly aligned with the centre of the scope, but if the eye is not perfectly centred for each shot, points of impacts of bullets fired into a group will be

This example shows correct parallax at the top.

displaced by the amount of parallax (or eye misalignment).The eyepiece (ocular lens) is adjusted to focus the scope for the individual shooter’s vision,, but parallax is adjusted to focus the scope at various ranges, either by having an adjustable objective or a third turret. Being able to completely eliminate parallax in a scope is extremely important if the scope is to be used for benchrest competition or other types of long-range target shooting, or on a high-magnification varmint scope. Hunting scopes with fixed objectives are usually adjusted at the factory to be free of parallax at 100 or 150 yards, and don’t need to be adjusted for parallax.

To see it graphically see the video below.

Nick Harvey

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The late Nick Harvey (1931-2024) was one of the world's most experienced and knowledgeable gun writers, a true legend of the business. He wrote about firearms and hunting for about 70 years, published many books and uncounted articles, and travelled the world to hunt and shoot. His reloading manuals are highly sought after, and his knowledge of the subject was unmatched. He was Sporting Shooter's Technical Editor for almost 50 years. His work lives on here as part of his legacy to us all.