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Old 11-16-2007, 11:25 PM
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A little expansion on eye relief - copied from a post I made a while back on this. You can check Leupold's web site or catalog and it shows the optimal eye relief at both ends of the zoom range, something more vendors should do. Nobody really specs the eyebox, as it's a good bit more subjective and harder to measure with accuracy. Also, having your eye at different ends of the eyebox can affect things like how blurry the front sight of an AR is at lower mags.

ar15barrels' point about the distance is dead on - you can't really test a scope well at short distances, unless it's got AO that can focus down to household distances like 20-30 feet.

Quote:
There are 2 aspects to eye relief - the optimal spot for eye relief at a given magnification (this is what's usually spec'd by the vendor), and the window where you can get useful eye relief, often referred to as the "eyebox" (and rarely spec'd). The vendor's spec for optimal eye relief is often calculated, not measured, and some vendors give the distance from the lens surface, not from the end of the scope body. It can be hard to compare across vendors unless you know what they mean.

One of Leupold's great strengths is they have a generous eyebox - you can get good eye relief at a decent-sized window around the optimal eye relief point, which means you can get quick target aquisition when you bring the rifle up quickly because eye position isn't as critical. Some other scope makers are good at this too, but it takes trying them out to find out.

Also, note that the eye relief (both optimal and eyebox) changes with magnification, and willl be different as you zoom the scope. Generally, eye relief gets closer and the eyebox gets smaller as you zoom in. Some vendors (like Leupold) are starting to spec the optimal eye relief at the zoom limits.

Some scopes have a decent optimal eye relief distance, but a small eyebox at high magnifications, which means you have to hunt for a good field of view or have a very repeatable cheekweld at a given magnification. Repeatable cheekweld is a great thing, but flexibility in eye position means flexibility in fast action shooting.

For instance, the optimal eye relief for the Leupold scope you mention changes by 0.9" going from min to max zoom, so having a generous eyebox is critical to getting good eye relief at various zooms, even (or especially) when you have a repeatable cheekweld.
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