Consistent rifle scope fitting

[P89DCSS]

If a rifle and scope is properly set up for me I can close my eyes, shoulder the rifle and when I open my eyes the scope is setting perfectly in my field of view. (Closed eye position test) I started thinking about this and realized for me there's a common specification that can help me set up a scope. Using this understanding allows me to have all my rifles pass the closed eye position test without trial and error.

I realized for a given rifle/scope application (target in my case) the position of my dominant eye relative to the butt of the stock and height above comb should be the same (forward of the stock's butt 7.5" and 2.25" above the comb). By using this standard eye position I can have several rifle/scope combinations and easily set up the same position on each rifle. Each rifle can pass the closed eye position test with minimal set up time/hassle. It can be measured and predicted without guessing or trial and error.

Here's what I do to locate the scope's eyepiece consistently:
- I found my preferred standard eye position by measure two different rifle/scope combo I felt were ideal (they passed the closed eye position test). The distance of the comb to scope centerline was 2.25" for both scopes and the length of pull was 14.5". When I measured the scope eyepiece distance from the stock's butt they were the same (11"). Since both scopes had similar eye relief (both had er of ~3.5") that meant my standard eye position was 7.5" in front of the rifle stock's butt.

- to summarize, i discovered my dominate eye is correctly placed for my rifle when it is 7.5" forward of the stock's butt and 2.25" above the comb (when the LOP is 14.5"). This is my personal standard eye position. If I take this into account I can easily set up a new rifle/scope combo without any guess work.

- if I located my rifle scope's centerline 2.25" above the stock's comb my scope will be at my preferred height. This is easily measured. Then I can choose the correct scope ring height to locate my rifle scope's centerline 2.25" above the comb.

- once I have the scope's centerline at the correct height, using the scope's specified eye relief I can correctly locate the scope's eyepiece in front of the rifle stock's butt. I add the scope's specified eye relief to my standard eye position to located my scope's eyepiece in front of the stock's butt. (for me 7.5" + ER)

Make sense?

I set up two new rifle/scope combos using this technique and now they're passing the closed eye position test. Before I figured this out I was struggling to get things correct.

 

[JDGray]

Different shooting positions come into play. Prone shooting and shooting off a bench, matters on where you mount your scope.

 

[P89DCSS]

Different shooting positions come into play. Prone shooting and shooting off a bench, matters on where you mount your scope.

Agreed. The method I described allows the shooter to note the scope position on one rifle and use the knowledge to position a scope on a second rifle for any shooting stance, prone, bench or whatever is chosen.

 

[rbernie]

There is enough variability in eye relief across my optics that I find that I have to vary the formula quite a bit in terms of fore/aft positioning.

 

[jmr40]

Yea, the scope matters.

Eye relief can be measured, but "eye box" is a lot harder to define. Eye relief is the maximum distance your eye can be from the back of the scope and still be able to see clearly through it. Eye Box is the range of distances where your eye can see through the scope. Many scopes have a very limited eye box. Meaning getting the scope adjusted properly is critical. Too close or to far back and you can't see though it unless you move your head back and forth on the stock to get in just the right position.

Others have a much bigger eye box. Meaning you don't have to be as exact in getting it mounted in the right spot. This way it will still work if you're wearing a T-shirt or if you're bundled up for sub zero weather.

With most scopes the magnification matters too. Not all, but most variable power scopes will be more forgiving on lower magnification settings than the higher magnifications.

Of the major brands Leupold traditionally is one of the most forgiving scopes in regards to eye relief and eye box. There are a lot of folks who will argue there are better scopes for the money optically, but this is a big part of why they remain popular with hunters.