"The eye box on this scope is too tight at high magnification."
"I can't use the scope at max power."
"I can never find the eye box."
We hear these statements often in regard to Low-Power Variable Optics with high magnification ranges, like the modern 1-8x or 1-10x options. It's a common complaint toward LPVOs or optics with high zoom ratio. Manufacturer tradeoffs in magnification range or other optical features can result in an optic that is harder to get behind.
Do you shoot with an LPVO? Learn more about using the reticle more effectively for precision shots!
But what is the eye box? It's not a specification listed by any scope manufacturer, so how can we measure or compare it to other optics?
Put simply, the eye box is combination of eye relief and exit pupil, both of which are measurable and listed specifications that you can find for any optic you're interested in.
Eye Relief: The distance from the ocular lens to the eye, where the sight picture or field of view is full and complete.
Exit Pupil: The circular beam of light that enters the eye.
The pupil of the shooter's eye must be within the exit pupil of the optic in order to see the sight picture. We can spend a lot of time discussing exit pupil and how it's measured, but there are a few key things to note about this specification in regard to the eye box. Firstly, the diameter of the exit pupil decreases at higher magnification. This is one reason it's harder to find the eye box at high magnification. Secondly, a larger exit pupil relates to a brighter image. This is why the picture gets darker at high magnification.
When we combine the values for eye relief measurement and exit pupil diameter, we can measure where the eye box will be located. It's important to note that the eye box will get bigger at lower magnification and smaller at higher magnification because the exit pupil and eye relief will change as the user rotates through the zoom range. This illustration shows that the eye box has a diamond shape when shown in 2D, but in reality it is more of a double cone shape in 3D. In order to see the full image without scope shadow and to reduce parallax as much as possible (LPVOs typically have a fixed parallax), the shooter's eye must stay within the very small eye box of the LPVO.
"So how can I find the eye box every time, without searching?"
This is the question that shooters should be asking whenever they discover they are having trouble with their optic or rifle set up. It's tempting to blame the optic for poor performance, but remember that the magnification range you were attracted to when purchasing the optic comes at the price of a smaller, less forgiving eye box.
We know that searching for the eye box is a frustrating experience, especially when you're on the clock. Setting up your rifle with the correct Length of Pull, mount height, and scope placement on the rifle will set your eye up for success.
Length of Pull: The distance from the face of the trigger to the end of the stock.
Finding the right Length of Pull can be explained or described in multiple ways, but the one we like best here at Sun and Shadow is adjusting the distance of your stock to get the wrist on your firing hand as straight as possible while still keeping your shoulders perpendicular to the gun (If you'd like to learn more about why we describe it this way, please see our article on Natural Point of Aim where we discuss more about Length of Pull).
After setting the Length of Pull, set the scope at max power and place the scope on the rail to where you can see the eye box when you are comfortably situated behind the gun. It's important to bring the scope's eye box to you, rather than change your body position to meet the scope. Once you've found the position where you're comfortable behind the gun AND you can see the eye box at max power, then you can tighten the scope's mount down onto the top rail.
Ultimately, building consistency in your head placement, through build-and-break drills and positional dry fire, is the best way to get into the eye box quickly.
However, if you're still having trouble, a cheek riser can help. A cheek riser will elevate your eye closer to the center axis of the eye box. Using the cheekbone as an index point, rather than the meat of the cheek or jaw as we often see with stocks common to the AR15/AR10, will give your face a smaller target to shoot for when you're entering the eye box. A cheek riser can allow you to index with the smaller cheekbone, rather than the larger surface area of the cheek, leading you to a more precise head placement along the stock.
Our Carbine Cheek Riser was built to fit a wide range of stocks, and our SOPMOD and SBA3 Cheek Riser lines were tailored to work with more specific models. We build these risers in multiple heights, which will allow you to fine-tune the fit that's right for your face, rifle, and optic. We make risers intended for scoped rifle shooting, red-dot shooting with elevated optics, and night-vision set-ups.
See how our cheek risers will help you find the eye box every time.
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