What is Eye Relief on a Scope and How To Correctly Adjust it

What is Eye Relief on a Scope? Having incorrect scope eye relief is not only annoying - it can be can also be hazardous. Is your riflescope positioned for correct eye relief? Not sure? Better check it. Read how to correctly adjust scope eye relief here.

Is the eye relief of your riflescope set correctly?

Seeing the whole field of view (FOV) when you aim through your scope does not always mean that eye relief is set correctly. 

You may actually be craning or scrunching your neck to compensate for an incorrectly positioned scope without realizing it.

Do not conform to your scope. No; adjust that scope so it conforms to you instead.

Is your riflescope far enough forward to allow your rifle to recoil without gashing your eyebrow? Check it before you shoot. Do not learn the hard way that is not.

What is Eye Relief on a Scope

The eye relief of a gun scope, as well as other optical devices, is the distance from the ocular lensa viewer's eye must be to see the full field of view. 

The ocular lens is the closest lens of a optical device to the viewer's eye. There is a maximum and a minimum eye relief at which the viewer can see the full FOV.

Does seeing the full FOV always mean scope eye relief is set correctly-1

Does seeing the full FOV always mean scope eye relief is set correctly-1

If the viewer's eye is too close to the ocular lens, the viewer will see a "shadow" around the perimeter of the FOV. (It is not actually a shadow, but that is how it will be referred to here.)

Similarly, if the viewer's eye is too far from the ocular lens, the viewer will also see a shadow around the perimeter of the field of view. Therefore, eye relief actually has a range.

The whole field of view will be visible only if the viewer's eye is within the eye relief range.

Pick up your riflescope and remove the lens caps. Hold the scope about one foot or so in front of your viewing eye. View a well-lit, light-color wall.

Can you see the whole field of view? Probably not.

Do you see a shadow around the perimeter of the FOV instead? Well, that is what you should not see when you view through the scope after it has been mounted on a rifle. 

If you move the scope too close to your eye you will see a similar shadow.

You must adjust eye relief to eliminate all of that perimeter shadow. Eye relief is adjusted by sliding the scope forward or backward in the scope rings before it is clamped by tightening the ring caps.

You can watch the following video for a clearer view of "What is Eye Relief on a Scope":

What is Riflescope Eye Relief

Now you clearly know about What is Eye Relief on a Scope. And next you will ask yourself: How is riflescope eye relief different from other optical device eye relief? What is a good eye relief for a rifle scope?

All optical device users must be concerned with FOV perimeter shadow.

However, a shooter must be even more concerned with eye relief for another reason - recoil. 

Eye Relief

Eye Relief

The eyepiece rim will impact the shooter's eyebrow during recoil if the eye relief is too short.

In severe cases, the eyepiece rim will gash the shooter's eyebrow.

Therefore, gun scopes are designed with longer eye relief than most optical devices - between 3 inches and 3+5/8 inches depending on the model. (Handgun scopes have a much longer eye relief than even riflescopes because they are normally aimed at arms length.)

Yes, dealing with FOV perimeter shadow is frustrating. Dealing with recoil if eye relief is too short is hazardous.

Correct eye relief helps a rifle shooter shoot better. 

Not enough eye relief

Not enough eye relief

A shooter will be able to establish a comfortable, consistent, and solid stockweld whenever he or she does not have to crane or scrunch his neck to accommodate incorrectly adjusted eye relief.

Also, in addition to recoil, anticipating painful eyebrow gash will cause some shooters to hesitate and flinch. Hesitation and flinch are both detrimental to good shooting.

Correctly adjusting eye relief to prevent eyebrow impact will eliminate one of the factors may cause hesitation and flinch.

Scope magnification affects eye relief. 

With all other optical factors equal, an increase of magnification results in both closer minimum eye relief and closer maximum eye relief. i.e. not only does eye relief decrease with increased magnification, but eye relief range decreases as well.

Eye relief becomes shorter when you turn up the power of a variable-power scope.

Image shooting a heavy-recoiling rifle while aiming through a high-power scope with its short eye relief. Yes, eyebrow gash!

Too much eye relief

Too much eye relief

That is why heavy-recoiling rifles and high-power scopes are not compatible.

Do not be overconfident and try to shoot a heavy recoiling rifle with a high-power scope.

Even with the relatively long eye relief, riflescope eye relief should be set almost to the forward limit of its range to provide additional space for recoil.

Adjusting Eye Relief

You must adjust eye relief to fit yourself. In addition to the length of the buttstock, the length of your neck, the thickness of your shoulder, and the shape of your cheek affect your eye position relative to the scope.

There is not much you can do to physically change yourself. So adjust the scope's position to fit you.

Well, then, how can you adjust eye relief correctly? How to measure eye relief for a scope?

First, be certain the rear scope ring is as far forward as possible. 

That means it should be as close as possible to the rifle's eject port without actually being over the ejection port. Reorient the rear scope base of two-piece scope base if you must so the rear ring can be attached farther forward.

The rear ring should be in the cross-slot closest to the ejection port if the base is a one-piece cross-slot base.

You must slide the scope within the rings to adjust eye relief. 

Loosen the screws that hold the ring caps (the top half of the scope rings) over the scope tube.

Since you should set eye relief close to its forward limit, slide the scope as far forward in the rings as power adjustment ring or ocular lens bell will allow.

Will you be wearing heavy clothing when you hunt? Will you be wearing a recoil shield? The thickness of your coat will affect eye relief. So will a recoil pad.

Put the heaviest clothing on you will be wearing when you go shooting before you adjust eye relief.

Remove the lens caps. Set the power at its highest magnification if the scope has variable power. The highest power setting will provide the shortest eye relief range. You can check eye relief for the lowest power setting later if you have a variable power scope. Do not be concerned with focus or leveling the reticle yet.

Your shooting position will affect head position along the stock, therefore, your shooting position will affect eye relief.

Your head will normally be farther forward on the stock in the prone position than in the sitting or standing position so adjust eye relief in the prone position if you expect to shooting in the prone position.

You can check and readjust eye relief for the sitting and standing positions later if you need to. Adjust eye relief in the sitting or standing position first only if you never expect to shoot from the prone position.

With the rifle unloaded and on 'SAFE', pick up the rifle, point it at a light-colored featureless wall, close your eyes, and assume your shooting position.

Do not crane or scrunch your neck. Just assume a comfortable shooting position.

You must adjust the eye relief to fit you; do not adjust you to fit the eye relief. (Are your eyes still closed? They are? Then how are you reading this? Close your eyes!)

Relax. Maintaining that comfortable shooting position, establish a good stockweld. 

Do not change your head position; just open your aiming eye.

Attempt to view through the scope. What do you see? Do you see the whole FOV clearly or do you see a shadow around the perimeter? Maybe the FOV appears all black.

Whether you saw the whole FOV clearly or not, slide the scope rearward (toward you) 1/8-inch. There should be at least 1/8-inch between either the power ring or the objective bell lock ring depending whether the scope has variable-power or fixed-power and the rear scope ring anyway. 

Close your eyes, assume your preferred shooting position again, relax, and get a good stockweld.

Without changing your head position, open your aiming eye. What do you see now? You will know that sliding the scope toward you is the correct direction if the shadow disappeared or became thinner. You have more work to do if the whole FOV remained (no shadow), a perimeter shadow appeared, or the shadow became thicker.

Stop for now if there was a thin perimeter shadow that disappeared after you slid the scope 1/8-inch rearward.

However, if the shadow is still there but appears thinner, slide the scope another 1/8-inch rearward and check eye relief again.

Remember, do not change your head position to attain the full field of view. Close your eyes each time before you establish a stockweld so your are not tempted to crane or scrunch your neck.

Continue sliding the scope rearward in 1/8-inch increments and checking until you do not see any perimeter shadow - none at all.

Check the eye relief at least three times but as many you need to be certain there is no shadow.

When the scope is at a position where there is no perimeter shadow, slide it rearward one additional 1/8-inch.

At this position the scope should be about 1/8-inch within the forward limit of the eye relief range.

That is about where it should be; not quite to its forward limit. 

That 1/8-inch or so of leeway is available if you have to take a quick shot and do not get your cheek positioned perfectly on stock, if you assume a shooting position other than the one you adjusted eye relief for (such as an awkward shooting position you must assume to take a shot while hunting), or if you wear thinner clothes than you wore when you adjusted eye relief.

What if the full FOV remained or the perimeter shadow appeared thicker after you slid the scope rearward the first 1/8-inch? In that case there is not enough scope eye relief even with the scope slid all the way forward. (The rear ring is in its most forward position behind the ejection port, isn't it?)

You could lengthen the pull if the riflestock has an adjustable pull.

If the stock does not have adjustable pull, you could install a thicker recoil pad or install a shim between the currently installed recoil pad and the buttstock that matches the contour of the buttstock.

A third alternative, if the scope base is a one-piece tactical (Picatinny) base, is to move the rear scope ring one more cross-slot forward.

This alternative is least suitable because in that cross-slot the scope ring may interfere with cartridge loading and ejecting and it does nothing to make the riflestock fit you better.

Whichever alternative you choose, slide the scope all the way forward to the ring then slide it rearward in 1/8-inch increments to adjust eye relief as described above.

You should check eye relief in the sitting and standing positions if you initially adjusted eye relief in the prone position.

That is if you expect to shooting in either of those positions. Maybe you will have to slide the scope an additional 1/8-inch rearward to see the full FOV in sitting or standing position; maybe not. Now is the time to check.

After you have the eye relief adjusted at the highest magnification, turn the power down to the lowest magnification if it has variable power without disturbing the scope's position. 

Again, assume your preferred shooting position, close your eyes, relax, and get a good stockweld.

Without changing your head position, open your aiming eye. Do you see any shadow with the power at its lowest setting? Probably not; there will be even a wider eye relief range at the lowest power setting than there was at the highest power setting.

Wrap two strips of electrical tape around the scope tube

Wrap two strips of electrical tape around the scope tube

Eye relief is correct if you do not see any shadow at both the highest and the lowest power levels. 

Careful; do not move the scope.

Put the lens caps on.

Remove the ring half screws and the ring caps being careful not to disturb the scope. Leave the scope in the ring saddles.

Cut two strips of 1/2-inch wide electrical tape; each 3+1/8-inch long if your scope has a 1-inch main tube or each 3+5/8-inch long if your scope has a 30mm tube. (Black electrical tape goes well with a scope that has a black surface finish. White electrical tape looks better on scopes that have a silver finish.)

Stick one strip of tape on the scope main tube precisely where each of the ring saddles is located. 

Pick up the scope and wrap each strip of tape all the way around. It's okay; the tape will mark the eye relief position now.

You can leave the tape around the scope tube unless it interferes with scope ring fit around the tube.

Place the scope back into the ring saddles. Align the electrical tape with the rings. Place the scope ring caps in position and install the screws. Be sure to level the reticle before you tighten the screws.

Readjusting Eye Relief

Eye relief is set after you tighten the ring screws. You are done - for now, anyway.

Are you still growing? You should readjust eye relief every six months or so if you are still growing.

If you do not, the scope eyepiece rim may unexpectedly gash your eyebrow during recoil someday because eye relief got shorter as your neck grew longer.

Do not check and adjust eye relief only when you initially mount a scope. Other circumstances also call for eye relief check and adjustment.

Check and adjust eye relief after transferring the same scope to a different rifle, after mounting a different scope on the same rifle, or after installing a different type of scope base on the same rifle.

Buttstock pull varies among rifles, another scope may have different inherent eye relief, and not all types of scope bases position the rear ring the same. Each of those factors affect eye relief.

Failing to adjust eye relief correctly when you mount a scope and failing to readjust it after making a change is not only frustrating - it can also be hazardous! So adjust that eye relief.

Now you know how.

Thanks for reading and I hope you found this article about "What is Eye Relief onhelpful. If you have any questions or comments please feel free to leave them in the comments section below.

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3 thoughts on “What is Eye Relief on a Scope and How To Correctly Adjust it”

  1. Thanks for this great article for eye relief. it is very helpful for a beginner like me. After reading this I think I am able to understand what is eye relief and how can i use it

  2. hello is it the same for air guns
    wot size scope should i use for shooting under 50 yards
    good article 75 years old but still learning

    hope you can help peter leonard

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