Download The Importance of Eye Relief

The Importance of Eye Relief
This article is not about the
product Visine, although I may
need some by the time that I
finish this article.
Note that this article is about scopes; rifle, handgun, or
shotgun – no matter. The right scope, with the correct eye
relief, not only can keep you safe but increase accuracy on
whatever it is mounted. Dot sights and Holographic sights do
not suffer from eye relief and this is the only mention that
they receive in the article.
The impetus for my writing this article stems from a recent
experience in mounting a scope on the Ruger 77/357; a carbine
bolt-action rifle chambered for the .357 magnum round. There
is nothing special about the rifle and; therefore, I expected
nothing special about a scope that it was to be adorned. I was
wrong about that.
The Ruger 77/357 comes with a 13.5-inch length of pull (LOP)
and the synthetic stock is like many found on other rifles.
There is nothing special about the stock, but the lengths that
I went through to fit the right scope to the rifle was more
than I bargained for.
I was using the scope mounting rings that Ruger provided with
the rifle. They are about medium in height and a scope with an
objective lens housing of 40mm to 44mm would be ideal. I did
not feel that I needed a lot of magnification for a rifle that
shoots a pistol cartridge and decided that the Bushnell Banner
Dusk til’ Dawn 2-7x 32 shotgun scope would be ideal for the
rifle and me.
My first trip to the range with this combination proved to be
a disaster. I could not get far enough up on the rifle to
obtain a proper scope picture and the target results only
added to my frustration. I was not only fighting the eye
relief of the scope but a hard trigger pull; both of which I
could fix.
I opted to try a different scope of a different magnification
level, which normally means that the eye relief would be
greater. I mounted a Cross Point Adventure Class 3-9×40 scopes
and everything seemed fine – at home. Again, at the range, the
eye relief was slightly better than the previous scope.
Although I did shoot better, the scope was obviously not for
me.
I found a Bushnell Banner 3-9×40 scope with a 6-inch eye
relief and decided to give it a try. The results were
spectacular at the ocular lens. I simply laid my head on the
stock, opened my sighting eye and a perfect scope picture was
evident. My problem was solved with this scope. A subsequent
trigger was performed on the rifle by my favorite and highly
competent gun smith and the rifle is now ready for whatever
comes in front of it.
I have 3-9×40 scopes on most of my high-powered rifles so I am
no stranger to the scope. Like LOP; however, I am learning how
little things can affect how you operate a long gun. With that
in mind, let me pass on some information about scopes and eye
relief.
Eye Relief
Distance
=
Ocular
Eye relief for an optical device is simply the distance from
the ocular lens of the optical device to your eye. While eye
relief is not a big thing with binoculars, it is with scopes
due to the recoil characteristics of most firearms. A large
caliber firearm will generate more recoil. Greater recoil
means that the scope on a rifle (or shotgun), the greater the
distance that the scope moves rearward with the rifle under
recoil. If the eye relief of the scope is too short, you may
be gifted with the ‘scope eye’ award when the rim of the
ocular lens housing makes contact somewhere around the eyebrow
of your sighting eye. If you wear prescription glasses, the
eye relief of a scope becomes problematic as you try to
balance the eye relief of the scope against your distance to
the scope. The secret is ‘move the scope to the eye and not
the eye to the scope.’ There is; however, one exception to
this general rule that I will bring out later in this article.
If your eye is too far from the scope, the ocular lens will
look fuzzy and the scope picture will be reduced. This is true
of any scope – even intermediate and long eye relief scopes
(I’ll touch on them shortly).
CZ 527 w/Scope
Long Eye relief (LER) Scope
Mounted on a Ruger Gunsite
Scout
Shotgun-Mounted
Long
Eye
Relief (LER) Scope
Most scopes are manufactured with a 3-inch to 4-inch eye
relief. Long eye relief (LER) scopes, like those found on
‘Scout’ rifles are considered long eye relief scopes; whereas,
the eye relief can be anywhere from 8-inches to 10-inches
(sometimes greater). The Bushnell Banner 3-9×40 scope with a
6-inch eye relief would be considered a intermediate eye
relief (IER) scope and these types of scopes are usually found
on higher end scopes.
I recently mounted a Center Point 4-16×40 scope on a Ruger
American in .223 caliber and the eye relief and scope height
was near perfect. Go figure!
Personally, I do not like scopes. Many hunting rifles make
their use necessary. They do add weight to the firearm, which
in some cases is not a bad thing. With eye not as sharp or as
light-gathering as they used to be, I have finally succumbed
to ‘scoping’ whenever possible and using dot-sights more often
than not on long guns.
on several rifles and
scopes that I use with
on open sights for my
medium distances.
I do have long eye relief (LER) scopes
pistols. These are low magnification
both eyes open. However, I still rely
EDC and other handguns for short to
For rifles and shotguns where a scope is mounted above the
receiver, a standard or intermediate eye relief scope may work
well for you. A rifle or shotgun upon which is mounted a scope
forward of the receiver, a long eye relief (LER) scope would
be the choice to use.
A Properly Mounted Scope
A long eye relief scope spares the shooter the risk of injury,
and also can make it easier for the shooter to locate the
target. While scopes with a short eye relief require careful
positioning of the shooter’s head, scopes longer eye relief
offer a range of positions. The shooter only has to get his
eye into a range of distances, far enough from the scope to be
safe and close enough to be within the eye relief distance.
To adjust the scope for the correct eye relief, place the
scope inside the rings, as it will sit on top of the gun, but
do not tighten the rings. Move the scope in or away from your
face to estimate where the correct placement will be to give
you the correct eye relief. Adjust the scope to provide the
best ‘medium’ distance from standing, sitting (bench
position), and prone positions. Normally, your face will be
closest to the scope while prone and further rearward when
standing. Note that the scope need not be level to do this;
you are simply trying to find the best relationship between
the scope and your eye.
Lightly snug one scope ring screw to hold the scope in
position while you transfer the rifle to the sighting vice.
Then, mark the correct position on the rings with washable
highlighter ink. Loosen the screw that was holding the scope
and once you have ‘level-level-leveled’ the rifle and scope,
start the scope ring tightening process. You may wish to
double-check the scope position while doing so to ensure the
scope position remains at the mark you added earlier. Finish
tightening the scope rings to the correct torque and your
scope should be ready for bore sighting.
Adjustable Stock Allows the
Operator to ‘Move’ to the
Scope
Earlier in the article, I mentioned one exception to the rule,
‘Move the scope to the eye and not the eye to the scope.’ This
exception would be for rifles that have adjustable stocks; for
example, the AR-based MSR and some shotguns intended for
tactical use. The operator of the adjustable-stocked firearm
can adjust the stock in or out to obtain the correct scope
picture and eye relief regardless of whether the scope is
mounted rearward, over the receiver, or forward of the
receiver in a ‘scout’ configuration. I found that I needed to
move the stock in one notch to correctly position my eye to
the 3-9×32 tactical scope mounted on QD mounts.
If you want (or need) to mount a scope on a long gun (carbine,
rifle, or shotgun) or even a handgun, magnification power is
not all that you should be thinking about. A scope that is
incorrectly fitted to your eye cancels the magnification power
of any scope. Determining the eye relief is as important as
the mounting, alignment, and magnification power.
A key point to remember is that the eye relief is the
‘maximum’ distance from the ocular lens to your eye to obtain
the proper scope picture; you can be closer than the maximum
distance.
Another point to consider is the use of a recoil pad. I use a
recoil pad on high-recoil long guns (normally to obtain the
LOP that I need). A recoil pad normally adds 1″ to the LOP.
Sometimes I use a recoil-shield in lieu of a recoil pad. If
you use any of these devices while shooting, adjust the scope
with these devices attached. Even if you do not use these
devices, your eye will be within the eye relief maximum
distance. Just be aware that, in most cases, you will need
about 3 inches from scope to eye. For most rifles and
shotguns, this distance will be adequate; and you will not be
crowding the scope and becoming the possible bearer of the
‘scope eye’ award.
The following provides a couple of videos on the subject of
scopes:
https://www.youtube.com/watch?v=qUudK3qJdTQ
https://www.youtube.com/watch?v=gg4wXa5UmHY