Picking a Riflescope without Losing your Mind
Some might like to say that it is far too late for me, but it isn't too late for you. It is easy to get lost in the maze of touted “features,” but like most things features do not always mean benefits. Hopefully, this little article will point up the things about a hunting riflescope that really do matter.
BRIGHTNESS
You've likely heard
all the largely meaningless terms before: “good glass, good optic,
super image quality” and so forth. Yet, fully multi-coated lenses
all function within a fairly narrow range. A large exit pupil, the objective
lens in millimeters divided by the magnification, is the biggest factor
in delivering a bright image. In Investigative Ophthalmology & Visual
Science, March 1994, Vol. 35, No. 3, exploring how maximum pupil size
decreases with age, even 67 year old eyes can dilate past 4.5 mm and younger
eyes can dilate past 5.5mm. If you want the brightest scope, you want
about 5mm exit pupil. A 50mm objective riflescope at 10x magnification
yields a 5mm exit pupil. Yet, a little 1.5-5x 32mm scope will transmit
more light, producing a 6.4mm exit pupil cranked all the way up.
Human eyes cannot recognize less than a 3% difference in brightness. In
other words, you can coat lenses all day and night, you can polish lenses,
you can scream “good glass” made from specially melted sand
retrieved from the bowels of Middle Earth all you wish. But, if you don't
have a large enough exit pupil for your eyes, you aren't getting a bright
image.
THE EVILS OF MAGNIFICATION
There are a lot of
bad things that go along with magnification for a low-light hunting scope
and hunting scopes in general. You cut down your field of view, perhaps
slowing target acquisition, and you lose the ability to see what is to
left, right, in front of, and behind your target. Most anyone can properly
place a bullet on a deer at 75 yards, with iron sights. A 10x scope gives
you that same image at 750 yards and every study I'm aware of (including
one recently completed) shows most game animals being taken inside 100
yards, with an average shot of 78 yards or so taking into account all
distances. Diminished field of view is a huge handicap for much big game
hunting. Some of the most effective snipers of WWII, the Germans, used
the Zeiss Zielvier 4x (ZF39) scope, marked in 50 meter BDC increments
to 800, 1000, or 1200 meters.
THE PERILS OF LARGE OBJECTIVES
Most of the weight in a riflescope is from its glass, the larger the objective, the more weight. To the extent that a large objective prohibits a good, instant, proper stockweld, it is a problem.
THE THIRTY MILLIMETER TUBE PROBLEM
The 30mm tube has its benefits: a much stronger tube, more room inside for internal adjustments. It also may allow lower scope mounting with a 50mm objective than possible with a 1 inch tube. It also adds weight, though, both from the scope and rings. It, like most everything, is a compromise.
THE EYE RELIEF PROBLEM
Low (close) eye relief is preferred for an EVF on a camera, binoculars, and so forth. It is also ideal for rimfire applications. On a lightweight hunting rifle, having a scope smash into your forehead due to inadequate eye relief is no fun. It is compromise again, but with significant rifle movement due to recoil, the 3.75 – 4 inch eye relief scope is an ideal range, though you are looking at the scope, rather than through it as in a low eye-relief scope.
For ballistic reticles, most commonly in the second focal plane, they work only at one power, typically cranked all the way up. That often means less eye relief, so for ballistic or hold-over reticles to be useful, they need to function with the scope cranked all the way up . . . with adequate eye-relief and exit pupil at that magnification, often 10x or 12x zoom.
THE RETICLE QUESTION
Most fully-multicoated
scopes run out of visible reticle long before they run out of usable image.
Illuminated reticles are the fix, at the expense of a bit heavier scope
and more cost. Yet, in a low contrast situation (black bear against a
dingy grey background, low-light brown deer in brown grass, and so forth)
an illuminated reticle makes it quick and easy . . . and, in some cases,
possible.
THE BALLISTIC RETICLE
Ballistic reticles have been hyped, rehyped, and over-hyped. Yet, if you know where your bullet is going to hit, why not just aim your crosshairs accordingly? Good question, as second focal plane reticles only work at one power: typically cranked all the way up. How much magnification do you want (or can you use) at sunset, or 20 minutes thereafter.
It, like most things, is personal preference. To the extent that reticles become cluttered and overly busy, I think they are a drag. However, is you hunt using “Maximum Point Blank Range” you will rarely use a holdover point at all, but when you do it will be only one notch for the most part. The longest shot I've taken on a big game animal was a running bull moose in Newfoundland. The scope used was a 2-7, and I took him at 2x magnification. Sometimes you have time, sometimes you don't. Just last year, I took a nice blue wildebeest in South Africa. After the shot, my PH asked “How far was that?” I replied, “I don't care.” Well, of course I do care, very much so, but a blue wildebeest has a large kill zone, and as long as he was inside 325 yards, it didn't matter. That was the case last year.
THE BEST THING A SCOPE DOES
What makes a scope valuable is that it holds its zero after recoil. If it doesn't hold its zero, it is worthless, regardless of brand, whether old or brand new. An old scope that doesn't hold its zero due to wild reticle float does the same thing as your new scope that doesn't hold its zero. Both are junk, not worth hunting with.
WHAT ARE SOME GOOD SCOPES?
In general, my version
of a good scope (aside from ability to hold zero) has adjustments that
do what they are supposed to, has good eye relief that is consistent within
half of an inch throughout its power range, a minimum of flaring and chromatic
aberrations, a reasonable internal adjustment range, along with the now
standard fully multi-coated lens arrays, and power rings easy to grasp
and turn.
Brand names alone don't reveal much, for most major brands have both models
that are excellent and scopes that aren't worth mounting. There are premiums
associated with “features,” but many features have nothing to
do with scope reliability, eye relief, internal adjustment range, field
of view, and field usability.
In many ways, a 6x
fixed power scope is close to the “perfect scope.” Less lenses
equal less light losses: a brighter scope. Less lenses and no erector
assembly means a light scope as well: 10 oz. or so for a fixed 6x 36mm,
always constant eye-relief and always 6mm exit pupil. If you are using
any number of 2nd focal plane variable magnification scopes, they are
fixed power scopes if you use the ballistic reticle.
The closer your variable
power scope comports to the fundamental benefits of a fixed power scope,
the better. The 2-6, 2-7, 2-8, and 2-10x power range scopes are more practical
specifications, giving you more field of view when desired, yet more magnification
for range work (2-10) and longer range hunting when desired as well. At
10x and below, often parallax is no issue and the added weight, complexity,
and cost of an adjustable objective is not wanted, much less required,
for deer hunting on up.
Copyright 2014 by Randy Wakeman. All Rights Reserved.
