Picking a Hunting Riflescope Without Losing Your Mind
Some might 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 actually matter.
BRIGHTNESS AND EXIT PUPIL
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 1.5-5x32mm scope will transmit more light, producing a 6.4mm exit pupil at 5x.
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. However, if you don't have a large enough exit pupil for your eyes, you aren't getting the brightest 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, 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 stock weld, it is a problem.
THE THIRTY MILLIMETER TUBE
The 30mm tube has its benefits, primarily more room inside for internal adjustments. It adds weight, though, both from the scope and rings. It, like most everything, is a compromise.
Short (close) eye relief is fine for rimfire applications. On a powerful, centerfire 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, around 4 inches of eye relief scope is an ideal range. However, you are sort of 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 at its maximum magnification, with adequate eye-relief and exit pupil at that magnification.
THE RETICLE QUESTION
Most fully-multicoated scopes run out of visible reticle long before they run out of usable image. Illuminated reticles are the answer, at the expense of a bit heavier scope, battery dependance and higher 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, easy and, in some cases, possible.
THE BALLISTIC RETICLE
Ballistic reticles have been hyped, re-hyped and over-hyped. 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, if you hunt with a rifle zeroed for its Maximum Point Blank Range you will rarely use a holdover point at all and if you do it will be only one notch.
The longest shot I've taken on a big game animal was a running bull moose in Newfoundland. The scope used was a 2-7x 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, but a blue wildebeest has a large kill zone and as long as he was inside 325 yards, it didn't matter, because my rifle was zeroed for the MPBR of the cartridge and load I was using. That was the case last year.
THE BEST THING A SCOPE DOES
The most important thing a scope does is put the point of aim (the reticle) and the target in the same optical plane. 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 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.
WHAT ARE SOME GOOD SCOPES?
In general, my version of a good scope (aside from ability to hold zero) has accurate adjustments that do what they are supposed to, adequate eye relief that is consistent within half of an inch throughout its power range, a minimum of flaring and chromatic aberrations, reasonable internal adjustment range, along with the now generally standard fully multi-coated optics and power rings easy to grasp and turn.
Brand names alone don't reveal much, for most major brands (especially the lower priced models) have scopes 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 usability in the field.
In many ways, a 6x fixed power scope is close to the perfect scope for open country big game hunting. Fewer lenses equal less light losses and a brighter scope. Fewer lenses and no erector assembly means a light scope, as well, usually around 10 oz. or so for a fixed 6x36mm. The eye relief is always constant and the exit pupil is always 6mm. If you are using a second focal plane variable magnification scope, it becomes a fixed power scope when you use the ballistic reticle.
The closer your variable power scope comports to the fundamental benefits of a fixed power scope, the better. The 2-6x, 2-7x, 2.5-8x and 2.5-10x magnification scopes are practical specifications, giving you more field of view when desired, yet more magnification at the rifle range and for the rare long range shot at a big game animal, when required. At 10x and below, parallax is usually not an issue and the added weight, complexity and cost of an adjustable objective is not required.
Copyright 2014 by Randy Wakeman. All rights reserved.