Optics
Choose the Right Scope
By Ron Spomer
A version of this article first appeared in Minnesota Outdoor News
Whether you shoot a handgun, slug gun, muzzleloader or centerfire rifle, you’ll shoot more effectively with a telescopic sight. Scopes magnify the target, which reduces identification error (doe or spike?) They also place the magnified target and sight (crosshair) on the same plane of focus so both are sharp.
Whether you shoot a handgun, slug gun, muzzleloader or centerfire rifle, you’ll shoot more effectively with a telescopic sight. Scopes magnify the target, which reduces identification error (doe or spike?) They also place the magnified target and sight (crosshair) on the same plane of focus so both are sharp.
Most shooters buy too much scope and pay too little for it. The bigger and more powerful a scope, the more precisely and durably it must be built to transmit a clear image and stay in one piece. Recoil, especially from hard kicking slug guns and muzzleloaders, breaks cheap scopes quickly.
While there are no hard and fast rules governing price/value in scopes, those selling for less than $100 are generally of poor optical quality and designed to withstand the recoil of small calibers from .223 Remington to perhaps .30-06. Recoil damage is cumulative and inevitable. The more shots fired, the sooner the scope will fail. A lens will break from its mooring, the erector spring will weaken or break, the reticle will turn with the torque of the gun. It’s been said inexpensive scopes are designed to withstand about 1,000 to 1,500 shots, more than the average deer hunter will take in a lifetime. If you’ll shoot more than that, or shoot a hard-kicking gun, consider spending at least $200 to $400 for a scope (discount prices.) Above $400 you are paying for better optical quality and light transmission, also called brightness, along with increased durability and dependability.
Cheap scopes are usually dim with poor image quality and low contrast. Huge objective lenses don’t correct this. Aim such a scope into the shadows toward the setting sun and you’ll see a lot of glare and haze which obscures your target. It’s the diameter of the circle of light leaving the eyepiece – called exit pupil – that matters. Exit pupil (EP) grows with a larger objective lens, shrinks with magnification. Divide objective diameter by power to get EP. A 50mm diameter objective lens at 4X has a 12.5mm EP, roughly twice as bright as your pupil can take in. But at 10X this EP shrinks to 5mm, about as wide as a 50-year-old’s pupil can dilate.
A 4mm EP in a scope provides all the light you need to see crosshairs on most game in legal shooting light, and 10X is all the magnification you need to target big game out to 1,000 yards (it’ll look as if its 100 yards away.) No one has any business shooting game at 1,000 yards, and darn few of us should try it at 500 yards. Coyotes and varmints, maybe, but not deer. A basic 4X scope is sufficient for deer to 400 yards. More power can help for precisely aiming at a standing target from a solid rest, but isn’t mandatory. Why unbalance your gun with a bulky and heavy scope you don’t need? Why pay for it? A 3-9×40, 2.5-12×40 or perhaps a 4-16Xx42 should be all you ever need unless you specialize in extreme range varminting or target shooting.
More important than ultimate brightness is consistency. That crosshair should stay where you adjust it shot after shot, season after season. Many manufacturers use the same mechanical parts in their mid-priced and highest priced scopes – only lens quality differs.
Glass quality rarely changes from scope to scope. A handful of manufacturers make all of it. An engineer specifies a type of glass, not its quality. What makes one lens “better” than another is how accurately it is ground, polished, matched to others and coated to resist reflection loss. Anti-reflection coatings are your biggest bang for the buck in scope brightness and clarity. Un-treated glass reflects about four percent of the light the strikes it, another four percent that exits, or 8 percent per lens. Some variable scopes harbor 8 lenses. That’s an 64 percent light loss! Coating each air-to-glass lens surface with a single layer of anti-reflection coating knocks this loss to about 2 percent. Adding more coatings (multi-coating) can reduce loss to .5 or even .2 percent. This is a huge increase in light transmission with no added size or weight. Spend your money on anti-reflection coatings, not huge objective lenses.
Fixed power scopes are ideal choices for short-range handguns, slug guns and muzzleloaders. For shooting to 100, even 200 yards, a 4X is perfect, giving a wide enough view for extremely close shots and enough magnification for the longest shots. Experienced 4X shooters have routinely made 300-yard to 500-yard hits on game. Because fixed power scopes have fewer lenses and moving parts, they are brighter and more durable than variables.
In an all-round deer/elk rifle a 2-7X or 3-9X with 36mm to 40mm objective will handle everything from whitetails flushing at 15 yards to elk standing at 400 yards. On a combo deer/coyote/varmint rifle in .243 Win. or .25-06 Rem. you might put up with a big 4.5-14X scope if you do considerable long range varmint shooting. It will be a bit heavy and cumbersome for deer hunting, especially in woods. Reserve the huge 6-20X and bigger for dedicated target and varmint rifles.
There’s much more to scopes than the above (like parallax, eye relief vs. field-of-view, the myth of the 30mm main tube, anti-fog coatings, the value of guarantees, etc.) but you won’t go wrong with the above recommendations.