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This Thing Called Eye Relief

This Thing Called Eye Relief

With “magnum eye” reaching epidemic proportions, there’s no reason to ignore eye relief anymore.

By Ralph M. Lermayer

Perhaps no part of a riflescope’s specifications is less understood than eye relief. Many hunters don’t have a clue what their pet scope’s eye relief is, nor do they care. As long as they can bring Ol’ Betsy to the shoulder and instantly find hair in the scope, it’s perfect.

Eye relief is the distance from the rear lens your eye requires to see a full picture. The industry average for a fixed-power scope is about 3 1/2 inches. For most variables, you’ll start out about there at the lower power, and about 2 1/2 inches when you crank up to to max magnifcation. The lower number is often hidden on the spec sheets of variable scopes, with only the easy-to-live-with, higher number listed. Others provide both numbers so you know what to expect when the scope is cranked up to the highest power.

Until recently, that average range worked just fine. The shift was minimal with the most popular 3-9x scopes, You might have to fidget your head a bit to get a full picture at 9x, but it wasn’t much.

In the past, extremely hard-recoiling rifles wore a 2x scope or no scope at all. The real high-magnification stuff was found on light-kicking, small-bore target or varmint guns.

Not so today. Now we have a host of magnums, from shorts, super-shorts and full-house Maggie’s shorts — harder-kicking choices that deliver serious recoil and reach a lot farther, and they’re being paired with much higher-powered variables. Add to that the insanity being promoted by some writers to make a sport out of killing deer and elk at 500-plus yards, and we’re seeing more and more shooters with bleeding third eyebrows. Magnum eye is reaching epidemic proportions today.

What we need, and what could easily make the difference in sales success or failure for all scope manufacturers is to take that 3 1/2-inch standard, toss it in the trash and make 4 to 4 1/2 inches of constant eye relief the new standard. It’s actually a simple thing to do, yet none of the major scope manufacturers have done it.

This Thing Called Eye ReliefA Tale of Two Numbers

To understand why manufacturers are holding on to the 3 1/2-inch standard, you need to look at another often-ignored number on the scopes’ spec sheets. It’s called field of view. Usually given in feet or meters at 100 yards, it tells you how far you can see from edge to edge at that distance.

To explain, let’s suppose your scope had a field of view of 100 yards at 100 yards. (Put the phone down, I know it’s impossible; I’m just illustrating.) Then, if a target was standing on the 50-yard line, and you placed it in the center of the scope, you would see both goal posts on the sides of the image.

In reality, this number is actually closer to 40 feet on the low end, squeezing down to 20 feet or less when you crank up the dial. Because of the laws of optical physics, when you increase the eye-relief distance, you shorten the field of view. That’s a tradeoff I will gladly accept, yet one the white coats are hesitant to make.

When I’m looking at a target at 100 yards, whether I can see 40 or 35 feet from side to side is not a real-world factor. For fast acquisition of targets in close, the field of view is more than adequate under 100 yards, and, when I’m settling in for a long shot where the tighter number at the higher power is a factor, I have plenty of time to locate and center the target.

To further illustrate the interaction, let’s look at two designs with a tremendous amount of built-in eye relief. Handgun scopes are designed to be held way out there, almost 24 inches from the eye. Anyone who’s ever used a handgun scope knows how critical head and eye position are. I have one that actually goes up to 7x. It is almost useless at that power. Unless I’m on a solid rest, it takes sheer luck to get a fast, full image. Handgun optics are best served at 1x or 2x for practical hunting.

The other extreme design is the scout scope, designed to be set about 12 to 16 inches from the eye in the middle of a rifle barrel. What they never tell you about this bizarre design is that the farther your eye is from the scope, the faster you lose light transmission. In other words, with a Scout setup, those low-light conditions early and late in the day are lost to those with a scope that far down the barrel. Excessive eye relief does come with drawbacks, but going from 3 1/2 to 4 1/2 inches won’t cause any loss of brightness that will affect real-world performance.

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We are beginning to see changes, although in most cases, the manufacturers were forced into it. Shotgun slug hunters who shoot megaweight loads have forced the issue, as has the inline muzzleloading community. Responding, Nikon has released the Monarch muzzleloader and shotgun line as well as modifying the entire new Monarch line to an almost constant eye relief of 4 inches throughout the entire range. Even the big 4-16x and 5-20x scopes only drop to 3.6 inches at the long end. These are bulldog-tough, crystal-clear optics that are very forgiving and pop into full view even when you’re scrunched on the stock.

Bushnell has long offered a 3-9x scope with a full 6 inches of eye relief in the Banner line. These are currently housed on my slug barrels and have shown no problems after hundreds of monstrous-recoiling rounds. They give up a little light, but they take the beating, and I don’t have to crawl up on the scope to get a full picture. The little-appreciated Simmons A-Tec line also offers a constant 4 inches throughout the power range, and grudgingly, others are following suit.

If you’re packing a magnum and want to put a lot of scope on it, make a little study into the available eye-relief numbers before you commit. If it isn’t 4 inches or more, pass. If you insist on staying with the lower numbers, be sure to bring lots of Band-Aids.

Reprinted from the October 2007 issue of Buckmasters GunHunter Magazine. Subscribe today to have GunHunter delivered to your home.

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