Advancements in Rangefinder Technology Through the Years

Advancements in Rangefinder Technology Through the Years
My October 2019 Montana mule deer was a beauty, with a score over 180 inches. Quick rangefinding and angle compensation helped me make the 30-yard shot.

Just last October I watched a wide-racked mule deer bed on a near-vertical slope. I had been hunting this specific Montana buck for over two weeks, and almost everything that could go wrong had. As I glassed from 400 yards, I realized this was my best stalking opportunity so far.

A lone, dead pine was directly above the buck, and as I tiptoed the final 30 yards, I took several distance and angle measurements to rocks and foliage below.

A muley doe bolted from a dip below me, and the buck stood to gawk around beside a bush I’d already measured. The actual distance was 30 yards, but the 22-degree angle meant a 25-yard hold. I had already done the math in my head.

The Hoyt bow thumped, the Easton arrow flickered, and the Striker V2 broadhead smashed home. The buck catapulted down the hill and flipped upside-down. His antlers later scored over 180 record-book points.

I have the deepest respect for archers who shoot without sights. That’s how I started bowhunting, and I was reasonably accurate by instinct. But there is a reason “barebow” shooters always compete in a separate tournament category. As I found out many years ago after I affixed a multi-pin sight to my recurve bow, an aiming pin is always more accurate if you know the distance to your target.

In open country, animals tend to appear closer than they really are. In deep woods, critters seem farther away. Even with practice, it’s easy to blow distance by eye. Broken ground, ravines in between, or intervening bushes can all distort your judgment. So can animals smaller or larger than you’re accustomed to hunting.

For this reason, rangefinding devices appeared on the market more than 40 years ago. Some were simply a bow-attached array of wires, bars, or rings that were supposed to match a deer’s body depth at different distances. If your target deer’s theoretical 18-inch chest fit inside the widest gap, the animal was about 20 yards away. If it fit inside a smaller gap, it might be 30, 40, or 50 yards away.

These rough-estimating gadgets were just that — very rough. Deer vary in body depth, even within the same subspecies, and chest size tends to shrink on animals viewed from sharply above or below. And what could you do on a bowhunt for antelope, caribou, or elk? Deer-judging gaps were useless.

So-called “optical rangefinders” became popular in the 1970s and ‘80s. These were long, bulky devices with two widely separated viewing windows up front, a single eyepiece to the rear, and a rangefinding wheel marked with various yardages. You simply viewed the target, turned the wheel until double images merged into one, and read the distance.

This basic principle was vastly superior to eyeball-estimating or gap-ranging animals, but problems persisted. The farther apart the frontal viewing windows, the better the distance triangulation and geometric accuracy. Long units, like the Ranging LR-80, weighed more than a pound and measured nearly a foot in overall length. This made them cumbersome to carry and use. More compact units, like the Eagle Eye 50, gained popularity because they weighed less than six ounces and measured only five or six inches long. But these had closely separated viewing windows that made image merging and distance measuring touchy, and geometrically unreliable.

Perhaps the best optical rangefinder was the Ranging Eagle Eye 3X. This unit featured viewing windows barely eight inches apart, a weight under one pound, and a three-power eyepiece for more precise image acquisition. But this rangefinder shared one troublesome trait with all the others — it required a target with a clean vertical line like a tree, rock, or deer antler to work properly.

I was thrilled when the first compact laser rangefinders hit the market in the 1990s. An average unit, like the Bushnell Yardage Pro, was palm-sized and weighed only six or eight ounces. Operation was ridiculously easy. You simply punched a button and read the distance to the target through the viewfinder.

Most of the first laser rangefinders were reasonably accurate. Improvements were made in a few short years, including bright LED readouts in better units; “rain modes,” so laser beams could penetrate thin screens of precipitation or even grass; and “scan modes” for instant distance updates on moving targets.

But one shooting problem remained. How could you compensate for upward and downward angles? Like all projectiles, arrows hit higher than normal when shot at targets above or below.

The usual advice given by magazine writers, seminar speakers, and early TV hunters was simply to practice up and down shots to get a “feel” for how to aim. But with an infinite number of distance/angle shooting combinations in the woods, who could possibly control such shots with any precision?

Struggling with this dilemma from the time of optical rangefinders, I devised my own angle-aiming solution in the 1980s. I purchased a Finnish Suunto clinometer — a palm-sized and incredibly precise angle-measuring device used by timber cruisers to determine a tree’s height and board feet of lumber. This item let me determine the exact shooting angle in degrees. Through trial and error, I developed a simple mathematical formula that let me convert real distance and shooting angle into the distance I actually needed to aim.

This formula only works with my bow, arrow speed, and where I anchor the bowstring. I have used it so much that I can do the mental calculation in seconds.

A more practical option for general consumers is the so-called “arc” rangefinder. An internal computer and angle meter instantly compensate for upward/downward shooting angles by calculating the cosine (horizontal distance to the target). One of the first of this kind was my own signature Bushnell Bowhunter Rangefinder, introduced in the early 2000s.

Such devices are commonplace today, but you should be aware that they’re not a cure-all for angled shooting. Exact arrow speed and where you anchor the bowstring to your face can alter upward/downward arrow impact. Most archery setups hit higher than an arc rangefinder indicates. The slower the arrow, the more dramatic this discrepancy is.

I recently replaced my Swarovski laser rangefinder and Suunto clinometer with a rangefinding binocular. This particular 10X model from Leica has a bright LED readout, precise accuracy as close as 10 yards, and an electronic angle meter. And the one-hand operation is as simple as pressing two buttons. In the quick-moving situation described at the start of this column, I doubt I would have nailed that big mule deer if I’d had to manipulate a separate binocular, rangefinder, and angle meter.

You get what you pay for in hunting optics, so check out various rangefinders and buy the best you can afford. Preventing high or low hits is part of an ethical archer’s job, and nothing can help more than the right rangefinding device!

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