Targeted: Complete Guide Of How Laser Rangefinders Really Work

Modern laser rangefinders have changed the way we hunt. Unknown distances are no longer a thing. We can range, dial, and fire with effect that would have blown the minds of our grandfathers. However, relatively few hunters understand how laser rangefinders work (or why they sometimes don’t work). Or, for that matter, how to get the best out of one. Following is an inside look at rangefinders and the lasers devices they employ, as well as how to work one like a pro.

Laser Brain

Every laser rangefinder employs a laser-emitting diode and a receiver. The diode, usually classed as something like an eye-safe Class 1 EN/FDA laser, shoots the beam downrange; the laser reflects off of whatever object it encounters, and the receiver reads how long it took to go there and back. Since the laser signal travels at a consistent speed, that travel time can be used to calculate how far away the reflecting object is.

Naturally, the more powerful the laser is, the farther away it can travel and still have enough juice to bounce off an object and return. And of course, the more refined the laser emitting and receiving devices are, the more consistent the results will be. It goes without saying that premium laser rangefinders perform better, and cost more.

There’s another performance-enhancing aspect of lasers that many serious long-range hunters consider crucial: the shape of the laser beam. Unlike what you see simulated in the movies or projecting out of your laser pen, the laser beams projected by the best rangefinders are not round. Rather, they’re wide and relatively shallow, like a rectangle in cross-section. This minimizes the beam’s likelihood of bouncing off of multiple objects at various distances.

For example, the laser in Gunwerks’ cutting-edge Revic BR4 rangefinder has a divergence of 1.6 MRAD wide (about 55 inches wide at 1,000 yards) but only 0.2 MRAD tall (about 7 inches at 1,000 yards). As a result, premium rangefinders such as the BR4 are more precise than inexpensive rangefinders that project a large round or square laser beam.

Lesser rangefinders don’t typically list the divergence specs of their beams, because they’re often pretty big—which is unflattering. Big lasers bounce a lot more signals off a lot more various objects, making it much harder to achieve a clean, consistent measurement. And the farther the target, the worse the discrepancies. That’s not to say that a basic rangefinder won’t serve just fine for practical shooting distances. For the most part, you’re fine out to 400 or 500 yards with inexpensive models. Past that, you’re going to want more quality in order to achieve the precise distance measurements long-range hunters require.

Laser Use

This is not an instruction manual that discusses modes, and features, and cycle buttons, or on-board sensors and calculators. This is an overview on how to make your laser device—whatever it is—read distance as consistently as possible.

Two common elements that cripple laser rangefinders are user instability (shake), and distance. The first can be overcome with good technique. The second is harder—if your rangefinder can’t shoot that far, you’re out of luck until you buy a more powerful device.

So, what’s that good technique? For starters, you need to get steady. If you’re shaking and the laser reticle inside your rangefinder is dancing all around your target, you’ll never achieve a consistent range measurement. You may find your rangefinder can’t achieve a reading at all. Brace your elbows or the rangefinder against a sturdy object. Heave a deep breath to oxygenate the quiver out of your muscles, glue the laser reticle on the deer or target or rock or tree you’re trying to range, and gently press the send button. Then follow through, holding still as Lot’s wife until the device displays a result.

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Lasers reflect differently off of various objects. Deer and elk are actually pretty lousy things to bounce a space-age light beam off of. Trees are better, and rocks are better. If you can’t get a reading off a deer, you may have to find a nearby object that’s more reflective and zap it instead. If you’ve got time, range a couple of other handy objects around your target, just to confirm you’re in the ballpark. Then re-laze your target. Assuming the result is the same (or very nearly), transition to your rifle.

If you’re trying to range an ELR target (Extreme Long Range), you may have to mount your laser rangefinder on a tripod. And you’ll need a premium device; entry-level gear won’t make the cut.

Lazy Lasers

What about those times when your laser just won’t laze? There are a few things that flat-out kill a rangefinder’s capability.

One of the worst is fog. Snow and rain also pose challenges. Anything flying through the air between you and your target will reflect laser light back to the receiver, and your rangefinder will cough out a result on something that is nothing at all. Fog, in my experience, is the worst.

What can you do to overcome it? Wait for the sunshine to burn it off, or for the snow or rain squall to blow through. Meanwhile, if your rangefinder offers various modes designed to deal with obstructions, work through them and try each. Sometimes, you’ll get lucky and the device will perform.

Another—and worse—problem can occur if your rangefinder gets dropped hard, and the laser-emitting diode inside shifts during the impact. If it shifts, it’s no longer pointing where the reticle in your viewfinder says it is. You’ll get measurements, but they’ll be wrong.

The best way to test your rangefinder if it takes an impact is to range side-by-side with a buddy, checking the results against your pal’s results. If you’re out solo, find something like a road sign and range it. If your laser isn’t centered with your reticle, it’ll likely shoot past the sign and range something way beyond. Zap the sign center, then the edge of the sign on each side and top and bottom. Finally, range past the sign, aiming out a few inches from the edges. It’ll become apparent if your rangefinder is shooting straight.

If it’s off, or biased strongly one way or another, you may have to send it in for re-calibration.

A simpler issue is dust and detritus on the lenses. If there’s crud on the laser-emitting diode, it will cause refraction and degradation to the beam. If there’s a layer of dust on the lens covering the receiver, it will cripple the devices’ ability to read incoming signals. These issues, of course, are easy to resolve—keep your rangefinder clean.

Buy quality, aim steadily, and keep your rangefinder clean. It’s a pretty simple manual of arms for such a complex device.