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As I sit here, drinking coffee at my kitchen table, I notice a gray squirrel flicking its tail in the crook of a tree in my backyard, about 30 yards away. The window screen I’m looking through across the room has a fly on it.

It is superimposed in line so exactly over the tiny vital zone of the tree rat that I could imagine it as a riflescope reticle mounted over a gun and could squeeze the trigger for a perfect kill shot. My focus is on the insect, and the rodent is blurry.

However, if I move my head any amount at all, the fly no longer stays in the right place; instead; it moves all around and over the squirrel, varying by the amount I move my head.

This, then, is “parallax”—when the target (the squirrel) is on a different plane (distance) than my reticle (the fly).

This Bushnell Elite 3200 Tactical 5-15x40 would not be appropriate on this Beeman R-1 air rifle without a 10-meter parallax adjustment.

This Bushnell Elite 3200 Tactical 5-15×40 would not be appropriate on this Beeman R-1 air rifle without a 10-meter parallax adjustment.

THE “GIANT” WHEEL

Now, let’s imagine your sight picture of the squirrel and fly is exactly the same as previously described, but you’re in a giant tube many feet in diameter. On the side of the tube there is a giant wheel, and when it is turned, the squirrel gets closer or farther away and less or more in focus, depending on which way you move the wheel.

If you move the wheel so the squirrel (target) is very close to the fly (reticle), no matter where you move your head when you are staring at the animal, the fly does not move away from the vital zone of the squirrel.

The giant wheel is your riflescope’s parallax adjustment turret. It adjusts the furry target to a close distance to the fly. As a result, it also puts the rodent in focus and eliminates the possibility of the reticle moving away from your exact intended point of impact, even though your head position has changed. When your target is close to the same distance as your reticle, parallax is removed, and your focus is sharp on both the reticle and the target.

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The adjustment wheel might be on the side of the scope (side focus) or in the front, surrounding the objective lens (adjustable objective). On the side is much more convenient to the shooter, because he doesn’t have to move his head from his cheek weld. However, the adjustment wheel on the front objective is much larger in diameter and might be easier to adjust in micro-increments. These adjustment wheels are often marked in distances—which might or might not be true readings but can be taken as an estimate.

PARALLAX ADJUSTMENT

Parallax can also be described as “the apparent movement of the reticle on your target when moving your head away from exact center of the riflescope.”

Does that mean that if you can keep your eye directly centered in the riflescope, parallax error will not be noticeable? Yes. That’s why a solid and consistent cheek weld is so important.

Parallax adjustment is especially crucial for precision shooting, such as 10-meter air gun shooting or benchrest, because scores and groups are often measured to hundredths of an inch. Every tiny bit matters. But for most shooters (hunters, in particular) who won’t shoot much farther than several hundred yards, it doesn’t matter too much, so don’t get overly concerned.

PARALLAX AND SCOPES

My first quality hunting scope was an old Leupold Vari-X III 3.510×40 with an adjustable objective. I generally kept it set at 200 yards and killed over a dozen various deer and speed goats up to 400 yards without troubling over the adjustments too much. (When moving your head around, parallax error is most apparent at close distances, rather than far.)

This is the Leupold VX-3 4.5-14x40 that started the experiment. “Look, ma—no parallax knob!”

This is the Leupold VX-3 4.5-14×40 that started the experiment. “Look, ma—no parallax knob!”

Preparing for an antelope hunt years ago, I wanted to use a Leupold VX 3 4.5-14×40 scope on my bicentennial Ruger 77, which had been rechambered for the superb .270 Weatherby cartridge. But I was concerned I might have a parallax issue with a non-parallax-adjustable 14x scope at long range. At least that’s what I was told by other shooters, and it was often in print.

I’m more of a minimalist; the fewer the parts and things I have on my equipment, the happier I am. A parallax dial is just one more thing to worry about. Some people are so concerned about adjusting their equipment and the “stuff” attached to their guns that they forget what their job is at the range or in the field: that is, to use proper form, cheek weld, breathing, trigger control and sight picture so they can take a well-aimed shot. And shoot quickly. How many missed opportunities for shots I’ve seen because people were futzing with their focus, magnification, bipod or some other unnecessary interruption! Animals don’t often wait or offer do-overs.

I secured a variety of scopes on tripods and taped a 1-inch grid sight-in target on the rear window of my Jeep. A friend carrying a Motorola radio drove the Jeep to different distances and stopped where I said, using a laser rangefinder to confirm yardages.

I centered the reticle on the bullseye and moved my head off center in all directions. This allowed me to count how many inches the reticle moved off center. It’s a pretty crude test, and there’s not room here to print all my conclusions, but here were some results that I found interesting.

With the Leupold VX-3 4.5-14×40 scope (parallax set at Leupold for 150 yards) turned up to 14x, the movement of my head from side to side until the picture blacked out resulted in the following approximate rounded-off number of inches that the reticle moved off center:

  • 100 YARDS: Zero movement
  • 150 YARDS: Zero movement
  • 200 YARDS: Less than 1 inch
  • 300 YARDS: 1 inch
  • 400 YARDS: Less than 2 inches
  • 500 YARDS: About 2 inches
  • 600 YARDS: Fewer than 3 inches

Again, these numbers are approximate. What has to be realized here is that to induce this maximum amount of parallax error, I had to move my head until I lost the sight picture because my head was so far off center. And you would never shoot a scoped gun like this! Even being anywhere around the center of the scope would keep your shots within a couple of inches from your point of aim.

PARALLAX PRESCRIPTION

Parallax correction is required for ultra-close shooting, particularly with high magnification, such as a target air gun scope. Even at 25 yards with a lower-powered 3-9 scope at 9x, you might need to adjust parallax in order to achieve a sharp picture.

Long-range precision scopes benefit from parallax adjustments also, because you need everything stacked in your favor for hits at 1,000 yards and farther. But for 90 percent of shooters and hunters using magnifications up to about 14x, parallax is not something to cloud your brain with.

SIG clearly marks parallax yardages on its new Tango 6 5-30×56 scope, shown here in the Kinetic Development Group QR modular SIDS-141 34mm mount. As of this writing, a custom elevation turret with your ballistic information is orderable with all Tango riflescopes, price included.

Adjustable objective scopes can often be adjusted in finer detail than side focus models.

LEUPOLD CDS

The Leupold Custom Dial System (CDS) is one of the simplest ways to shoot at distance. These custom dials are available from the Leupold Custom Shop and replace the elevation turret on many of that company’s scopes. They can be engraved with the ballistic information of any conceivable factory cartridge or handload, as well as for any atmospheric conditions.

Use your rangefinder to determine distance, dial the yardage, and hold right on. It’s one of the first and best— and still my favorite.

The vital zones of large animals offer such large targets that the maximum parallax error possible will not result in a missed shot. And if you keep your head centered through your scope with the aid of a solid cheek weld, most parallax issues are moot.

There’s enough data to write volumes about the subject, but if your shooting and hunting are pretty mainstream, and your head is dizzy from countless articles and information about the subject, prescribe yourself a cleansing parallaxative and just know that the gun and scope will do their jobs … if you do yours.

 

LEUPOLD CDS
The Leupold Custom Dial System (CDS) is one of the simplest ways to shoot at distance. These custom dials are available from the Leupold Custom Shop and replace the elevation turret on many of that company’s scopes. They can be engraved with the ballistic information of any conceivable factory cartridge or handload, as well as for any atmospheric conditions.

Use your rangefinder to determine distance, dial the yardage, and hold right on. It’s one of the first and best— and still my favorite.

The CDS’s MSRP is $59.99, but VX-3 CDS models come with a coupon redeemable for a free dial.

CONTACT INFORMATION

LEUPOLD OPTICS

1-800-LEUPOLD

www.Leupold.com

 

Editor’s note: A version of this article first appeared in the July 2017 print issue of Gun World Magazine.