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Third-Axis Adjustment

Third-Axis Adjustment

Bottom line: If you expect long uphill and downhill shots, you need a sight with third-axis adjustment.

I touched on third-axis sight adjustment in a previous column, but this subject is important enough that it warrants more consideration.

Third-axis sight adjustments can have a profound effect on the outcome of western hunts where the shot distance may be long and the shot angle severe.

Third-axis sight adjustments can have a profound effect on the outcome of western hunts where the shot distance may be long and the shot angle severe. In tree stand settings, typically, the shot angle decreases as the shot distance increases--reducing the negative aspects of poor third-axis adjustment. However, even if you only shoot whitetails from a tree stand, you will see a small, but noticeable, improvement in accuracy by taking the following recommendations to heart. And if you are a western hunter hunting in steep country, these steps are mandatory.


What Is Third-Axis?
The third-axis of the sight is the rotational axis that the sight level moves on as the sight body angles either toward you or away from you at full draw. If you are holding the bow at full draw in front of you, the level should be exactly perpendicular to your line of sight. The level should not angle toward you or away from you. If it does, this slight angle will throw your bubble level off when you shoot uphill and downhill.


Assume that your sight body and therefore your level are grossly angled toward you. The end of the sight head (the side with the pin guard) is closer to your eye than the base of the sight body (where you adjust the sight pins). This is really no big deal if all your shots are on level ground because your bubble level will continue to read true.

However, if you aim upward or downward, the bubble level will deceive you. For example, if you aim sharply downward, the end of the sight body is still angled toward your eyes. Only now, your eye is above the sight since you are aiming downward. That means that the sight body is actually angled upward slightly and the bubble within your level will move toward you. Of course, being a conscientious archery hunter you are certain that you must now tip the bow slightly to your left (for a right-handed archer) in order to center the bubble again. As a result, you will shoot to the left. Now if the sight head is turned away from you, the opposite will occur and you will shoot to the right.


As you can imagine, when you shoot uphill you will see the opposite effect. If the sight body is angled in toward you, the bubble will move to your right and you will tip the bow to the right to bring it back to center, causing a miss to the right. If it is angled out away from you, you will tend to shoot to the left.


As you can see, this has the potential to cause very serious left or right misses. The farther the shot and the steeper the slope, the farther you'll miss.

Setting Your Third-Axis
Unless you get really lucky and the level in your sight happens to be perfectly perpendicular to your line of sight at full draw, you will need a sight that permits third-axis adjustment. Only a small number of sights on the market permit this degree of adjustability. If a sight offers this adjustment it usually advertises it on the packaging or on the product's web site. If you are serious about accuracy in western settings, you will need to buy one of these sights.

The adjustment takes place either in the extension bar out near the sight head or at the level itself. Typically, you adjust a couple of setscrews to put the sight in its new position.

There is no systematic way to set the third-axis. Some archers use a sight jig designed for this purpose. Another way to adjust the third-axis is to place the bow in a shooting machine that holds it at full draw.

Unfortunately neither of these methods incorporates the biggest variable of all: You. I don't believe you can properly adjust the third-axis in the shop; you have to do it in the field. You must make the actual adjustment at full draw because the way you hold the bow and the torque applied by the harnesses to the cable guard turns the bow slightly.

You can demonstrate this torque easily by attaching a long stabilizer to the bow. The stabilizer lines up with the arrow before it is drawn, however, at full draw the stabilizer points well to the right of the arrow (for a right-handed shooter). The bow's sight does the same thing as the stabilizer. So, if you want your third-axis adjustment to be practical in the field, you must adjust it in the field. I suggest you find the steepest, longest slope around and shoot both uphill and downhill. Adjust your third-axis until you hit neither left nor right.

Remember, if you are shooting to the left on downhill shots, you need to turn the level (sight body) away from you and if you are shooting to the left on uphill shots the opposite is true. Left-handed shooters should simply reverse all these recommendations.

Bottom line: If you expect long uphill and downhill shots, you need a sight with third-axis adjustment.

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