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Sighting in, or zeroing, is the act of calibrating the sighting system by adjusting the windage and elevation so the point of aim and the point of impact (bullet strike on the target) coincide at a certain distance.
A rifle scope is a telescopic sighting system that provides variable or fixed magnification. Rifle scopes use a reference point called a reticle that you place on the target. This is your aiming marker.
Rifle scopes usually have two dials — one for adjusting windage and another for elevation. In addition, a variable-power rifle scope has a magnification selector. Some models feature a throw lever — a miniature handle that you can use to adjust the magnification rapidly.
How to Sight In a Rifle Scope
When you’re learning how to sight in a rifle scope, it’s important to remember that the zero is for a specific range. If your rifle is sighted in for 100 yards, its point of impact will not be the same at 300. That’s due to the effects of gravity and drag. Drag, or air resistance, causes the bullet to decelerate. The rate at which the bullet loses velocity depends on several factors, such as the ballistic coefficient of the bullet.
If your rifle scope is not properly sighted in or zeroed, you can’t expect your shots to hit where you’re aiming, rendering accurate shooting impossible.
You may consider bore-sighting your rifle, although whether you consider that to be either necessary or sufficient is for you to decide. Bore sighting is simply looking through the barrel at the target and aligning the bore with the scope. This is relatively easy with rifles that you can remove the bolt from the rear.
You’ll also need a sturdy bench or other flat, stable surface on which to set up your rifle. Lay your rifle on two rests: front and rear.
A rifle scope has, at a minimum, dials for adjusting the windage and elevation. Windage determines the strike of the bullet on the horizontal plane — from right to left. Elevation determines the strike of the bullet on the vertical plane — up and down.
Some rifle scopes also have a separate dial for adjusting parallax. If you have a parallax-adjustment dial, use that first to focus the rifle scope on the target you intend to shoot.
Following parallax adjustment, focus the reticle on the target at the desired magnification. To test the scope for parallax, shift your head from side to side and observe the target and the reticle through the scope. The reticle shouldn’t wander during this test.
Set up a paper target, preferably one that uses 1-MOA squares. Fire a 3–5-shot group at a point on the target. Fire these shots slowly while practicing the fundamentals of marksmanship. Ideally, dry-fire the rifle a few times before loading it with live ammunition to see how your trigger control feels.
Determine the range at which you intend to fire and, thus, zero your rifle. You may decide that you should shoot at a 25-yard target initially to ensure that your shots land on paper.
Determine on the target the distance; in minutes of angle, your shot group is from the point of aim (where you were placing your scope’s reticle). If, for example, your shot group is 4 MOA above the point of aim and 4 MOA to the left, you need to adjust the rifle scope accordingly.
In this example, your adjustment will be four MOA down and four MOA to the right. Removable caps typically protect the windage and adjustment dials or turrets on a rifle scope. Remove these caps and adjust the dials either clockwise or counterclockwise, depending on what the dials indicate and what corrections are necessary.
Windage and elevation dials often shift point of impact in increments of one-quarter or one-half MOA. If the windage dial moves the strike of the bullet one-quarter MOA every click, you’d need to turn it 16 clicks to the right to shift the point of impact four inches to the right at 100 yards (4 MOA).
Once you’ve made the necessary adjustments, return the turret caps to protect the dials.
Fire another string of 3–5 shots at the target and evaluate the point of impact. Repeat this exercise as frequently as necessary to achieve the desired effect.
The ammunition you choose to sight in your rifle should be consistent with what you intend to shoot when hunting, competing, or for recreation. Don’t attempt to zero your rifle using low-quality or high-MOA military surplus ammunition if you’ll be using match-grade target ammunition.
Your choice of ammunition has a direct influence on the point of impact. For example, if you zero your 7.62mm rifle using 147-grain M80 ball ammunition, then shoot 175-grain M118LR, you shouldn’t be surprised if your shot groups print differently.
It’s essential that you place your cheek in the same position on the comb — the top of the stock — every time. This is called the stock weld. A consistent stock weld equates to consistent eye relief, which will affect your perception of the scope reticle. Eye relief is the distance between the ocular lens and the dominant eye. Furthermore, sufficient eye relief is necessary to minimize the risk of scope bite.
Accuracy vs. Precision
Although the terms “accuracy” and “precision” are often used interchangeably, they have distinct meanings.
Put simply: accuracy refers to how close your shots are to the point of aim. This is what you’re trying to achieve when you sight in your rifle. Precision, however, refers to how closely spaced your shots are to each other — the tightness of your groups.
A shot group can be precise but inaccurate. Once you’ve established the accuracy of your group by properly sighting in your rifle, you should determine the extent to which you need your shots to be precise.
How accurately do you expect to shoot this rifle, and under what circumstances? A rifle for hunting deer at 100–200 yards doesn’t have to be as precise as a benchrest rifle or a varmint rifle. Your target area is relatively large.
If you want to make field-expedient adjustments to windage or elevation to compensate for environmental conditions without compromising your zero, you can change the reference points on the dials, so your adjustments appear as zero.
To perform this action, simply remove the turret caps and unscrew the dials using the edge of a coin. Re-align the markers on the dial so that the “0” aligns with the front of the turret.
As part of learning how to sight in a rifle, you should ensure that you practice the fundamentals of marksmanship, including follow through, consistently. These consist of position, sight picture, trigger control, breath control, and follow through.
Sighting in your rifle scope is necessary to gain the most from your use of this optical sighting system. However, sighting in your rifle is only the first step. If you can’t hit what you’re aiming at, the rifle scope is useless. This requires a solid grasp of the fundamentals of marksmanship.