The object here is to not assume that everyone knows how to sight in their rifle. There are many new hunters and shooters every day. When we go to the rifle range, we all want to be able to at least hit the paper target.  Before you do this you should understand how a scope functions.

Know Your Scope
Riflescopes have become far more sophisticated over the years, but the four most basic parts have remained the same. Working from front to back they are:

  1. The objective lens (or front lens) is critical to a superior sight picture.
  2. The internal erector lenses which right the image.
  3. The reticle, often referred to as the crosshair, provides the aiming point. 
  4. The ocular lens (or eyepiece lens) works with the other lenses to magnify the image, provide correct eye relief, and make diopter corrections.

How Scopes Work.
As light passes through and beyond the objective lens, the resulting upside down image is sent to the internal lenses. Known as erector lenses, these internal lenses return the image to a right-side-up position. Finally, the ocular lens makes a final enlargement of that image and sends it on to your eye.

How to Install the Scope
(Please read the entire handbook that comes with your scope before mounting your scope.)

Caution: Make sure your gun is unloaded before mounting your scope!

The Lower the Scope, the Better.
A scope mounted close to the rifle ensures proper cheek weld on the stock for a stable firing position and allows for rapid target acquisition.  Use the lowest possible ring height. No specific clearance is required, but the scope must clear the bolt handle, hammer (on lever actions and handguns), sights, and barrel.

When installed, be sure that your scope does not interfere with firearm operation and does not contact anything except the mount rings. 

Installing the Base, Rings, and Scope.
Please refer to the instructions included with the base and rings for their proper installation on the firearm.

Establishing Eye Relief on Rifles and Shotguns.

Because of the safety considerations associated with proper eye relief, it is recommended that you mount your scope as far forward as possible. Beyond that, follow these steps:

  1. With the scope as far forward in the mounts as possible, hold the rifle in your normal shooting position. (Variable power scopes should be set at the highest magnification for this process.)
  2. Slowly move the scope to the rear just until you can see a full field-of-view.
  3. Position your scope here for maximum eye relief.
  4. Proceed to COMPLETING THE INSTALLATION.

To confirm that your scope is mounted in the best possible position, try assuming various positions: kneeling, seated, prone, and aiming both uphill and downhill. Remember that aiming uphill typically reduces eye relief.

If a scope is mounted too far to the rear, the eyepiece can injure the shooter’s brow. Shooting at an uphill angle also increases this hazard because it shortens the distance between the brow and the rear of the scope.  Therefore, when mounting your scope, position it as far forward in the mounts as possible to take full advantage of the scopes eye relief.

 

Establishing Eye Relief on Handgun Scopes.
Since handguns are typically fired from an arms-extended position, eye relief is less of a safety issue than with riflescopes. However, it’s still important to get the eye relief right for you.

1. Holding the handgun in your normal shooting stance, position the scope in the rings to achieve a full field-of-view.
2. Proceed to COMPLETING THE INSTALLATION.

The eye relief of handgun scopes is more forgiving than that of rifle scopes. Nevertheless, it is important that the eye relief is compatible with your shooting style.

Unlike riflescopes, adjustments to the eyepiece in handgun scopes affect the eye relief as well as the reticle focus. Turning the eyepiece clockwise increases eye relief and turning it counterclockwise decreases it.   

Completing the Installation.

  1. Without disturbing the optimal eye relief position, rotate the scope until the elevation adjustment dial is at the top of the scope.
  2. From a firing position, check to be sure that the vertical hair of the reticle aligns with the vertical axis of the firearm. Misalignment will not affect accuracy at moderate distances but it can diminish long range accuracy.
  3. When you are satisfied, tighten the ring screws evenly and securely.  

Focusing the reticle.

Secure the scope and firearm in a firm rest. Point the scope at a light colored background object. With the scope approximately four inches from your eye the reticle should appear sharp and crisp; if it does not, it is necessary to adjust the focus by means of the eyepiece.

If your  scope is one  with an eyepiece that has a lock ring, follow these simple steps:

  1. Grasp the eyepiece with your hand and back it away from the lock ring. Once the lock ring is free from the eyepiece, turn it clockwise away from the eyepiece to keep it out of the way during the adjustment.
  2. If you tend to hold things away from yourself to see them clearly (you are farsighted) turn the eyepiece counterclockwise by three or four turns. If you hold things close to yourself to see them clearly (you are nearsighted) turn the eyepiece clockwise by three or four turns.
  3. Looking through the scope when pointed at the sky, take a few quick glances at the reticle. The focus of the reticle should be noticeably different from when you started. Continue this process until the reticle appears clear and sharp.
  4. When you are satisfied with the image of the reticle, turn the lock ring so that it rests firmly against the eyepiece.

If your scope is one  with a fast-focus eyepiece, follow these simple steps:

  1. All adjustment is made with the eyepiece.
  2.  Look through the scope with quick glances while focusing the reticle image. If you tend to hold things away from yourself to see them clearly (far-sighted) turn the eyepiece ring counterclockwise until the reticle is clear and sharp. If you hold them close to yourself to see them clearly (near-sighted) turn the eyepiece ring clockwise until the reticle is sharp and clear.

If your eyesight changes, readjust the eyepiece. As we age, eyesight normally changes. You may want to check the sharpness of the reticle on your scope every few years to ensure it is still adjusted correctly for your eye.


The primary function of a scope is to aim the firearm. Never use the scope as a substitute for binoculars. Never watch another person through the scope.

How to Sight In
Using a Bore-Sighting Collimator.
To save time and ammunition, start out in your shop or gun room with a bore-sighting collimator (a spud and an optical assembly) to “get on the paper.” Remember that adjustments made during bore-sighting will appear to move in the opposite direction than that indicated by the adjustment dial.

  1. Assemble the collimator with the correct spud and insert it into the barrel. 
  2. Look through the scope. Note that the collimator displays a crosshair that is at 45º to the scope’s reticle. The center of the scope reticle is normally some distance away from the center of the boresight reticle. This shows the scope’s line of sight relative to the axis of the bore.
  3. Begin with the windage adjustment. (Remember, when possible, it is better to make the initial windage adjustments to the mount base before using the scope’s windage adjustment.) Turn the windage adjustment until the vertical crosshair of the scope covers the center of the collimator crosshair. 
  4. Adjust the elevation until the horizontal crosshair of the scope covers the center of the collimator crosshair. With that, the scope should align with the axis of the bore. 
  5. Remove the collimator spud from the barrel.

Bore-sighting alone is not sufficient to sight-in a scope. You must make final adjustments by shooting the firearm using the same ammunition you use in the field.  

Traditional Bore-Sighting (Bolt Actions)
Preliminary sighting-in can also be accomplished by bore-sighting at the firing range using a target from 20 to 50 yards away.

  1. Position the firearm on the bench, using sandbags to steady the firearm.
  2. Remove the bolt from the firearm.
  3. Looking through the bore itself, move the firearm to center the bull’s eye of the target inside the barrel.
  4. Hold the rifle steady. With the bull’s eye centered when viewed through the bore, make windage and elevation adjustments to the scope until the very center of the reticle is aligned with the bull’s eye of the target.

Bore-Sighting Lever Actions
An inexpensive device with a small mirror, which inserts into the chamber or rests on the magazine follower to allow sighting down the barrel, is necessary for bore-sighting lever action rifles. 

The Final Step: Three-Shot Groups
Whichever bore-sighting method you’ve used, the next steps are the same on the firing range. To ensure reliable results, always fire from a rested position when performing these steps.

  1. Fire a shot or two.
  2. If you are several inches off center, make an appropriate amount of adjustment to move the reticle to the center of the target.
  3. Carefully fire a three-shot group. 
  4. Use the center of that group as a reference point for the final adjustments to windage and elevation.

On the sample target, the center of the group is two inches low and three inches right. Assuming you’re sighting-in at 100 yards, you should make a 2-MOA adjustment up, and a 3-MOA adjustment left. Your next three-shot group should be very close to the center of the target. To learn about making final adjustments, proceed to the upcoming section on windage and elevation adjustments.  

Making Precise Windage and Elevation Adjustments
The style of elevation and windage adjustments on  scopes varies with specific models. If you are unsure of the value of your scope’s adjustment increments, follow these steps.

Determining the value of adjustment increments:

  1. Count the number of hash marks—from zero to and including that of the first number—on the dial.
  2.  Divide the first number on the dial by the number of hash marks counted. For example, divide 1 (the first number on the dial to which you counted) by 4 (the number of hash marks counted) to get .25 or 1/4.

The resulting number is the value of each increment of adjustment in MOA. This method will work with almost any  adjustment dial. One MOA moves the point-of-impact at 100 yards by one inch (at 100 meters, it moves 29mm).

The windage adjustment has arrows pointing at an “L” for left or an “R” for right. The elevation adjustment has arrows pointing at a “U” for up or at a “D” for down. All of these symbols refer to the direction that the point-of-impact of the bullet is moved.  

What You Should Know About Variable Power Scopes
Variable power scopes allow you to select from a range of magnifications to suit your particular rifle, cartridge, and shooting needs.

All variable power scopes have a power selector ring in front of the eyepiece assembly. Turn the ring to align the number indicating the desired magnification with the dot on the body of the scope. 

Understanding Parallax
Parallax is the apparent movement of the target relative to the reticle when you move your eye away from the center point of the eyepiece. It occurs when the target does not fall on the same optical plane as the reticle.

Maximum parallax occurs when your eye is at the very edge of the exit pupil.

At short distances, the parallax effect does not affect accuracy.  It is also good to remember that, as long as you are sighting straight through the middle of the scope, or close to it, parallax will have virtually no effect on accuracy in a hunting situation. 

Scope Maintenance
Lenses
Scope lenses are coated to reduce light reflections and light scattering thus increasing light transmission through the scope. They should be cleaned as carefully as you would a camera lens.   Use a standard lens brush to remove dust and then pure alcohol, high-grade glass cleaner, or pure water on a cotton swab to clean the lens.

Windage / Elevation Adjustments
These adjustments are almost always permanently lubricated. There is no need to lubricate them. Keep the turret caps on, except when adjusting, to keep out dust and dirt.

Seals
Most scopes are sealed from within by several methods, including O-rings. All seals are permanent and require no maintenance.   

Scope Exterior
No maintenance of any kind is required; simply wipe off any dirt or fingerprints that accumulate with a clean, dry cloth. 

Trouble Shooting Tips
Before you ship a scope back to the manufacturer for service or repair, please check the following items to make sure that the problem is really with the scope and not the rifle or mount system.

  1. Check the mount. Make sure the scope is mounted securely to the rifle. Try, with bare hands only, to twist the scope in the rings or see if anything moves when you jiggle it. If there is any movement, retighten the mounting system according to mounting instructions.
  2. Make sure the action of your rifle is properly bedded in the stock, and that all receiver screws are tight and have been tightened in the sequence recommended by the manufacturer. A loosely fitted stock can cause changes to the point-of-impact.
  3. When test firing a rifle to check the point-of-impact relative to windage and elevation adjustments, be sure to fire from a solid bench with sandbags supporting the forearm and buttstock.
  4. Be sure to use factory-loaded ammunition of the same bullet type, weight, and preferably, lot number. If one type of ammunition does not shoot well, try another brand or bullet weight.
  5. Be certain that both the barrel and chamber are clean. Heavy factory grease on a new rifle and copper fouling on an older one can diminish the accuracy of the firearm.