Sighting And Accuracy
A powerful air rifle shooting excellent pellets is totally ineffective on game unless the pellet can be placed in a lethal zone on the animal. Accuracy is absolutely necessary in a hunting rifle. It is often said that a rifle is no better than its sights. Rifles do not function in the same way as shotguns that rely on a large number of pellets or shot to provide multiple hits on the target. The single projectile fired from a rifle must be directed accurately to the target. Therefore, the hunter who uses an air rifle must have sighting equipment appropriate to the task. There are four types of sights that are in common use on hunting rifles.
For centuries, sights on rifles have consisted of two raised points on the barrel that could be aligned with the target. Those two points usually consist of some sort of notch in a blade to form the rear sight and a bead or post front sight that is viewed through the notch in the rear sight. This arrangement constitutes what is generally referred to as the “open” or “iron” sights that are mounted on the barrel. A couple of generations ago, almost all rifles (both firearms and air rifles) were produced with sights of this type. They are inexpensive and effective enough at reasonable ranges if the shooter has good vision. Moreover, they do not add much weight or size to the rifle, but it is a fact that it is impossible to focus simultaneously on three points at different distances from the eye. The rear sight, front sight, and the target can not all be seen sharply at the same time. The front sight on an air rifle generally has a shape that is one of the two types shown in Figure 5. The front sight is usually a square topped post or a post with a bead on top.
In most cases, the rear sight has either a square notch in the blade or a notch with a round bottom. If the front sight is a square topped post, the rear sight normally has a square notch, and a rounded opening is used if the front sight is a bead. The alignment of the front sight with the rear is shown in Figure 6.
When using open sights, it is necessary to place the front sight in the notch in the rear sight and then align the front sight on the target. This is known as the sight picture. However, there is still some choice as how the front sight should be aligned on the target. Two ways of aligning a post or bead front sight on the target are illustrated in Figure 7. In target shooting where the aiming point is uniform size and shape, it is customary to have the sights adjusted so that the bullseye rests on the top of the front sight. It is difficult to see the correct placement when a dark colored post or bead is being viewed against a black background. However, in hunting, the sights should be adjusted so the top of the post or bead is placed in the center of the target. A game animal does not have a regular shape and it may be located at different distances from the muzzle. Therefore, a sight picture like that shown in Figure 7 in which the top of the post or bead placed where the pellet is supposed to strike is a better arrangement.
If the rear sight is one in which the front sight is a post and the rear sight has a square notch, the situation is slightly different. Figure 8 shows the alignment of a rear sight with a square notch, a square topped front sight, and a round target to give two types of sight pictures. When targets of different sizes and shapes are encountered, the sight picture on the right is preferable.
It is necessary to adjust the sights on an air rifle so that the pellet strikes the target (the point of impact) at the intended location (the point of aim). This process is known as “sighting in” the rifle. In most cases, the front is rigidly attached to the barrel so it is the rear sight that must be moved. The rifle should be held on a steady rest such as sandbags on a shooting bench to remove the human error that results from shaking. Then, three shots are fired at the target using the sight picture chosen, and the center of the three-shot group located in relationship to the center of the target. Next, the rear sight is moved in the direction you want the point of impact to move on the target. For example, if the shots hit low and to the right, raise the rear sight and move it to the left. The rear sights on most airguns can be raised or lowered by moving a small ramp that has a series of notches. The sight is raised or lowered by sliding the ramp forward or backward to adjust the elevation. In other cases, the adjustment is made by turning a screw that moves the rear sight blade. The horizontal adjustment or windage is made by moving the rear sight blade laterally. This normally requires that a retaining screw that holds the rear sight in place must be loosened and the rear sight moved either left or right as needed. It is not possible to tell how much the point of impact is changed as the rear sight is moved because there are no calibrations so it is a matter of trial and error. Other types of rear sights have an adjustment screw that must be turned to move the sight. After the retaining screw is tightened or the adjustment screw is turned, another group of three shots should be fired and the position of the group noted. Another adjustment can be made if necessary to bring the point of aim to the point of impact. Regardless of how open sights are utilized, they represent a simple arrangement that is limited in how accurately they can be aligned on the target.
Shooting a rifle with open sights requires the shooter to try to focus his or her eye on the front and rear sights and the target simultaneously. Additionally, if one has less than perfect vision, it may be difficult to position the front sight in the rear sight notch in exactly the same way for each shot. Consequently, open sights are not conducive to fine accuracy. A major step in the direction of accuracy is provided by the aperture or peep sight. In this case, the shooter looks through a small hole or aperture past the front sight to align it on the target. The aperture is never in sharp focus because it is placed close to the shooter’s eye. There are several advantages of peep sights over the open variety. First, the peep sight is normally placed on the receiver relatively close to the shooter’s eye. That means there is a greater distance between the front and rear sights, which reduces the sighting error. Second, when using a peep sight, the shooter looks through the opening, not at it. The brightest spot is in the middle of the opening so the eye naturally seeks this point as the place through which to view the front sight and the target. The result is that alignment of the sights is much more accurate and precise than it is with open sights. Third, peep sights are produced with adjustment screws that move the aperture a small, reproducible amount with each “click” of adjustment. Consequently, it is possible to sight in the rifle more easily and accurately than is possible with open sights.
As in the case of open sights, there remains the question of how to position the front sight in the aperture and how to align it on the target. The two most common ways are shown in Figure 9.
In the drawing on the left, the six o’clock hold is illustrated in which the top of the front sight rests in what would be the “6” position on a clock. This is the classic arrangement when the paper targets are of uniform size and shape as in the case of target shooting. For some applications such as hunting, it is preferable to adjust the sight (as shown in Figure 9(b))so that the top of the post rests at the center of the bullseye or other type of target and the pellets strike at that point. In that way, the top of the post can be aligned on the animal where the pellet is supposed to hit. In either sighting arrangement, a peep sight makes possible fine accuracy as is demonstrated by the phenomenal scores established in target competition where only metallic sights are allowed. Sighting in a rifle with a peep sight is done exactly as described above for open sights.
If there is one aspect of shooting that has changed drastically it is the use of scopes on rifles. Today, even many new rifles are not equipped with open sights because it is recognized that they will be used with scopes attached. Because it so much easier to shoot accurately with a scope, this situation is true even for air rifles. On many models, the open sights are simply omitted, but the rifles are designed so that a scope can easily be attached. Many air rifles that are suitable for use in hunting are sold as combination with a scope. With air rifles, this usually means some bar or rail with grooves or notches is located on the receiver so that a scope mount can be attached.
For the vast majority of shooters, the most accurate aiming device is the telescopic sight or scope. Such an optical device removes the necessity of trying to keep multiple objects in focus simultaneously. A scope sight consists of a telescope of some magnification that contains an aiming device known as the reticule. As a result of the optical design of a scope sight, the reticule and the target appear to be at the same distance from the shooter’s eye so both are clearly in focus. It is necessary only to align the reticule on the target to establish the aim point.
Scopes are produced with several types of reticules, some of which are illustrated here in Figure 10.
Although the standard crosshair was formerly the most popular type of reticule, the fine lines can be hard to see against a background of tree limbs or in dim light. The dual thickness reticule has the advantage of the thick sections being visible in dim light but the thin lines at the intersection permit accurate aiming. As a result, the eye picks up the thick sections quickly and then the final positioning of the reticule on the target is done using the fine lines. The crosshair with a dot at the intersection also makes the reticule visible on the target in dim light. The Mil-Dot reticule offers the advantages of the crosshair reticule but with dots along the wires that can be used for range estimation. However, this should never encourage the hunter to simply try to “hit” the game. If the game is too far away to place the shot accurately, don’t shoot! Wounded game escaping to die slowly is not the way to convince anti-hunters that we are ethical in our sport. Although these are some of the most common types of reticules, there are many others that have been devised to circumvent some real or perceived difficulty. Any of the reticules will work well for most types of shooting.
Not only does a scope make it possible to sight in the rifle more easily, it enables the shooter to see the magnified target more clearly. There is a tendency to think that “if a little is good, more is better” when it comes to magnification. Magnifying the target is achieved only at the expense of having a smaller field of view and less depth of field where objects are in sharp focus. However, tests have shown that if a shooter can shoot groups of a certain size with a 4X scope, the group size does not shrink to half that size if a scope of 8X magnification is used. Although it is reduced somewhat, the aiming error is not cut in half by doubling the power of the scope. In fact, tests have shown that the sighting error when using a 4X scope is reduced by only about one-third when using a 24X scope. A good scope of 4X or 6X magnification will permit fine shooting. A variable power scope of about 3-9X magnification makes a good choice for all around shooting. There is a trend toward scopes of higher power and those of 4-12X are also popular. However, a hunter does not usually go through the process of turning a dial at the time game is sighted, and many scopes of variable power are left set on one magnification. It is still hard to beat a really good 4X or 6X scope for general shooting. Higher magnification makes the target look large and may tend to encourage hunters to take shots at longer, unreasonable distances.
Assuming that the scope has been properly mounted, sighting in the rifle is carried out in the same way was as described earlier. However, scopes have adjustment knobs with arrows on them to show the direction they should be turned to move the point of impact in the desired direction. Also, turning an adjustment knob moves the point of impact a specific amount at some distance for each “click” the knob is turned.. The most common amount for each click is ¼-inch at a distance of 100 yards in which case it would require four clicks to move the point of impact by one inch. Keep in mind that if a scope adjustment gives this amount of change at 100 yards, one click will move the point of impact only 1/8 inch at 50 yards, 1/16 inch at 25 yards, etc.
So what is the best type of sight? By itself, this question has no answer. It depends on the type of shooting you plan to do. If you are going to hunt small game and pests, accurate placement of the pellet on the target is extremely important. For most of us who do not have eyes like an eagle, that means a scope is required. In fact, although I enjoy shooting handy multi-pump rifles, they are not as easy to handle when a scope is attached. Given the ease of configuring a PCP with a scope, the convenience of being able to fire a large number of shots by loading only a pellet each time, and the high power of such rifles, I have just about ceased to hunt with anything else. For shooting at silhouettes of animals or for hunting small game or pests, a scope is the best aiming device.
Keep in mind that a scope on top of your airgun changes its center of gravity and adds weight and bulk. Neither open sights nor a peep sight adds much to the dimensions or weight of the rifle. Adding a scope or a fine peep sight may cost as much as the gun itself did originally. So, the type of sighting equipment used depends on the type of shooting you will do and the level of accuracy you wish to achieve. Whatever the type of sight chosen, sight in your rifle carefully with pellets that give good accuracy in your rifle.
Jim House began shooting with a single shot BB gun at a very early age. Now, seventy years later, he is an airgun enthusiast. After a 32-year career as a chemistry professor at Illinois State University, he has written extensively about shooting sports, which has resulted in the books American Air Rifles and CO2 Pistols and Rifles. His books also include The Gun Digest Book of 22 Rimfire and, with his wife Kathleen, Customize the Ruger 10/22. Jim is the Reloading Editor for Gun World magazine and a Contributing Editor for The Varmint Hunter Magazine, The Backwoodsman, Airgun Hobbyist, and The Illinois Shooter. Although a lot of his work is with firearms, he maintains a keen interest in airgunning while also serving as Adjunct Professor of Chemistry at Illinois Wesleyan University.