Scope basics: Part 1
by Tom Gaylord, a.k.a. B.B. Pelletier
This article was originally written for the upcoming Pyramyd Air catalog. But there were so many new rifles and pistols that we didn’t have room for this. I felt it was important enough to get it out, so I’m publishing it on the blog.
You’d like to have a scope; but when you check into the subject, it gets very confusing, very fast. In this 2-part blog, we’ll explore the basics of scopes.
A telescopic sight, or scope, is a type of sight that magnifies the target, usually making aiming easier. It may have a fixed amount of magnification or the magnification may vary within a range, allowing the shooter to select what he wants.
Inside the scope are lines called reticles. One runs up and down and the other runs side to side. They intersect in the center of the field of view. They are the aim point that’s put on the spot where you want the pellet to go. They adjust in both directions, but you never see them move. They are held inside a tube inside the scope; and when they’re adjusted, the entire tube moves so they always appear centered.
If your rifle is sighted-in, the pellet should land fairly close to where the intersection of the reticles was when it fired. How close it lands depends on several things—how accurate the rifle is, how well it was held when it fired, how good a pellet you use, the weather conditions (especially the wind) and so on.
The rifle is always moving!
The first thing that surprises someone who looks through a scope for the first time is that the rifle is always moving. In the movies, the camera sometimes looks through scopes that never move; but in real life, they’re never still. The rifle is also moving when you sight with open sights; but since the target isn’t magnified, you cannot see the movement.
Just because there’s a scope on your rifle doesn’t mean it will be more accurate. You have to find ways to slow the movement and to eliminate or minimize it as much as possible. Once you learn to do this and to follow through after every shot, you’ll be rewarded with better groups and more accurate shots.
More magnification may not help
You would think that because a scope magnifies the target it automatically makes it easier to see and hit. Sometimes it does, but other times it does the opposite. When the magnification is too great and the target area is dark, you may not be able to find the target in the scope. When you hunt in the deep woods, for instance, a 4x scope will do a lot better than a 16x scope. You may be able to see the veins on each leaf through the 16x scope, but which leaf are you looking at?
Greater magnification also can make the image seen through the scope darker, and it may even appear as though it’s in fog. On every scope that has adjustable power, the amount of light that gets through the scope decreases as the power increases. This effect is offset by superior quality lenses and by special lens coatings, but the budget brand scopes don’t have these things.
Magnification — use what you need
Why do airgunners need so much magnification? Well, most of them don’t need it, but one group does. The field target shooter uses his scope to help determine the range to the target, so he can know where his pellet will be in its trajectory when it arrives on target. The difference of a yard or two can make the difference between a hit or a miss.
A field target shooter wants to see the smallest object he can possibly see at the farthest distance on the course, which is 55 yards. He’d like to be able to see a blade of grass so clearly at 55 yards that when he adjusts the parallax he can see the image come into sharp focus. If that blade of grass is standing next to the target he wants to shoot, he’s just determined the range to the target.
It takes a lot of power to see a blade of grass clearly at 55 yards in a dark forest setting. So, field target shooters use scopes of 32x, 40x and even 60x to resolve things this small. These scopes aren’t too useful for most shooting; but for the rangefinding task, they excel.
Most airgunners will do very well with 9x, 12x and even 16x. Scopes of that power will be smaller and lighter, and that translates to less fatigue while hunting. A squirrel hunter in the deep woods can get by with even less power. Maybe 6x is all he needs. Benchrest target shooters, on the other hand, have a stable platform and can spend some time finding the target in the limited field of view that a powerful scope gives. For them. the most important thing is being able to bisect the target as precisely as possible, so every shot is aimed at the same place. Understanding what magnification you need and matching it to your sport is one of the things that increases satisfaction when shooting airguns.
Understanding scope adjustments
Most shooters know there are both vertical and horizontal adjustments available on a scope. They’re called elevation and windage adjustments. Here are some facts about adjustments that you may not know.
First of all, no scope adjusts exactly by a quarter minute of angle or an eighth minute of angle. When they say these things, scope manufacturers are only making approximations. The scope adjustments depend on the thread count of the adjustment screws, and the manufacturer will round this up or down to give an approximate distance the crosshairs move. This is given in minutes of angle, and the most common understanding is at a 100-yard distance, where a minute of angle is very close to one inch. So, a scope with ¼ MOA adjustment clicks is supposed to move the point of aim by a quarter-inch at 100 yards. It sounds great until you understand that everything is an approximation. The real distance that the crosshairs move with one click of adjustment may be 0.311 inches, but no scope manufacturer is going to put that on the box. So, they write that the scope has quarter-minute clicks, and you work it out when you sight in — unless you’re anal, which is where some shooters get into trouble.
These shooters arrive at the range with their scoped rifle and a notebook to record all the scope adjustments. Man — that is a heartbreak in progress! What will happen, if they stick to it long enough, is that they’ll discover that their scope actually adjusts by 7/19 of an inch per click. Most of them see the futility of trying to do it by the book and default back to adjusting the scope until their rounds strike the paper where they want them to…or as close as their scope can come.
Now, let’s talk about stiction, which is the scope’s unwillingness to move after being adjusted until it is hit with a large amount of vibration. Said plainly, the scope tends to stay where it was before the adjustment until the gun is fired several times and it finally “settles in” to the new adjustment. Put an eager-beaver shooter on that scope and have him try to sight it in, and you have the recipe for disaster. He’ll keep adjusting the knobs, all the while the scope is lagging behind each adjustment by two or three shots. The result will be a scope that wildly changes its point of impact as the frustrated shooter fails to comprehend that he’s causing the problem.
When a scope is adjusted, sometimes it takes several shots for the adjustments to be fully realized. This is called “stiction,” which is the resistance of the scope’s parts to movement after they’re adjusted. In this case, the first shot was to the left and low, where the scope had been before adjustment. Shot 2 moved to the right and up, and shots 3 through 5 are in a tight cluster in the new point of impact.
Not all scopes suffer from stiction. Of those that do, all won’t suffer by the same amount. Each scope must be taken as a unique entity, and the shooter has to have patience when adjusting it. This is the one time where three-shot groups are valid because they give the scope time to move to the new setting. But if the shooter doesn’t realize what’s happening, it can look like the scope is no longer able to hold a group because a three-shot group from a scope with a lot of stiction will look like a wild pattern. All you have to do is to continue shooting the gun, and things will settle down, again. But some shooters don’t have the patience for this.
Look for part 2 tomorrow.