Troubleshooting & Maintenance
What is Parallax and How to Adjust Parallax (on a Parallax-Adjustable Scope)
Well, have you ever looked through a higher power scope and noticed that if you move your eye off center to the edge of the exit pupil, the reticle seems to move across the target? Well, that shift happens when the parallax setting is not properly adjusted for that distance. Some have mistaken the parallax adjustment as a focus or even a range finder, but it is neither of these. The parallax adjustment, when set properly will insure that the reticle is positioned correctly on the target; as though your crosshairs are a part of the target, unmoving, as if they were painted on, just for you. Of course if your scope is not a "target" or a "varmint hunting" rifle scope, you probably don't need to be concerned with adjusting the parallax setting. In most hunting scopes the parallax is negligible, in fact I have a good friend that hunts regularly and he didn't even know what I was talking about when I asked him. I don't hunt, but I love to spend a Saturday at target practice. So to me, any small increase in accuracy is definitely welcome.
Most of the higher power scopes, with a power of 12 or more, will have an adjustment ring at the end of the Objective bell (the end closest to the target). Usually the parallax adjustment ring has the suggested settings printed on them, so you can just dial in the range you're shooting from. The problem is these suggested settings are rarely as accurate as they could be. So why should you go through the trouble of getting yours "just right"? Why not just use the suggested setting? Even if you're a great shot, you could easily shrink the size of your groups by as much as 30%, just by taking the time to properly set the parallax adjustment on your scope. Many shooters don't even realize that even with a few adjustments they could greatly affect their shooting performance. Let's face it, the documentation that came with your scope isn't a real blessing when it comes to learning how to use it, they just assume you already know.
Now that you have an understanding of what parallax is, it's time to fine tune your scope for increased accuracy. I'm going to assume you have already zeroed in your scope and that it's properly sighted in. You will need to set up your rifle so it is securely positioned on a bench. A shooting rest with a vise would be best. Dial in the suggested setting on the parallax adjustment ring for the range that you're shooting from. Now, look through the scope and shift your eye back and forth, left and right so you can see if the crosshairs seem like they are moving across the target. Experiment with the adjustment ring until you have eliminated the illusion that your crosshairs are moving. When you think you've got it perfect, take a little white-out liquid paper and make a mark on the parallax adjustment ring so you'll know where to adjust it later. Some people paint their mark or score it into the metal, but to start with I prefer something that's not so permanent until I'm absolutely certain about the position. Next, go ahead and take three to six shots and see how your grouping has improved.
You may repeat the process depending on your shot range and other needs.