The term ‘parallax’ is often used to describe rifle scopes, but few people know what it means or how to correct it. Parallax refers to a situation where the focal plane of the object in the scope is offset form the reticle. It is essentially an optical illusion that has to be corrected.
Parallax is very different from focus, and it is important to understand that. Parallax compensation does not change the focus of the reticle or the image, but rather movies the planes where the two objects can be seen in focus so they share the same plane.
You will find that most high powered scopes typically come equipped with a side-mount turret or adjustment ring located on the objective bell, allowing you to move the focal plane of the target and reticle to eliminate parallax altogether.
Some of these rings or turrets are marked with a variety of distances, usually ranging anywhere from 50 yards to infinity, which is meant to indicate the distance necessary for eliminating parallax.
Even though it is true that these factory settings can be very helpful when trying to solve parallax, they don’t always do the trick. It is sometimes necessary to determine the proper setting manually by using 50 yard increments, marking the settings on the scope.
It is very important to get a completely accurate parallax setting because the amount of parallax significantly increases with magnification, increasing the margin of error at higher powers.
If you want to know how to get consistent parallax compensation with your rifle, you can follow these steps:
1. Zero the scope on your rifle
2. Make sure your firearm is in a stable configuration and aimed downrange at your target. You can use either sandbags or a machine rest.
3. Choose a target that is located at the maximum of your shooting range. Ideally you will want to choose a target that is around 1,000 yards away, though you can choose one at a shorter distance and it will still work well.
4. Set the magnification on your rifle’s scope to its maximum setting.
5. Sight through the scope
6. Shift your gaze slowly while you are searching for movement of the reticle in relation to the target
7. Adjust the focal planes using the parallax compensation turret or objective ring until the reticle does not move at all when you begin to shift your gaze.
8. Use a fine marker to mark the point on your turret for the ideal range.
You will be able to repeat this process at a variety of distances by simply moving the target closer and repeating the above listed steps. By permanently marking the positions on your turret, you will be able to consistently return to that point whenever you want and without any confusion or difficulty.
When you are adjusting parallax using a side-mount turret, you will need to start with the turret set against the stop past infinity and turn it to the appropriate setting.