By Philip Mahin
Last time we adjusted a scope for focus, this time we will adjust an objective lens to be parallax free at a specific distance.
There may be different ways to adjust your specific scope but the one I have here to demonstrate with is on the front of the scope. This part is called the objective lens and basically the mechanism rotates just like the ocular lens does to focus the eye piece. This addition gives the scope an ability to adjust out any parallax that might be found at a specific distance. What is parallax? That is the movement of the target from the crosshairs as the eye moves away from the center line of the scope. Depending on the scope, this movement may not be much, but it may be enough to miss a target of importance at a far-off distance.
The non-adjustable Leupold scopes that I have were factory set to be parallax free at 150 yards, but you can see the effects with any scope. Just put up two targets at different distances, one at say 75 yards and the other at 150 yards. With the scope mounted solid to whatever is handy, focus it on the 150-yard target with the 75-yard target still in the view of the scope. Move your head slightly and the 75-yard target will move with it. With this adjustable version, I can focus on the 75-yard target and see the 150-yard target move. This is parallax in a nutshell.
I will admit, I don’t own a lot of adjustable objective scopes. My style of hunting doesn’t require it. This scope is used in target shooting at known distances, when I have plenty of time to set it up correctly. It is also the one I used to get a 0.380” group size at 100 yards with our 69gr TMK out of a typical hunting rifle. I’m not willing to admit I’m that good of a shot, just that I used good components! Till next time, have fun shooting.