Rifle Scopes  Parallax please explain


PX Member
Feb 12, 2017
I guess I just don't completely understand it. Is there a point where it starts to make a difference? Like I only need to adjust past 500 yards? I see some scopes have yardage marked on the adjustment and others do not. So how does one know where to adjust on the unmarked adjustment? I don't remember reading this on Scout and I can't figure out how to search on here.


Gunny Sergeant
PX Member
Feb 12, 2017
Parallax is defined as the apparent movement of the reticle across the target when the eye (or head) is slightly moved.
Best way to find out if you have parallax is if you properly focus the optic, stabilize the gun completely, and without touching the rifle look through the optic and move you head slightly up/down and left/right. If you see the reticle move across the target, you have parallax, adjust the parallax until you no longer have any movement. Some optics have a side focus where the target will come into focus when the parallax is adjusted for the target. All you're doing is putting the reticle on the same focal plane as the target.
You need to adjust the parallax for each target, not each range.
The yard or meter increments are very accurate, but are not end all be all. Those serve as adjusting the parallax in a pinch, that's the way I see it as, at least. If I have the time I will adjust the side focus or parallax knob accordingly.

Edit: you can use a piece of tape and mark each increment, as long as you have accurate range measurements.
Last edited:
  • Like
Reactions: longshot2000


Gunny Sergeant
PX Member
Jul 1, 2012
Philadelphia suburbs
With a properly functioning scope that has the diopter set correctly for the shooter's eye, parallax is eliminated when the target is in focus. Focus the target, shoot.


Sniper's Hide Dealer: CHARLIE'S
Commercial Supporter
PX Member
  • Feb 19, 2017
    Northern VA
    excellent replies. LaRue had a very easy to read "article" on Parallax in their recent catalog. Some facts that I have found helpful (much has been said above):

    1) spend the time, once a year to focus your diopter. This takes time. Focus the reticle ONLY. Focus once, put it down, and give it a quick glance, then focus again. Repeat. Best to look at a white sheet of paper. Focus on high power and low power. If you can do this under 2 minutes, you are not doing it correctly. Do it over. Younger eyes are more forgiving, and thus the focus needs to be done more. Those over 40, less repeats.

    2) the yardage on the parallax knob is relative, and most often a very (very) rough reference.

    3) If you did #1 correctly, then parallax can be seen as the "focus" of the target, so use the left knob to focus the target. If you do this, you are 90% there.

    4) finally, see if moving your head slightly, while on a target, if the center moves off the target. If it does, fine tune the parallax knob, until it does not. If you do this, and go back to #3, and still the target moves off the center, you have a bad scope.

    5) even with a bad scope (in combat, you cannot return for warranty repair), put the scope forward, until the eye ring shadow appears. Then center find the target, on the reticle, with the shadows even around the eyepiece. Now, shoot.

    Good luck.


    PX Member
    Nov 15, 2010
    Castle Rock, CO
    And yes, if you have parallax at closer ranges you may have issues with POI. Some scopes are very easy to adjust parallax out, some are more finicky. It is a pretty simple thing to check once you get the technique (explained above) down.