Adjusting Parallax on Non-AO Scope

By Archer | Scope

Mar 27
Mounted Rifle With Scope

Adjustable Objective Scope VS Non Adjustable Objective Scope

If your rifle scope features an adjustable objective (AO), you won’t need to perform anything on it because it has the ability to make parallax adjustment.

However, these types of scopes are expensive and you may not have sufficient budget for them.

Do You Know?
Higher end scopes have a third turret/knobs, often referred as side focus. This is a very useful feature as it allows the shooter to read the settings with minimal movement of the head. 

For starters, the other alternative is to use a non-AO scope. This article will show you how to change parallax on non-AO scopes.

How Does Parallax Occur?

Parallax happens when the image and the reticle are not on the same central plane causing movement of the reticle across the target.

To eliminae the problem, you will need to:

  1. Properly focus the reticle to the shooter’s eye
  2. Adjust the focus knob.

Adjusting parallax on non-AO scope aka fixed objective scope is not exactly nuclear science. A few simple steps will get the job done. Nevertheless, you will need to be extra careful to avoid wrecking the scope in the process.

Take Note
Nitrogen will escape if you take the lens carrier out of the scope after the 1/4″ lock ring is removed leading to expensive factory repair work.

Long Range Rifle With Scope
Image Via Flickr CC: Jun Wang

If you have a fixed scope, you will discover that you have one parallax-free distance due to its single power setting. Now, this is what you wish to change, don’t you?

If you are on a tight budget, you may go for a variable low power scope or a cheaper version of a fixed power scope. Most of these scopes have no adjustable objective knobs to enable parallax adjustment.

Well, I’m sure that you have a different range in mind other than the factory settings on your rifle scope.

Take Note
Low power variable scopes must be set to the highest power during the entire adjustment.

Adjusting Parallax on Non-AO Scope

Step 1: Locate the ¼ inch Lock Ring

You probably own a Tasco, Nikon or Simmons, or any other delicate types. To find the ¼ inch ring, focus your eyes on the bell of the scope. The bell of the scope is that part at the opposite end of the eyepiece.

This is important because you have to take off the lock ring so as to adjust parallax. I recommend that you pay the local hardware store a short visit to purchase a strap wrench. Make sure it has a rubber strap to protect your ring from any damage.

You may not easily spot it because it is finished to appear smooth or matte to ensure it is not too obvious. You will soon realize it is firmly locked in place by some seal.

Step 2: Remove the Lock Ring

The lock ring may not come off easily. You may use a damp wash rag to enable you have a better grip on the scope without messing it. You may also grasp it using the rubber material that is used for lining shelves.

Once you get a firm grip on the scope, proceed to gently turn the lock ring in an anti-clockwise manner until it comes off completely.

Step 3: Adjust the Objective Lens Ring

Having carefully removed the lock ring, peer into the scope and you will see the objective lens nestling inside yet another ring. This new ring has two slots opposite each other. This is the ring you need when adjusting parallax on non-AO scope.

You will need a thin but strong bar of steel to change the object the same way you would for an adjustable objective scope. Be extremely cautious not to scratch the lens. Scratching the lens may not hurt you but definitely, your wallet will.

Some scopes have this ring recessed. To access and adjust it, you may choose from several home-made tools. You can trim a steel ruler to fit into the inside of the scope. Alternatively, a spark plug wire removal tool but you have to file it down for a good fit.

I know a broad smile of satisfaction is now lighting up your face. But you are not done just yet. You have been adjusting parallax on AO scopes for half of your adult life. That was relatively easy because the AO scopes have been calibrated according to shooting ranges.

You should have noted that manufacturers don’t bother marking non-AO scopes to reflect distances. They are probably not expecting you to adjust them anyway. You may require a little adventure at this stage.

Step 4: Adjust the Objective Lens Inwards

Before trying to make any adjustments, note the positions of the two slots on the objective lens ring. You may need to return everything to their original position later. Start by adjusting inwards.

I prefer changing inwards because, this way, there is decreased the possibility of tampering with the airtight seal of the scope. Having made the inward adjustment, you can now check parallax. Has it increased or decreased? Move in or out as necessary.

Step 5: Re-adjust the eyepiece

You will realize that changing the settings of the objective lens has caused the eyepiece to lose focus. You have to readjust it by undoing the eyepiece lock ring. Adjust it to re-establish the focus for the reticle and the target.

When everything is well, you will have the ability to see the goal over the scope as well as through it without changing your eye focus. You have a clear line of sight now and can aim accurately at anything without further ado.

Step 6: Re-fix the ¼ inch Lock Ring

Are you satisfied with the new setting? Do not forget that you have one ring lying on the table. Put in back to the scope and rotate it into place without turning the objective lens.

It is possible to adjust parallax on a second non-AO rifle scope, but you must be careful. Carefully remove the objective lock ring and rotate the objective lens, then check for parallax. Once done, readjust the eyepiece to the new settings.

You may prefer buying the more expensive AO scopes and have no problem to adjust parallax manually. Adjusting parallax on a non-AO scope is delicate, and damaging any of the internal parts will require you to purchase a new scope.

I know you are now ready to pull your non-AO rifle scope apart. Just be careful not to scratch the objective lens, or let the nitrogen in the scope escape. Otherwise, you can go ahead and turn your cheap scope into a complicated affair. Good luck!

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