DIY Parallax adjustment

Grizzlypeg

Grizzlypeg

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Here's one of those nothing ventured, nothing gained, but not for everyone projects. Many fixed parallax, centrefire scopes that have the parallax set for a distance beyond that which we typically shoot a rimfire can be easily adjusted. This will probably void your warranty, and if you impliment some hard tools, be careful not to scratch the scope's finish or the lens surface. I am able to do this entirely by hand and no tools were required. A piece of sticky rubber or a band wrench may be helpful to loosen the ring initially. Some people have used a thin metal ruler to turn the lens (group?). I didn't find that necessary.

Step 1. Does your scope have a separate bezel piece on the objective like this?

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If so, and you are willing to proceed:

Step 2: Unscrew the bezel.

It is effectively a lock ring that hold the objective lens group in position. Standard right hand thread, lefty loosey, righty tighty.

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You will see that it is threaded onto the end of a threaded inner tube. This tube holds the lens group in position and this tube is itself, threaded into the scope body and can easily be turned. Its is sealed with grease, if the scope is at all decent, it has an O ring sealing off the atmosphere from the inners of the scope. You will only need to turn it slightly, probably less than half a turn. Don't unscrew it fully, its not necessary and you will let moist air in, which may later fog the scope under cold conditions.
 
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Here is the exposed threaded end that you will want to turn to adjust parallax. On my scope, you turn it outwards slightly to reduce the distance setting from what was probably 150 yards, down to 50 yards, if that's what you desire.

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Step 3: Adjust parallax: You will want to set up your rifle on a rest at the range. You will carefully turn the threaded portion (outwards most probably) until shifting your eye around behind the scope produces a minimum of parallax (apparent change of aim of the reticle on the target).

Step 4: Once set, you carefully reinstall the outer trim ring, make sure the parallax setting hasn't changed from the inner tube accidentally rotating, then tighten down the lock ring and you are done.

The scope shown in the photo is an inexpensive Bushnell fixed power scope. I am told that Leupolds have exactly the same design of the outer bezel being the locking mechanism.

You can make up a simple tool from a piece of thin metal, like a metal ruler, to fit into the slots in the end of the tube. That way you can just slightly back off the lock ring, make the adjustment, and then retighten down the lock ring.
 
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I thought scopes were gas filled to prevent foggging. Would this not break the seal and make the scope possibly fog if taken from area of differant temperatures?
 
Radar said:
I thought scopes were gas filled to prevent foggging. Would this not break the seal and make the scope possibly fog if taken from area of differant temperatures?
Click to expand...

Break the seal? Possibly, but probably not. The seal is made by grease on the threads and likely an O ring. Turning it 1/3 turn should not compromise the seal. I'm not saying the seal is identical, but you rotate the power ring and the ocular focus ring without compromising the seal, although they are no doubt made specifically to be a rotating seal. As well, if Leupold's factory custom store will alter parallax for $15.00 in the US, do you think they purge and refill the scope? I'm told Leupolds are built the same way, loosen the bezel and turn the objective lens group to set parallax.

Definitely understand there may be risks in doing this, but this offers a way to make that old centerfire scope you have lying around work better on a rimfire.
 
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"I've done this plenty of times, never an issue"

I did too, some scopes have "inside the bell" lock ring and their lens group
does not extend outside the bell, I was able to turn the lens group inserting
my nails in the notches on the rings.

(It was an old Weaver Mraksman3-9 x 32)

Jocelyn.
 
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