Parallax Adjustment On Scopes Without AO

Discussion in 'Long Gun Accessories and Optics' started by Phydeaux642, Aug 30, 2021.

  1. Phydeaux642

    Phydeaux642 Member

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    I would like to try my hand at shooting small groups at 100 yards with .22lr. The scope on my rifle at the moment is a Vortex 2-7x rimfire which works out great at 50 yards but not so much at 100 with my old eyes.
    I really can't spend the money for a new scope right now but I do have a Vortex 4-12x scope just setting around. It's a centerfire scope and I know the parallax for it is set for 100 yards vs 50 yards on my other scope. The 4-12x scope has no parallax adjustment but I have read where people do some adjusting to the objective end of the lens by turning a lock ring or something. Has anyone here done this with a good end result? And, if so, is there some detailed instruction on how to do this?

    EDIT TO ADD: I will still mostly shoot at 50 yards, so, that's why I was wondering if the 4-12x scope needs the parallax adjustment changed.
     
    Last edited: Aug 30, 2021
  2. CoalCrackerAl

    CoalCrackerAl Member

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    I have used plenty of scopes with a fixed parallax. And had good success. Without doing any mods to the scopes. Just adjust the focus to suit you.
     
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  3. TimRB

    TimRB Member

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    Make or buy a device that forces you to look through the center of the scope. If you do, parallax will never be an issue. Fact is, if you do the math you'll find that it's not a very big issue in the first place.

    Tim
     
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  4. The Glockodile

    The Glockodile Member

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    Last edited: Aug 31, 2021
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  5. 243winxb

    243winxb Member

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    Your 4x12 scopes paralax is factory set at 100 yards.

    The eye piece can be adjusted- 20210830_212825.jpg
     
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  6. Laphroaig

    Laphroaig Member

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    Invest in a Butler Creek lens cap. I've found that a 1/4" hole drilled in the center is a good size at 4X for both field of view and keeping your eye centered. If you are mindful of keeping the reticle centered you won't really need anything at the ranges you are talking about.
     
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  7. jmr40

    jmr40 Member

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    Don't overthink this. I don't have any scopes that are designed specifically for 22's. I use basic scopes meant for centerfire rifles that have parallax set at 150 yards on all rifles. I use them on 22's and shoot them at ranges from 25 yards to 250 yards with no problems.

    Parallax is one of those things that just isn't an issue for 99% of shooters. As long as you get your eye directly in line with the scope it has zero effect. And at most you're talking about point of impact changing by around 1/4" at 100 yards, less than 1" at 500 yards if you are looking through the scope at an angle. It takes a pretty accurate rifle, ammo, and trigger puller for that to be a problem.

    Don't confuse parallax with focus. They are not the same thing. Some scopes focused at 50 yards won't be focused at 100. I do find that a scope with a fast focus adjustment ring does help. And some more powerful scopes may never focus up close if set on high magnification. I have one 4-12X scope on a 22 that will not focus at 50 yards if it is set above 10X. I simply run out of adjustment. But 10X is more than enough at 50 yards.
     
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  8. LoonWulf
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    LoonWulf Contributing Member

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    I do it fairly regularly on scopes that lack an adjustable objective focus. Ive had to reset parallax adjustable/side focus scopes as well.
    On older scopes the lock ring (the ring infront of the end of the scope tube) will usually unscrew, and with that removed the assembly that holds the objective lens can be rotated in or out to suit your needs.
    On the newer ones I've messed with, the scopes are assembled with some sort of tacky glue. I had to heat the end of my X5 to get the ring off, and then keep it warm so I could adjust the lens assembly to where I wanted it.....actually a very similar process to removing the lenses from automotive light housings, I wonder if they are using a similar glue on scopes now.....
    I need to redo one of my centerfire scopes to run on my dads airgun, I can do a short video of it if you want.

    adjusting the ocular lens is specifically for adjusting the focus on your reticle, not really for focusing your image.....or at least that's what I've always understood?
    I can often get a clear image by messing with it, but in doing so I completely lose the reticle.
     
  9. HankC

    HankC Member

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    People do that to use a regular scope on air rifles shooting at 10-30 yds. I have done that on a few scopes. Turn the front lense out to shoot short distance. At low magnification, such as 4X, should be fine if shooting at 50 yds. When you break the seal to turn the lense, moisture intrusion may be an issue.
     
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  10. velocette

    velocette Member

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    Laphroaig and others have it right. the hole in the center of the cap will force your eye to center itself, thus removing parallax. This is commonly done by precision shooters with a clear plexiglas disc with the same1/4" hole inside a slip on lens cap to center it. Further note, 23winxb is correct in how to focus the reticle, however, that will have no affect on parallax.
     
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  11. tbs

    tbs Member

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  12. Varminterror

    Varminterror Member

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    Lots of bad on this.

    Occular adjustment is meant to focus the reticle plane to your eye. Your eye never changes position behind the scope, so this should never change. Ever. When the reticle is clear at one distance but blurry at another, this is indication of parallax discrepancy in the scope: the shooter’s eye is able to overcome the inaccurate parallax focus and bring the target into clear focus, but because the target image and the reticle planes are no longer coplanar - so ONE will always be blurry when the other is focused. Effectively, the shooter is looking deeper or looking shallower into the scope to focus the target image, which should not be happening. We should always be focusing on the reticle plane, and our parallax correction should be bringing the target image to the reticle plane. THIS is why we have adjustable objectives or side parallax focus in our scopes. We need a way to ensure the target image and the reticle image are coplanar.

    Also, it is incorrect to say the maximum parallax error potential is only 1” at 500 yards. For a 40mm objective with a 100yard fixed parallax, the maximum parallax error is 3.1”. Max error (in mm) = 1/2 * Diameter of objective (mm) * absolute value of (target range - parallax setting) / parallax setting, so 40 / 2 * abs(500-100)/100 = 80mm, 80mm = 3.15”. Even using a 150yrd fixed parallax scope, the max error potential in a 40mm is 1.8” at 500yrds.
     
  13. ms6852

    ms6852 Member

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    I shoot thousands of rounds a year in 22lr at 200 yards, and for me I find that AO or parallax adjustment is a necessity, regardless of what others have stated. So for these reason, my most powerful scopes are on 22lr rifles and a prerequisite is AO and or parallax adjustment. I personally want to know that if my bullet impacts are all over the place that it is not me and that it is the round or the wind affecting my shooting. You could use a peep sights for a hundred too and you would not have to worry about parallax. I shoot my 513T and 52C at 100 yards and used to shoot them at 200 when my vision was good. Now I use the huge shoot NC targets meant for 200 at 100 yards where I can distinguish the red center.
     
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  14. Varminterror

    Varminterror Member

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    @Phydeaux642 - let’s get specific about your two scopes in question:

    First, you mention the Vortex 2-7x Rimfire scope, which I know would be the 32mm. But the other Vortex 4-12x, you don’t mention whether it’s a 40mm Diamondback or a 44mm Crossfire (safe assumption it’s not the 50mm AO).

    So let’s say you shot either of these as is, at the “wrong” range for its native parallax, or you adjusted either scope to the other range, then shot it back at the original parallax range...

    I shared the formula for maximum potential error induced by parallax above.

    Your 2-7x left at 50yrd but shot at 100yrds: 32/2*abs(100-50)/50, converted to inches = 0.63” at 100yrds, 0.60moa.

    Modifying your 2-7x to be 100yrd focus, but then shooting it back at 50yrds: 32/2*abs(50-100)/100, /25.4 = .31” at 50yrds, .60moa.

    Same potential error at the “wrong range.”

    If you have the 40mm Diamondback which is focused at 100, firing at 50yrds, then 40/2*abs(50-100)/100 /25.4 = .39” at 50yrds, or .75moa.

    If you modify that Diamondback to focus at 50yrds then shoot it at 100, you’d have 40/2*abs(100-50)/50/25.4 = .79”, or the same .75moa.

    If you have the 44mm Crossfire, add 10% to these 40mm results = 0.83moa max potential error.

    We’re simply shooting too short for major differences shooting in front or behind of the focus range...

    So we see the maximum potential error if you stick with your 2-7x is .6moa, or if you change to your 4-12x, you’d at worst see .75moa influence.

    Errors aren’t additive, so you won’t see a full extra .75moa into your groups, but you may see 1/2moa additional error since eye misalignment is typically unidirectional (for example, always tending left) whereas your raw group dispersion error is omnidirectional.

    One option, without cost, would be to zero both scopes to their respective ranges and swap the scopes when you shoot either distance. The best option is obviously to buy a scope with adjustable parallax focus, and eliminate that potential .4-.5moa extra error altogether.

    I’ll also caution, there’s considerable risk in accidentally scratching your lens and/or purging your dry gas by compromising your lens seal when trying to adjust the parallax focus of a fixed parallax scope. Doing it once is one thing, but don’t let yourself believe you could change it back and forth a few times per month or even per year as if it were an adjustable objective optic.

    So honestly, flip a coin. Whichever you prefer or can see best with, use. You’re talking about .15moa difference between maximum potential error whether you use one or the other. If you’re shooting EXTREMELY small groups, with a fixed parallax Vortex, to the point .15moa will be noticed in your groups, then use the smaller scope. I’ll tell you for certain, I’ll hold better than .15moa tighter by using a 12x at 100yrds instead of a 7x optic, just by having a more consistent aiming picture, so I’d shoot the 4-12x, and ignore the parallax estimate.
     
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  15. Phydeaux642

    Phydeaux642 Member

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    @Varminterror, thanks for the detailed post. The scope is the Sonora 4-12x44, which from what I gather is basically the Crossfire (got a really good deal and picked it up for future use). I've been looking at scopes with adjustable parallax but really can't afford to spend a lot to get what a lot of people recommend.
     
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  16. TimRB

    TimRB Member

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    Quoting my own post again--that seems wrong somehow. Anyway, since I have nothing better to do...

    If you decide to make something rather than buy, it needn't be fancy or expensive.

    IMG_0191.jpg

    IMG_0190.jpg

    I found a piece of clear plastic in my junkbox, drilled a quarter inch hole in it, and shaped it to fit into my scope eyepiece. The black rubber part is a section of an old mountain bike inner tube.

    Works great.

    Tim
     
  17. Walkalong

    Walkalong Moderator Staff Member

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    Another easy way to center your eye is to be a little too far back or forward so you can see a black ring around the edges of the eyepiece, and then just make sure it is even all the way around.
     
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  18. stillquietvoice
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    stillquietvoice Contributing Member

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    I don't either, I have 3 low end 3 - 9 x40 scopes on my 22 lr's. Can't shoot much above 6x at close range, but at 6x I can see well enough to shoot small groups, with good ammo, not the thunder duds I have in stock. Don't usually shoot rimfire over 50 yes. What I do have is a low dollar Bushnell banner 6 - 18 x 50 ao albeit on a 223 bolt action that I can see clearly up to 16x at most ranges from 50 to the 300, above16 there is some edge distortion, but that isn't too bad. Was out shooting with a friend a couple weekends ago and used it as a spotting scope at 50 yds set at 9x while he sighted in his ar
     
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  19. Atjis

    Atjis Member

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    @Varminterror I really appreciate your detailed responses regarding parallax and how objective size and distance to target factor into computing the max error, but how does magnification factor into that equation? It seems like the general wisdom is that higher magnifications increase the error potential, with one site even saying that the magnification number directly multiplies the margin of error in parallax. So 12x power scope zoomed all the way in might increase the margin of error from 1.8" at 500 yards to 21.6"? That's seems pretty incredible to believe. Can your equation account for magnification?
     
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  20. Varminterror

    Varminterror Member

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    Mathematically and empirically, I am convinced “general wisdom” is wrong on this topic.

    I have not been able to personally confirm parallax variability with magnification, and have never been able to find, despite searching, physical (mathematical) evidence which supports that increasing magnification actually changes potential for parallax error. But I have been able to disprove it on multiple occasions.

    Just for fun, since it is Friday afternoon, I called Leupold, Burris, and Vortex just now before responding to see if my experience and mathematical understanding are incorrect - and all 3 confirmed that increasing magnification does not increase maximum parallax error. The Vortex rep even went as far as to take a Strike Eagle and a Viper PA (FFP and SFP, respectively) out to a window on a fixture and vary the magnification with incorrect parallax, observing the maximum swing of the reticle against the reference - the error side to side was the same at all magnifications in both the SFP and FFP scopes. I’ve done the same test with my own scopes in a tracking fixture with a laser reference, and have observed the exact same response - no parallax error change when increasing or decreasing magnification. (Bushnell office was closed, but I tried them also).

    Plainly, it doesn’t happen. Maximum parallax error doesn’t care about magnification change. It’s an old wives’ tale, and that myth is BUSTED.
     
    Last edited: Jan 14, 2022 at 3:43 PM
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  21. 12Bravo20

    12Bravo20 Member

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    If you are having to adjust the parallax when you change zoom in or out with a variable power scope, something is wrong with the scope. I had a scope that would do that and the manufacturer wanted it back right away so they could replace it under warranty.
     
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  22. Varminterror

    Varminterror Member

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    It’s relatively common (as a defect) for a scope to need parallax correction as magnification is changed, but that’s a different thing than we’re discussing in the influence of magnification change upon maximum parallax error. I do also think a lot of shooters experience the user error of incorrect ocular focus, which ends up forcing parallax corrections as magnification is changed. Still again a different thing than this false belief that “parallax error increases with magnification.”
     
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  23. 12Bravo20

    12Bravo20 Member

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    All true and I agree with what you are saying. I brought up my 1 bad experience to show that if has to be adjusted as the zoom is changed, the scope is most likely defective
     
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  24. Atjis

    Atjis Member

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    @Varminterror I really appreciate your reply and further explanation. More than I was hoping for! That makes so much sense, even though it goes against a lot of what I've read. One thought I had was that if magnification did impact parallax error, you'd need a separate side focus knob to adjust based on magnification, but that's not how it works. The side focus adjustment on long-range (and high magnification) scopes is adjusted solely based on distance to target. Again, this makes sense when you look at what the side focus does: it moves the reticle so that it is the correct distance from the objective lens inside the scope so that the image your eye sees being formed of the target is at the same spot inside the scope as the reticle. Once that is established/lined up, whether you increase magnification and make the whole picture you're seeing look bigger or smaller doesn't change where the image is being being formed inside the scope because it doesn't actually make you any closer to your target. So all the angles of reflection that cause parallax remain the same.
     
  25. Walkalong

    Walkalong Moderator Staff Member

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    The dipoter adjusts your eyes focus on the reticle, which I believe is fixed, whether wire or glass etched. The parallax adjusts the image of the target to the same plane as the reticle, eliminating parallax error. If the diopter is set correctly, the image should be clearest where parallax is removed.

    Someone please correct me if I a wrong about the reticle.
     
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