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Thread: Comparative Study of Red Dot Sight Parallax

  1. #41
    I hate to dredge up an old post but the relevance and lack of SME input in other related posts isn't cutting it.

    I recently bought a 3rd RMR Type 2 and this one has way more Parallax Shift Relative To Head Position then my other two RMRs.

    I keep hearing this "works fine for me" or "Cool guys uses brand ________ so it must be perfect" but that just shows a lack of exposure to the conditions that cause the error in the first place.

    If you shoot in a flat, 2D environment with stationary targets and can assume an ideal firing position and grip every time you pull the trigger you'll never notice that your dot moves all over the damned place relative to your head position. However if you train in a 3 dimensional environment and practice things like firing from a ladder, laying flat on your back, prone, weak hand "wounded", from inside a vehicle, underneath a vehicle or in some other cramped area where you can't extend your arms fully the parallax shift thing becomes a real PITA.

    I was an early adopter of the Aimpoint T1 and have kept the same 4moa T1 turned on almost continuously since GW Bush was president other than an annual battery change. I've done some great shooting with that little T1 equipped Colt over the years and I'd still bet my life on that setup BUT when doing headshots in a CQB range scenario I can definitely miss the badguy by 3-5 inches or worse yet hit the hostage part of the target if my face comes off the stock even a little bit because I'm in an unorthodox shooting position.

    Reducing/Eliminating Parallax Shift Relative To Head Position needs to become a top priority of RDS manufacturers who cater to the defense, law enforcement and personal defense segments of the market but it requires someone other than just the Green Eye Tactical guy to get their attention and the only guy making a concerted albeit unscientific attempt at including Parallax Shift in his optic reviews/tests is a youtuber called JRR Armory. I wish he would adopt the Green Eye Tactical targets and method of assessing this but something is better than nothing I guess..

    https://www.youtube.com/user/jobane2...query=parallax


    Someone needs to go beyond what dopushups has done and make a master list of every RDS type optic in the market ranked by how much of this PARALLAX SHIFT RELATIVE TO HEAD POSITION is present in each optic at common shooting distances(5, 15, 25, 50, 75 and 100 meters/yards so end users can get an idea of what their pistol or carbine will shoot like when laying on their side trying to shoot under a car or kneeling at a range barricade with a slot that's just a hair too tall to achieve a "perfect" kneeling position .

  2. #42
    Chasing the Horizon RJ's Avatar
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    Old thread, but bear with me: @rdtompki started an interesting thread on a specific issue related to RDS Training Buzzwords.

    https://pistol-forum.com/showthread....ning-Buzzwords

    I got into the weeds on a discussion on parallax, which led me to this thread. So as not to clog up that topic, I thought I'd put some more thoughts here.

    I am pretty new to dots, and only transitioned last year from iron sights. I have zip for experience with rifles, all my shooting is with pistols, at 25 and closer. So the context of this post stems from an observation I had, where if I move my head around, the MRDS on my Holosun 507c seems to "move" on the target, even though the gun is clamped on the bench.

    Video of this on my phone seems to confirm:



    As say, this discussion led me back to this 2017 study, and this thread.

    Being a retired engineer, I have the time and interest to replicate some aspects of the study. Namely, take my optics, download or replicate the control target, and set up a simple visual observation platform with the guns clamped in some kind of jig at 25 yards, in my house. Then I'll record some V and H deviation numbers, using the study test protocol, with the three optics I have (two Holosun 507c's and a Holosun 507k.)

    It might be interesting to get others to do the same. I'll sign up to "compile" the results, if any, for whatever use it might be. I'll certainly summarize my findings, for what they're worth. I'll be back with more info as and when I get a chance to develop this further. Obviously it's my time I'm wasting, and probably not of interest to anyone but me, but I find this stuff interesting.

  3. #43
    Edit
    Pointing at cardboard things.... CO GM, working on PCC.

  4. #44

  5. #45
    Chasing the Horizon RJ's Avatar
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    Quote Originally Posted by RJ View Post

    ...Being a retired engineer, I have the time and interest to replicate some aspects of the study. Namely, take my optics, download or replicate the control target, and set up a simple visual observation platform with the guns clamped in some kind of jig at 25 yards, in my house. Then I'll record some V and H deviation numbers, using the study test protocol, with the three optics I have (two Holosun 507c's and a Holosun 507k.)
    Soooooo...I had a few minutes free time this afternoon with no honeydo chores assigned. Woohoo!

    I went ahead and set up a test bench, sorta kinda, in my house. My place is not really that big, so I opened the door to the garage and placed a sighting target on the door, on a magnetic hook. I designed the target to mimic the one in the study, but realized after I did that the study author provides one for download. Its a 1" grid with a 4" disk, consisting of the disk and a 1" white center. I also put a small DC work light shining on it.

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    75' away, more or less, at the end of the living room, I sat behind a small table, with each of my optic equipped pistols clamped in a soft vise, padded/setup so that the dot rested on the center of the sighting target. I set the dots (507c's to dot only) to manual, minimal brightness, and sighted down the optic.

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    Centering the dot on the target, making sure my eye was also centered in the optic (as per normal), I then moved my eye slowly to the top (T), bottom (B), left (L) and right (R) of the glass, observing any shift in "where" the dot moved to.

    Pistols used were:

    Glock 34 Gen 5 MOS Holosun 507c
    Glock 19 Gen 5 MOS Holosun 507c
    Sig Sauer P365X Holosun 407k

    I repeated this test for all three.

    So I'll cut to the chase.

    Basically, moving my eye to the Bottom, Left, or Right of the center had no effect, or at least the effect was so small as to be unnoticeable. The apparent location of the dot was invariant with left, right, or down movement of my eye.

    However, there was a consistent (all three) effect when I moved my eye to the top (T) of the sight window. The apparent position of the dot moved down by about 2". Meaning, for both my HS507c's, and one HS407K (red, 6 MOA dot) there does appear to be some parallax, consistently, if you move your eye upwards in the sight window, as in, up to 2". Out of interest, 2" at 25 yards would be about 8 MOA (8 MOA at 25 is 2.09, but ok).

    I'm no optical engineer, for sure, and I'm not quite sure what this means. But it was repeatable and consistent, with all three. I wonder if the curvature of the Holosun glass is different / not cast the same at the top of the glass?

    I'll have to think about this some more, but that's what happened.

    I was kind of gratified to see that if I kept my eye to a large circle, more or less within the eye point, there was absolutely no parallax I could see take place. It was just when I got to the top edge things started moving down.


    Edit to add: Theory: If you tend to look through the top part of the glass, and adjust POA so the dot "rests" on the target center, your rounds will land up to 8 MOA high.

    Interestingly here is a target I shot this past week, slow fire, at 25. The group was high. Maybe I was squinting through the top?

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    Same gun, same day, same ammo: The Test at 10 yards, within 10 seconds. Maybe this was through the center of the optic?

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    Or I just suck. I dunno.
    Last edited by RJ; 01-26-2022 at 02:41 PM.

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