All red dot sights exhibit parallax. I installed a FastFire 3 on the back receiver of my Garand and the parallax made it unsatisfactory for use beyond 50 yards. Suffice to say, the FastFire 3 is no longer on that rifle.


Green Eyed Tactical did a comparison test of the parallax in many different red dot sights. Their exhaustive and scientific report can be down loaded here: https://www.greeneyetactical.c...-dot-sight-parallax/

However, for simplicity, here is an extract of part of the report Summary:

quote:

One of the most significant aspects of the test is the comparison of the observed results, compared to the specific manufacturer’s claims as to the parallax characteristics of the optics. It should be noted that it is not made clear what aspect of parallax the manufacturer refers to in their product data. As parallax is defined as the apparent change of position of an object, viewed upon two different angles— it could refer to (in the case of this test) as to red dot movement or the actual target (viewing area) movement:

Aimpoint claims that the T-1 is a “1X (non-magnifying) parallax free optic” (Aimpoint, 2017), while the overall results showed an average deviation of 9.678492518 MOA from all distances and tests.

Aimpoint claims that the T-2 is a “1X (non-magnifying) parallax free optic” (Aimpoint, 2017), however, the average deviation observed across all distances and tests was 4.5 MOA.

Aimpoint claims that the Comp M2 is “Absence of parallax — No centering required” (Aimpoint, 2017), however, the average deviation observed across all distances and tests was 6.289849283 MOA.

Aimpoint lists no parallax claims on their website, that could be found at the time of publication, about the Comp M4 or the PRO.

Vortex claims that the StrikeFire II is “Parallax Free” (Vortex Optics, 2017), however, the average deviation observed across all distances and tests was 7.702254543 MOA.

Vortex claims that the Razor is “Parallax free” (Vortex Optics, 2017), however, the average deviation observed across all distances and tests was 15.59702284 MOA.

Trijicon claims the SRS is “PARALLAX-FREE” (Trijicon, 2017), however, the average deviation observed across all distances and tests was 16.26182102 MOA.

Trijicon claims the MRO is “PARALLAX-FREE” (Trijicon, 2017), however, the average deviation observed across all distances and tests was 13.37388861 MOA.

Leopold claims “The Leupold Carbine Optic (LCO) is parallax free” in an answer to the product questions (Service, 2017), however the average deviation observed across all distances and tests was 12.86041119 MOA.

EOTech claims that their optic is subject to parallax error of up to 14 MOA (EoTech, 2017). This claim is made generally on their FAQ page, without being model specific, however, the averages of the models tested across all distances and tests were: 1.658588792 MOA for the EXPS 3.2, 1.723615393 MOA for the EXPS 3.0, and 3.400581317 for the 516.

Burris claims that the Fast Fire 3 is “parallax free” (Burris Optics, 2017), however, users noted an average of 4.024137943 MOA of movement.

At the time of this testing, we could find no public claims by Primary Arms as to the parallax characteristics of the optic tested.

As we can see, there is a wide variance in what is claimed by the manufacturers and what is observed. All but Eotech, who over estimated error, failed to produce results that match the claims.

That stuff is a bit of a worry, Grenadier.

While they're not my bag, I'd always assumed being parallax-free was the central property of those things - otherwise they're just reflected lights pretending to be sights and the only way to make them work is with a stock giving perfectly consistent head position.

Naive me, I have always assumed the 1x devices would have negligible parallax. It looks to me like Green Eyed Tactical's computer can generate far more decimal places than their measurements are capable of producing??
C.G.B.

looks to be
more like human interface variance rather than device

quote:

Originally posted by DuggaBoye:
looks to be
more like human interface variance rather than device

Well, if you got into a good shooting position and clamped and screwed your head into place so your eye position would never change then you could eliminate "human interface variance". Short of that you will find your eye varies from exact dead center to some degree every time you mount the rifle, alter your position, or raise and lower your head. "Human interface variance" is probably greater for red dot sights mounted on handguns.

Red dot sights are designed for short range use. Even 4 MOA and 8 MOA maximum parallax values equate to only 1" and 2" variance at 25 yards, respectively. That's suitable for urban environments. But when people install red dots on hunting rifles they intend to use for 100 yard and longer shots they're greatly limiting accuracy.

quote:

Originally posted by cgbach:
Naive me, I have always assumed the 1x devices would have negligible parallax. It looks to me like Green Eyed Tactical's computer can generate far more decimal places than their measurements are capable of producing??
C.G.B.

My computer does even better. It says the average of 1",2", and 4" MOA is 2.3333333333333333333333333333333333333333333333" MOA

... repeating


Grenadier is right, and the places in the averages are probably correct, if you can be bothered taking them that far.

On that list of sights Burris is the only small one. The rest are semi-tube or large tombstones.

Only the EOT's were better (than burris) as far as parallex.

Good point, richj, and while 2 or 4MoA parallax would be a fair bit in a normal scope, the Burris is indeed better than most of the others.

In fact I think the article is slightly misleading in the list of the sights tested above the colored tables. Because the brand that performed best was at the top of the list, it gives the impression that the numbers on the right indicated the parallax. In fact they are just the ID numbers, or the order listed, something that could have been deleted for clarity.