Comparative Study of Red Dot Sight Parallax

[NH Shooter]

Not sure if this has been posted here before, but here's the link;

https://www.greeneyetactical.com/201...ight-parallax/

Cliff Notes Version

Red Dot Sights have been promoted as "parallax free" by just about every RDS manufacturer. The big deal about this is the idea that as long as you place the dot on the target, it makes no difference where the dot appears in the optic. As long as you can see the dot somewhere in the optic and place it on the target, you're good to go. It turns out that this claim is largely buffalo bagels.

As someone who enjoys good gun porn (many really excellent photogs out there), I've noticed a trend of rifles equipped with a RDS also sporting a fixed front sight post, mostly in combination with a folding rear. It wasn't until I read the study (link above) that it made sense, confirmed by comments on this topic on MC4: using the front sight post to achieve repeatable dot location in the field of view for maximum accuracy by minimizing the hellacious parallax some well known, top-tier brands of RDS suffer from.

Maybe I'm out-of-touch with the current carbine sighting-system group-think, but I certainly feel better informed now. I also don't feel as bad now running irons only. :-)

[MistWolf]

When I first got my Aimpoint H1, I tested it for parallax and discovered there was quite a bit. I found that if you keep the dot centered, front sight or no sights, it still gives good precision. Good shooting form still applies.

[Default.mp3]

I know both the study and its author have been called out. While no optic is truly parallax free, is it really as bad as claimed by the paper? I'm not totally convinced, but I've no dog in the fight (I use a magnifier to force a consistent position, given how tight the eyebox is on the G33). I've read the paper, and not found any glaring issues with the methodology, though I've also admittedly little experience with creating scientific studies, nor is my understanding of optics that in-depth.

Another article about parallax with RDSes, although the most educational parts, the videos, seem to be dead: http://www.breachbangclear.com/parallax-free-isnt/

@Wayne Dobbs

[NH Shooter]

My own observation through the use of several Aimpoints is that I could never hold the same level of precision as I could with irons on an AR. I attributed this to my astigmatism and came to accept what I could do (and couldn't do) with a RDS. My dabbling in NRA High Power decades ago with a M1A re-enforced my thinking that I simply could shoot with greater precision with a good set of irons. For me that remains a given.

Having just found this study a few days ago and reading the comments on it was timely for me as once again I have been thinking of getting a RDS to compliment the DD fixed sights on my carbine. One of the major perceived benefits for me was the idea of not needing perfect eye/head alignment to make the shot. It now seems that theory is largely debunked, leaving the only other RDS benefits as (1) acquiring a close-range target perhaps a bit quicker and (2) being able to establish aim in low light conditions. Add to that the reality that I can shoot more precisely with irons and that the RDS offers no advantage in target identification, along with cost, increase in bulk and weight and because they now have to be co-witnessed through an optic that could become obscured with dirt or water - compromise the utility of the irons - leaves me feeling that for my use a RDS is perhaps as much a liability as it is an asset.

I've also tried three mid-tier LPV scopes over the years: a SWFA 1-4X HD, a Bushnell 1-4X Elite and most recently, a Leupold VX-R Patrol. While I liked the lighter weight VX-R the best, even in a relatively lightweight mount it added over a pound of weight to my "lightweight" carbine, and of course all of that weight is above the bore axis. Maybe it's the old High Power experience coming out in me, but I always found that much additional weight so high up compromised the handling of a carbine. While precision and target ID is certainly enhanced, it's at the expense of everything else...not to mention the absurd amount of $$ that can be dropped on a good optic set up.

So here I am back to recognizing that a good set of irons has thus far proven to be the best compromise for my carbine needs. As much as I try to find a way to spend more money on an yet another AR optic package, I remain unable to justify the cost (and weight)-to-benefit ratio.

Maybe I'll just save the money for more pistol stuff. :-)

[jellydonut]

I know a lot of people are coming out saying that this is something 'everyone' knew, but I sure didn't before Eric blew the covers open for me. Every single red dot manufacturer has been claiming parallax-free in their marketing, literally for decades.

What I do know is that it's a lot easier to be centered behind my Razor that has an actual reticle, than it is to center a free-floating dot in a red dot sight. If there's all of a sudden a need to do this, then an LPVO is simply the superior option in more ways than previously.

[NH Shooter]

What I do know is that it's a lot easier to be centered behind my Razor that has an actual reticle, than it is to center a free-floating dot in a red dot sight. If there's all of a sudden a need to do this, then an LPVO is simply the superior option in more ways than previously.

Yup, as long as the weight and bulk doesn't get you down.

IMO, here are the desired strengths of an AR optics package;

1. target acquisition speed
2. eye box/head placement flexibility
3. precision potential
4. clarity/sharpness of reticle/aiming point
5. visibility of reticle in low light
6. target identification potential
7. the above vs. weight/bulk/cost penalty

The strong points of a RDS seem to be 1, 2 and 5 with the least penalty on point 7.

The strong points of the LPV seem to be 3, 4, 5 and 6 with the greatest penalty on point 7.

So it seems the RDS rule the CQC role while LPVs prevail in longer range engagement. No surprises there, as is the point that a RDS can be pressed into longer range engagement with some measure of success just as the LPV can be pressed into the CQC with some measure of success.

Here's another optic package that certainly isn't mainstream but has some interesting potential;

Leupold FX-II 2.5x20mm Ultra-Light Rifle Scope

Aero Precision Ultralight 1" Scope Mount, SPR

Here are the boxes I would check for this package;

1 - only because of the extremely forgiving eye box and long eye relief of this scope.
2 - comparable to a RDS when minimizing parallax is a concern
3 - 1 MOA center reticle hair superior to RDS
4 - adjustable diopter to render sharp reticle, not sensitive to astigmatism
6 - magnified optic, certainly superior to RDS or irons
7 - low cost (under $400), low weight (9.7 ounces) = much lower penalty than typical LPV

The only real downside is a non-illuminated reticle but considering all of the benefits, one might be able to overlook that.

I'm seeing if I can talk myself into trying out this set up.

[Chris17404]

In this recent video by Aaron Cowen of Sage Dynamics, he discusses the insignificant nature of parallax issues related to LPV optics and (to me) reaches the conclusion that you definitely do not need to have your eye perfectly centered behind a LPV reticle to get solid hits on target at long self-defense distances. One more data point that suggests the RDS has little real benefit over a LPV?

https://www.youtube.com/watch?v=2s4aiUHhG3c

And here is his take on RDS parallax:

https://www.youtube.com/watch?v=TUBcewtUBpQ

[vmi-mo]

When I look at a gun that will be used in combat, I try like to hell to limit the mechanical stuff that I will need to overcome to make hits. The fewer things that I have to keep in mind, focus on correcting, or be cognizant of, the better. This means I can devote more CPU to the situation and not too shooting.

My issue with most RDS (sans the EO) is that I can have a head position that induces parallax and It is not as readily apparent to me. Meaning I have to, in my engagement cycle, remember "is my head position good and is parallax mitigated"... That sucks. When using LVPO, because scope shadow is much more readily apparent, I am immediately aware, my sight picture is jacked. Long gunners, because they deal with this on an entirely different level usually remind each other "check parallax"

Also, clean firing positions are a great white buffalo in reality. Walls always seem too short, too high, corners too jagged, rocks too slanted etc. All these things lend themselves to awkward head positions.

Finally, man sized target??? WTF is that?

[OlongJohnson]

I have an H1 on the 1301, as the scatter is workable for buck, but prefer an etched reticle with my astigmatism.

Have a couple of these: http://www.vortexoptics.com/product/...rt-moa-reticle

Would be interesting to evaluate the parallax with it.

[Wayne Dobbs]

My own observation through the use of several Aimpoints is that I could never hold the same level of precision as I could with irons on an AR. I attributed this to my astigmatism and came to accept what I could do (and couldn't do) with a RDS. My dabbling in NRA High Power decades ago with a M1A re-enforced my thinking that I simply could shoot with greater precision with a good set of irons. For me that remains a given.

Having just found this study a few days ago and reading the comments on it was timely for me as once again I have been thinking of getting a RDS to compliment the DD fixed sights on my carbine. One of the major perceived benefits for me was the idea of not needing perfect eye/head alignment to make the shot. It now seems that theory is largely debunked, leaving the only other RDS benefits as (1) acquiring a close-range target perhaps a bit quicker and (2) being able to establish aim in low light conditions. Add to that the reality that I can shoot more precisely with irons and that the RDS offers no advantage in target identification, along with cost, increase in bulk and weight and because they now have to be co-witnessed through an optic that could become obscured with dirt or water - compromise the utility of the irons - leaves me feeling that for my use a RDS is perhaps as much a liability as it is an asset.

I've also tried three mid-tier LPV scopes over the years: a SWFA 1-4X HD, a Bushnell 1-4X Elite and most recently, a Leupold VX-R Patrol. While I liked the lighter weight VX-R the best, even in a relatively lightweight mount it added over a pound of weight to my "lightweight" carbine, and of course all of that weight is above the bore axis. Maybe it's the old High Power experience coming out in me, but I always found that much additional weight so high up compromised the handling of a carbine. While precision and target ID is certainly enhanced, it's at the expense of everything else...not to mention the absurd amount of $$ that can be dropped on a good optic set up.

So here I am back to recognizing that a good set of irons has thus far proven to be the best compromise for my carbine needs. As much as I try to find a way to spend more money on an yet another AR optic package, I remain unable to justify the cost (and weight)-to-benefit ratio.

Maybe I'll just save the money for more pistol stuff. :-)

Red dot sights on carbines used in extremis aren't about super tight groups, but about accurate shots delivered at speeds that iron sights can't approach. If you can shoot tighter groups with iron sights, that's cool, but that application has little to do with actual street use of the patrol rifle. No optic is parallax free, but many are practically so unaffected by parallax in field use that they get labeled so. I know that I've watched enough asymmetric positional shooting of carbines to 200 yards and the attendant hits using RDS units (both Aimpoint and that EOSomething sight) that it was clear parallax wasn't a game changer in any way. By the way, virtually NONE of those shots could've been made with iron sight systems. We have the technical axle we can wrap around or we can go shoot the fuck out of a bad guy in sorry conditions. Quality RDS units make that possible.

I've been a serious rifle shooter for lots of years and while I can do decent work with the GI irons, I've never been able to shoot tighter groups with them than I can a red dot sighting system and neither could the thousands of shooters I've watched with both.