Co-Witnessing Iron Sights

[Riomouse911]

As I sat in the backyard tonight watching the original red dot co-witness with the top of my flagpole, I started thinking about red dots on AR rifles and pistols and wondered if there really is a need to "co-witness" the irons with the dot.

I have two AR's with dots that I think are "pretty close", but since I haven't specifically sighted the irons in with the dot I don't know for use how close they are to matching POI.

Is it important to you to co-witness irons with dot sights, or do you just set up the dot and forget it?

 

[1911 guy]

I have my own method. Not the only method. Not "The Method".

Dial in Iron sights. Install and dial in red dot sight for absolute co-witness.
I do not own any handguns with RDS, only rifles.

 

[herrwalther]

Yes. When the Army started issuing red dots with BUIS, We had to quickly get used to how to shoot with either. I learned marksmanship on iron sights so the red dot was the new thing on the block. The first red dots we had were terrible on battery life. So if we did not know how to setup iron sights correctly, you were essentially combat ineffective. Best case it fails during training or qualification. Worst case it happens when you really need it. The upgraded CompM4 sights had better everything. From battery life to durability. Even the battery compartment was in a more convenient location.

Now as a civilian stationed on FOB couch, old habits die hard. My AR build idea was to take the best parts of my service rifles for a private weapon. And I have the same model BUIS I used in the Army from 2006 on wards behind a red dot.

 

[Chuck R.]

I do similar, sight in BUIS first, dial RDS onto BUIS. Then I fine tune the RDS.

For my defensive set-ups I prefer a fixed front sight, so there's one less thing to worry about flipping. Due to that I prefer a lower 1/3rd co-witness rather than absolute.

I've yet to sight in an RDS that I co-witnessed off irons that was "perfect". Close, but not 100%.

Lower 3rd VS absolute:



The only issue, is remembering to use the lower 3rd of your optic tube if/when your RDS cuts out, but the tube can still be used as a giant "ghost ring".

 

[mdauben]

I put a co-witnessed red dot on my 1st gen S&W M&P Sport and I HATED it.

I found the sight picture cluttered, confusing and slow to aim. I literally could not use it with any facility. My next action was to get rid of the front iron sight.

 

[BigSteve57]

I've done this about a 1/2 dozen times as I've been slowly putting red dots on my firearms that could be used for hunting or for defense.
The reason is that my eyes can't see well up close anymore; seeing distance is no problem as I'm nearly 20/20.
If I'm shooting irons in a target/match situation I'll use special glasses that allow me to focus my dominant eye on the irons.

To the point...
As far as mounting red dots, I do a few things as there are different types of co-witnessing.
I have done 100% or absolute co-witness where the dot lines up exactly with the front & rear irons.
There is also lower 1/3 co-witnessing which some think is the best and I am a big fan of it as well.
This is where the irons occupy the lower 1/3 of the red dot's field and the red dot itself is in the center.
I've found that I pretty much can see the irons (the best that I can given my eyes) any which way I mounted the red dot; my mounts are all low or standard mounts..

All my red dots have quick detach so I can just pop them off if necessary.
I also do that so I can interchange red dots with scopes if I want to.
But if I remove the red dot and I don't have my shooting glasses I'm then kind of stuck!
Oh I'd do OK in a defensive situation to maybe 25 yards but that's it.

 

[Walkalong]

Very cool photo.

 

[Citadel99]

While in the Army? Yes. As a civilian? No. I just don't see the need for the way I shoot these days at the ranch or the range... Can always grab another battery and I'm not jumping out of airplanes and banging the rifle going in and out of humvees anymore so there is little chance of damage to the optic...

Mark

 

[Corpral_Agarn]

Good photo.

I usually sight in the flip up irons first, install the red dot, Sight it in.

I set the flip ups for absolute co witness but it is largely personal preference, IME.

 

[chicharrones]

I do similar, sight in BUIS first, dial RDS onto BUIS. Then I fine tune the RDS.

For my defensive set-ups I prefer a fixed front sight, so there's one less thing to worry about flipping. Due to that I prefer a lower 1/3rd co-witness rather than absolute.

I've yet to sight in an RDS that I co-witnessed off irons that was "perfect". Close, but not 100%.

Lower 3rd VS absolute:

View attachment 807576

The only issue, is remembering to use the lower 3rd of your optic tube if/when your RDS cuts out, but the tube can still be used as a giant "ghost ring".

That's what I have done. I prefer lower 1/3 as well so I can see through the red dot better.

 

[chicharrones]

Very cool photo.

Indeed.

 

[Riomouse911]

Very cool photo.

Every once in a while we get a really nice sunset. Since my house is up on a hill, I get to see it a bit easier than those who can’t see over the hills to the West. I’m glad I could share it with you.

Last evening was just one of those moments when everything lined up perfectly...the sunset, the flagpole topper, etc. This example of perfect alignment, sadly, doesn’t describe my shooting recently .

Stay safe!

 

[sota]

I'll be switching from absolute to lower 1/3rd co-witness, as I've determined that having the red dot low enough to make it absolute with the BUISs, makes my head/neck/cheek-weld/shoulder positioning uncomfortable. I guess I could add riser(s) to the BUISs, but I think that's getting a bit nutty.

@BigSteve57 have you considered moving the rear sight?



If you look you can see my rear BUIS is in front of the red dot. I did this because if I put it behind it becomes useless; it blurs out so much as to totally disappear. I spent some time doing some measuring and figured out I can put the rear sight at the same rough distance from my eyes as the rear sight on a pistol at full extension.

 

[GBExpat]

On my ARs that sport red dots, I am careful to assure that both BUIS and RDS are aligned.

My primary reason for doing this is to guarantee myself the same cheek weld.

 

[shoobe01]

Yes, but subtly less over time. This only for rifles as I am not yet an RDS-on-pistol guy.

My Meprolight M5s are all (I have 5) taller than usual for AR types, so are more like a bottom 1/4 cowitness. Makes a number of things nicer, but I quite like the view when I flip up the irons. They are truly backups. They work, but are absolutely not in the way if they pop up; one gun still has a fixed FSB, and it's there, but not in the line of sight unless I make it so.

 

[doubleh]

I use scopes, not red dots, on my rifles. My pistols that have red dots have no iron sights.

 

[Doc7]

@sota I guess my question is why should your head have to be uncomfortable to look through an absolute cowitness relative to a lower third? With an RDS you are focused on your target and by nature of the site there is no such thing as a parallax error with the red dot. With your neck at a normal position you should still see a red dot superimposed on your target. I recommend trying running your RDS with the black flip cover in place (so you aren’t trying to look through the red dot body with your right eye, if shooting right handed ) and giving it a try. You will find you don’t need to crane your neck down to the body of the sight.


@GBExpat this comment applies to you also. Your cheek weld does not matter with a red dot. There is no parallax error. This is the beauty of an rDS it can be used in all manner of awkward positions with no problem. Shoot a turkey with an unmounted shotgun for instance if ol Tom won’t let you move much without spooking.

 

[GBExpat]

@GBExpat this comment applies to you also. Your cheek weld does not matter with a red dot. There is no parallax error. ...

Thanks, but I am not trying to avoid a parallax error, just that my cheek(bone) is in exactly the same position whether using the RDS or BUIS.

 

[Doc7]

I don’t know why your cheek weld can’t be the same position regardless of witness location.

I am sure you already know this but I think it bears repeating for a future RDS user perusing this thread. If you flip the cap closed on the red dot, and shoot with both eyes open, you will still see a red dot on your target. You can do this with your cheek bone in the same weld position as when you use your iron sights. When you look and see your target, and your dot, and you shoot, you will realize that is just a fine and dandy cheek weld to use. After a while of getting used to it, open the cap back up. Now you can focus on your front sight for irons or your target for the RD. I don’t understand why you would need to adjust your weld for lower 1/3 or an absolute cowitness. It seems to me that you are trying to center the dot in the body of the sight, (only reason you would need to do this) as you would with a scope, and it’s just not the way an RDS is designed to be used. That’s why i recommend everyone shoot red dots with the black cover closed for a while to get used to the fact that you don’t need to see through the body of the sight at all for it to be usable.

 

[JeffG]

I use 45 degree offset BUIS. If my red dot fails, I cant 45 degrees to the right and keep going.

 

[GBExpat]

I don’t know why your cheek weld can’t be the same position regardless of witness location.

It is just the way that I like to do it, Doc7. I'm old, I'm allowed.

My preference has always been to shoot over irons. Even the (inexpensive) RDSs that I currently have on a couple of my ARs I consider to be more backup/lowlight than primary.

I bought my first RDS about 25 years ago. A short, 40mm, tube style. Interesting, but it did not capture my attention.

About 2000, or so, I bought a Bushnell HOLOsight (probably just prior to them becoming EOTech). That one, with its clear, focused 1MOA dot, I got used to using as a primary sight, no BUIS. Nice sight. I really liked the "no parallax" aspect. I used it on my first AR for ~15 years. It is currently back in its box for awhile.

With my two RDS ARs (16" carbines), I first sighted them in using the iron sights and then adjusted the RD to match the irons.

 

[wally]

I try to put co-witness BUIS on my guns with red dots whenever practical. Given my old eyeballs I generally end up adjusting the irons to match the dot after sight in. My main reason to have them is for a sanity check after rough handling. If they don't match I know something has been knocked katywumpus. They are also convenient to have as a reference point for adjustments when sighting in initially.

 

[BigSteve57]

I'll be switching from absolute to lower 1/3rd co-witness, as I've determined that having the red dot low enough to make it absolute with the BUISs, makes my head/neck/cheek-weld/shoulder positioning uncomfortable. I guess I could add riser(s) to the BUISs, but I think that's getting a bit nutty.

@BigSteve57 have you considered moving the rear sight?

If you look you can see my rear BUIS is in front of the red dot. I did this because if I put it behind it becomes useless; it blurs out so much as to totally disappear. I spent some time doing some measuring and figured out I can put the rear sight at the same rough distance from my eyes as the rear sight on a pistol at full extension.

As in moving the rear sight farther forward? The front sight is blurry without my special prescription glasses so I'm not sure it would help. But I can try. Easy enough.