Home How To`s How To Properly Co-Witness Optic With Iron Sight

How To Properly Co-Witness Optic With Iron Sight


red dot co-witnessing with iron sight

Co-Witnessing is the ability to use your iron sights in coordination with a red dot or a holographic optic. The point of co-witnessing is to allow users a BUIS, also known as back up iron sights.

Anytime you attach electronics to your rifle you run the risk of them failing, and anytime you run an optic on your weapon you run the risk of it failing. An optic that relies on electronics to function can be a devastating loss in a combat, self defense, hunting, or competition should the optic fail.

It’s critical to know how to co-witness when you are running an electronic, non magnified optic. If you have a proper co witness sight you can transition seamlessly from your optic to your back up iron sights. This allows shooter to continue with their chosen objective with hardly a second lost. Another advantage is the ability to use iron sights to make precise shots at close range. Iron sights, well good iron sights, are going to be more accurate and more precise when used appropriately.

You can also use iron sights to avoid running into parallax with your red dot or holographic sight. Parallax isn’t a huge concern if you are engaging large targets, like man sized targets. For small targets, like shotgun hulls, parallax can have an effect, iron sights do not suffer from parallax.

3 Simple Steps To Follow

1. The first step is to actually have iron sights. Way too many rifles these days are coming from the factory in a sight free configuration, this isn’t just cheaper, or budget minded ARs, but my SIG 556R came without irons. So have iron sights.

Most optics, or the ones we recommend in our buying guide, are designed to co witness with AR 15 height sights, and since this is the most popular rifle in the United States, this is probably the rifle you have. On a standard A4/A3 upper a fixed front sight and a standard height rear sight like those from Magpul or Yankee Hill will align with nearly every red dot and holographic sight on the market. If you use non standard iron sights or an optic that doesn’t co witness you’ll need a riser or spacer.

Many optics will also have the option of a rise or spacer to raise your sights to AR sight levels, or lower then to co witness with other rifles. For example my Aimpoint T1 can co witness with my AK sights in its stock configuration. For different rifles you’ll have to experiment with the height of your sights, and the height of your optic.

2. Once you have the iron sights, optic, and the spacer/riser if necessary you’ll move to zeroing your iron sights. Iron sights should be zeroed first. Once you zero your iron sights and you have confirmed and are comfortable with their zero you can mount your optic.

3. Once the optic is mounted you’ll need to adjust the reticle until it is in line with your iron sights.

You’ll need to behind your rifle looking down the sights to align the dot with the iron. This is where a bipod, sandbags or a lead sled can come in handy. Once the sight is aligned you need to confirm the zero with just the optic. This means you need to replicate the same shooting position, shoot style, range, and ammunition you used for your iron sight zero. The reticle on your red dot or holographic optic should match your iron sights.

That Is All Folks

So preparing your weapon and optic to run in coordination with iron sights is rather easy. The importance is that it is done correctly. You’ll be depending on your iron sights and there is no reason to remove them, so leave them in place. You’re now set up to co witness with your iron sights. It’s important to maintain your skills with iron sights, so practice with irons occasionally, and maintain your skills. Co-witnessing doesn’t matter if you can’t shoot with iron sights.




  1. Interesting article. As many opinions out there as authors, and most all of them hopelessly misguided. What I’ve offered to try and enable understanding regarding co-witness with optics is asking them how they’ll use their weapon when they can no longer see through them. Dirt, breakage, battery dies, or simply dont have time to pop the lense caps – or in their panic forget to take them off.
    There are zillions of posted questions online about concerns regarding front sight posts potentially obscuring the field of view through ACOGs or red dots, and none asking how they’ll use their front sight when they can’t see through their ACOG.
    I’ve got a Sig PM400 SWAT w/ 11.5″ barrel, w/ Sig brace and front sight post on the other end. As typical, its got a short-pull trigger job, Robar inner coating and Cerakote outside. It’s great for close to medium range targets. On this Sig is my Trijicon TA45 ACOG (yellow triangle) which has a tube cast into its underside for a reason. It’s to see through to the front sight pin while using my Magpul BUIS rear sight (whether on a carry handle or pop-up rear BUIS) – absent the benefit of the magnified optics with the cool science experiment at work within. Even LaRue doesn’t get it. Their fantastic mount, the only unit for the TA45, is set at just the right height to look through the optic at the front sight post height – not the co-witness height. Mounting the Trijicon/LaRue assy on a 3/4″ picatinny riser puts it right where you want for co-witness use though.
    Now, I’ve got another Sig PM400 w/ Law Tactical folder and Phase 5 pistol buffer tube,, but w/ a 7″ barrel behind a Sanders 2pc flash can (whole thing folds up to fit in a typical laptop bag). This is a CQB tool. Being so, very rapid target acquisition is Step 1 or there’s no Step 2. I’ve found my Sig Romeo 5 w/ standard hi-rise mount to be optimal for me and my purposes. No magnification, but excellent field of view, activation on motion red dot (also sleeps w/ no motion; battery lasts forever). Projected lasers are great if you are hip-shooting, or for bad guys in the dark to know where you are – exactly (and flashlights are bullet magnets, duh). The height of the Romeo 5 is exactly at the height of my BUIS’s. If I’m using them, the red dot in the center of my rear sight is acting as a front sight pin would at the range, during the day. If that red dot happens to fail, the BUIS front pin is still out there. If it’s smashed, either it’s coming right off, or I just keep pointing the tool at the target and working to eliminate the threat (perhaps as I back out of the room).
    Shot of realism: Most people never consider how quickly they’ll be blinded in a dark room just after the first shot goes off. Sights and optics rely first on the guy holding the gun actually having functional vision. Nobody’s chatting about how to ensure that – esp. with all their commentary about optics that work with both eyes open and forward.