Background
In the early days of red dot optics, co-witnessing referred only to rifles. At that time, durability and battery life were primary concerns for red dots, so iron sights were often aligned through the optic window to be used as a backup sighting system in case the dot failed. It was a fast and easy transition from the dot to the iron sight since they were all in the same sight picture. There were two main co-witnessing heights: absolute and lower third.
Lower Third: The lower third co-witness addresses the sight picture problem by having the front sight in only the lower third of the window. Red dots are mounted at usually 1.57 inches from the top of the rail to achieve this co-witness.
Today, things have evolved. Let’s look at co-witnessing in both the rifle optics and pistol optics worlds.
Rifle Optics
There has been a trend in rifle optics toward using higher and higher mounts. This was initially done when aiming lasers and night vision began to see widespread use. IR aiming lasers mounted at the front of the gun would obscure red dots at an absolute or lower third co-witness height.
That’s partially why taller mounts became popular. A 1.93-inch mount had enough height to clear a laser. As an added benefit, this keeps the shooter’s head in a more natural, upright position, as opposed to scrunched down for a lower optic height. It also allowed easier aiming when wearing night vision or gas masks, because shooters no longer needed to lower their heads behind the optic.
Now, 2.26-inch and higher mounts are not uncommon. The problem with these taller mounts is they preclude co-witnessing because the optics are so much higher than traditional iron sights.
Alternatives
There are four popular alternatives. First, because the mounts have become so high, it is now possible to look through the base of the mounts to see the iron sights. These mounts now have skeletonized bases to allow this method.
Secondly, backup sights can be offset at 35 or 45 degrees from vertical, so the shooter can simply roll the rifle over to see either the backup irons or another red dot. This has become popular in the competitive shooting world, like 3-Gun. Competitors will have a low-power variable optic mounted on top as their primary scope with an offset red dot. Long-distance targets will be engaged with the primary, while shorter-range targets can be hit with the offset red dot.
Collapsible iron sights are another alternative, with the primary optic mounted on quick-detach mounts. If the primary optics goes down, it is removed, and the backup irons sights are deployed.
The final option is simply to do away with the iron sights. Co-witnessing for rifle sights has almost become outdated. If the point is to have a backup sighting system, the offset or the aiming laser can do the same job.
Pistol Optics
Co-witnessing has found a new home with pistol red dots. Just like in the early days of rifle red dot sights, pistol optics still have skeptics. Battery life and durability are still in question, so many shooters insist on having co-witnessed iron sights.
Because the technology of mounting red dots to pistols is still in its early stages, there is no one solution to co-witnessing pistol iron sights. It all depends on the specific pistol and how it works with a particular red dot. Some pistol platforms and optics have it easier than others, and it is not always possible to get an absolute co-witness.
Related: Why Pistol Red Dots Are Awesome – Top 5 Benefits
Normally, most iron sights show up in the bottom third or fourth of the optic window. With some pistol and red dot combinations, the iron sights barely will be visible in the window. Sometimes, extremely tall front sights are necessary to get a co-witness.
Rear Sight
In addition, there are many options for the placement of the rear sight. Some pistols have the rear sight mounted on the slide, while others include the rear sight on the optic plate system.
Some co-witness options mount the rear sight behind the optic, and a few have it in front of the red dot. Certain red dots have integrated rear sights, and finally, some systems have completely done away with iron sights because red dots are so reliable. This is more prevalent in the competition world.
Conclusion
Ultimately, only you can tell if co-witnessing is right for you. It all depends on your use case and how much redundancy you require.
