If you have used a red dot sight, you might already know that red dot sights sometimes fail due to extreme environments or accidents. Therefore, if both the iron sight and red dot sight are used while shooting, the iron sights can be a backup plan when the red dot sight fails.
So today we are going to talk about what is absolute co-witness height? What does lower 1/3 co-witness mean? And how to choose a co-witness red dot for your firearm?
Note: This article will introduce the pros and cons of absolute co-witness height and lower 1/3 co-witness height. After reading it, you can know how to choose and install co-witness sights for your firearm.
What Is A Co-witness Sight?
Co-witness sights refer to a relationship between your optical sight and iron sight. The two sights work together as “co-witness sights”.
Absolute Co-witness and Lower 1/3 Co-witness Meaning
First of all, absolute co-witness and lower 1/3 co-witness are just different installation methods. The height of your red dot sight (the amount of iron sight that occupies the sight picture of your red dot) is the biggest difference between them, so, there is nothing good or bad about them, just choose a proper one according to your shooting preferences.
There are 3 popular center heights, as picture 0 shows, the absolute co-witness height is 36mm (1.4 inches); the lower 1/3 co-witness height is 40.4mm (1.6 inches); the other one is 38.1mm(1.5 inches).
If you still feel confused, picture 1 will show you what absolute co-witness and lower 1/3 co-witness look like, thus clearer for you to understand. If you mount the red dot sight in the way that the center dot coincides with the iron sight in the middle, this is called absolute co-witness or 100% co-witness. If you mount the red dot sight higher than the iron sight, and the iron sight appears in the lower 1/3 of the optic window, it is called Lower 1/3 co-witness. You need to change your line of sight to make the red dot align with the iron sights.
Absolute Co-witness Height or Lower 1/3 Co-witness Height, How to Choose?
Two different heights, which is better for you? Let’s take AR 15 as an example. For an AR 15 with a fixed iron sight, you’d better go with lower 1/3 co-witness for its better visibility. However, for an AR 15 with a flip-up iron sight, absolute co-witness is a good choice for convenience.
Pros and cons of absolute co-witness and lower 1/3 co-witness
Using Absolute co-witness, the red dot is always aligned with an iron sight so you can react faster and more accurately when the target appears in your field of view, but the iron sight will block part of the field of view.
Using Lower 1/3 co-witness can provide a wider field of view and less interference, but you need to change the line of sight when you need both red dot sight and iron sight.
Summary
| Absolute co-witness | Lower 1/3 co-witness |
| Pros:
1. Shooters can react faster 2. More accurate Cons: The iron sight will block part of the field of view |
Pros:
1. Wider field of view 2. Less interference Cons： You need to change the line of sight to coincide the red dot with the iron sight |
Therefore, the best advice is to try them both, then make a choice between absolute co-witness and lower 1/3 co-witness according to your personal tastes and habits. Check Victoptics SRD 1×20 Reflex Sight to set up your co-witness settings.
Install and Adjust Co-witness Sights
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