Finding the perfect sight picture is crucial for accurate and rapid target acquisition. For many handgun users, the concept of lower 1/3 cowitness (also sometimes called "lower third cowitness") provides an optimal balance between sight visibility and situational awareness. This guide will explore what lower 1/3 cowitness is, its advantages and disadvantages, and how to achieve it. We'll also examine how it differs from other cowitness styles and delve into factors you should consider when selecting the right setup for your firearm and shooting style.
Understanding Lower 1/3 Cowitness
Lower 1/3 cowitness refers to the relationship between your handgun's iron sights and your red dot sight (RDS). In this setup, the top edge of your iron sights is visible just below the bottom edge of the red dot window. This means approximately one-third of the iron sights remain visible below the RDS. This is different from absolute cowitness (where the iron sights are fully visible within the red dot window) and full cowitness (where the iron sights are entirely obscured).
Advantages of Lower 1/3 Cowitness
- Enhanced Situational Awareness: The visible iron sights provide a backup sighting system. If your RDS malfunctions (battery failure, etc.), you still have a reliable way to aim your weapon.
- Improved Sight Picture Acquisition: The visible iron sights help frame the red dot, making it quicker and easier to find the dot during aiming. This is especially beneficial in stressful situations.
- Reduced Eye Strain: The slight offset of the iron sights can reduce eye strain, particularly during extended shooting sessions or in low-light conditions. The visible iron sights act as a secondary reference point.
- Versatility: Lower 1/3 cowitness works well with a variety of RDS heights and iron sight configurations.
Disadvantages of Lower 1/3 Cowitness
- Slightly Higher Point of Impact: Due to the offset, the point of impact may be slightly different with the RDS versus using iron sights alone. This requires zeroing both systems independently.
- Potential for Obscured Sight Picture: Depending on your stance and how you hold the firearm, a portion of the iron sights might be partially obscured by the RDS. This might make for a slightly cluttered sight picture.
- Requires Precise Mounting: Accurate mounting of the RDS is crucial for achieving the proper lower 1/3 cowitness. Improper mounting can lead to an inaccurate and potentially dangerous sight picture.
Achieving Lower 1/3 Cowitness
Achieving proper lower 1/3 cowitness often involves selecting the correct RDS mounting height and potentially modifying your handgun's iron sights. Here's a breakdown of the process:
1. Choose the Right RDS Mount
The most important factor is the height of your RDS mount. Different manufacturers offer different heights, and choosing the wrong height will result in either absolute or full cowitness, or even no cowitness. Experimentation or careful research based on your specific handgun and RDS is critical. Many manufacturers provide specifications or online resources to aid in this selection.
2. Consider Iron Sight Height
Some handguns have taller sights specifically designed for cowitness setups. If your handgun's sights are too low, achieving lower 1/3 cowitness might be impossible without using an excessively tall mount, which can impact handling.
3. Zeroing Your Sights
Once you’ve achieved the desired cowitness, you need to independently zero your iron sights and your RDS. This ensures accuracy regardless of which sighting system you are using. You might find that the impact point differs slightly between both systems, necessitating adjustments.
Case Study: Glock 19 with Trijicon RMR
Let's consider a common scenario: A Glock 19 with a Trijicon RMR red dot sight. The stock Glock 19 sights are generally too low for a true lower 1/3 cowitness with an RMR. A taller aftermarket mount is necessary to achieve this setup. After installing the mount and properly zeroing the RMR and the sights, the shooter will benefit from the advantages of the lower 1/3 cowitness system.
Lower 1/3 Cowitness vs. Other Cowitness Styles
| Cowitness Style | Iron Sight Visibility | Advantages | Disadvantages |
|---|---|---|---|
| Lower 1/3 | Partially Visible | Backup sights, improved situational awareness, reduced eye strain | Slight point of impact difference, potential for partially obscured sights |
| Absolute Cowitness | Fully Visible within RDS window | Clear sight picture | Less situational awareness if RDS fails |
| Full Cowitness | Completely Obscured | Clean sight picture | No backup sights |
Conclusion: Making the Right Choice
Choosing the right cowitness style depends on individual needs and preferences. Lower 1/3 cowitness offers a compelling balance between backup sighting capability, improved situational awareness, and a relatively clean sight picture. However, careful consideration of the factors discussed above, including mount height, sight height, and zeroing, is essential for achieving a safe and effective setup. Always prioritize safety and practice regularly with your chosen setup to ensure you can consistently and accurately engage targets.