Co-witnessing is an essential setup technique for AR-15 shooters who want a reliable backup sighting system in case their optic fails. By aligning a red dot sight with iron sights, shooters can ensure consistent accuracy and a seamless transition between sighting systems. This guide will walk you through setting up co-witness sights, whether you're using a red dot sight, holographic sight, or scope. We’ll cover absolute vs. lower 1/3 co-witness, mounting considerations, and zeroing techniques to optimize accuracy.

What Is Co-Witnessing on an AR-15?

Co-witnessing means aligning your red dot sight with your backup iron sights (BUIS), so they work together. This allows for redundancy if the optic loses power, fogs up, or is damaged. There are two primary types:

1. Absolute Co-Witness

In absolute co-witness, the red dot aligns perfectly with the iron sights. This setup ensures that when you aim, the red dot sits directly on top of the front sight post.

2. Lower 1/3 Co-Witness

In a lower 1/3 co-witness, the red dot appears slightly above the iron sights in the optic’s window. This provides a clearer field of view without obstruction from the iron sights.

Step-by-Step Guide: How to Set Up Co-Witness Sights

Step 1: Choose the Right Optic and Mount

Select a red dot sight or holographic sight that supports co-witnessing. The mount height determines whether you achieve absolute or lower 1/3 co-witness.

Recommended Mount Heights for Co-Witnessing:

 Step 2: Mount the Optic

• Secure the optic on the Picatinny or Weaver rail.
• Ensure the optic is mounted tightly to prevent movement.
• Adjust the position for a comfortable sight picture.

Step 3: Install Backup Iron Sights

• If using flip-up sights, make sure they clear the optic’s field of view when folded down.
• If using fixed sights, ensure they align correctly with the optic.

Step 4: Align and Zero the Sights

Adjust windage and elevation so that the red dot sits directly on or slightly above the front sight post, depending on your chosen co-witness type.

• Align the iron sights with the optic reticle.
• Set your zero distance (25, 36, or 50 yards, depending on preference).
• Adjust the red dot’s windage and elevation until it sits perfectly on the front sight post (absolute) or slightly above it (lower 1/3).
• Test at different distances to confirm alignment.
  

Step 5: Confirm Co-Witness with Live Fire

Take a few test shots to ensure the alignment remains intact. If necessary, make final micro-adjustments to perfect co-witness accuracy.

The Final Ramble

Setting up co-witness sights on your AR-15 is a valuable skill for improving accuracy and ensuring a reliable backup aiming system. Whether you choose absolute or lower 1/3 co-witness, follow the setup process carefully, zero your sights properly, and test with live fire.

Would you like recommendations on the best optics for co-witnessing? Let us know in the comments!