Zeroing your red dot using iron sights—often called co-witnessing—is a reliable way to align your optics, especially if you're setting up a new sight or have no access to a range. Here’s a quick guide on how to zero a red dot with iron sights:
Start by securely mounting both your red dot sight and iron sights on your firearm. Decide if you want absolute co-witness (red dot aligned exactly with the irons) or lower 1/3 co-witness (dot sits slightly above the irons in the optic window).
With the firearm on a stable surface, look through your iron sights and adjust the red dot (using windage and elevation dials) until it rests perfectly on the front sight post. Make sure the rear and front sights are aligned as usual.
Once your red dot is visually aligned with the iron sights, head to the range to fine-tune the zero. Shoot a few groups at your desired zero distance (commonly 25 or 50 yards), then make small adjustments to the red dot as needed.
Zeroing your red dot to match your irons is a smart backup strategy—if your optic ever fails, your iron sights will still keep you on target.