Cowitness VS Lower 1/3 and Iron Sights, Which is Best?

Published on August 5, 2019
Duration: 14:54

This guide explains the differences between Absolute and Lower 1/3 cowitness setups for red dot sights, drawing on the expertise of the VSO Gun Channel host. It covers visual differences, physical considerations for shooter stature, the impact of height over bore on close-range ballistics, and practical considerations like sight clutter and emergency sighting methods. The host, demonstrating high authority with precision tools and detailed explanations, recommends Lower 1/3 for most users but highlights specific scenarios where Absolute might be advantageous.

Quick Summary

Lower 1/3 cowitness is generally preferred for red dot sights on AR-15s, offering a clearer optic window by placing iron sights at the bottom. Absolute cowitness aligns the red dot directly over the irons, useful for emergency sighting but potentially cluttering the view. Mount height affects close-range ballistics, causing point-of-impact shifts.

Chapters

  1. 00:00Introduction and Short Answer
  2. 01:18Visual Comparison: 1/3 vs. Absolute
  3. 01:53Equipment and Mount Critique
  4. 03:11Iron Sight Profiles and Fixed vs. Flip-up
  5. 05:15Height Over Bore and Ballistic Arc
  6. 06:07Range Testing: 10-Foot Deviation
  7. 08:27Recommendations for Absolute Cowitness
  8. 09:49The 'Ghost Ring' Trick

Frequently Asked Questions

What is the main difference between Absolute and Lower 1/3 cowitness for red dot sights?

Absolute cowitness aligns the red dot directly over the iron sight post, while Lower 1/3 cowitness places the iron sights in the bottom third of the optic's window, offering a clearer view. The choice impacts sight picture and height over bore.

Which cowitness setup is generally recommended for AR-15s?

The Lower 1/3 cowitness is generally recommended for most shooters on AR-15 platforms. It provides a cleaner sight picture by keeping the iron sights out of the primary red dot view, though Absolute cowitness has specific tactical advantages.

How does mount height affect shooting at close range?

A taller mount (like Lower 1/3) increases height over bore, which alters the bullet's trajectory at very close distances. This difference can cause a point-of-impact shift, as demonstrated by tests showing deviations of several inches at 10 feet.

Can the optic housing be used as a sight?

Yes, with an Absolute cowitness setup and a fixed front sight, the optic's housing can function as a large 'ghost ring' rear sight if the red dot fails and the rear iron sight is down. This is a valuable emergency sighting technique.

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