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Peep Sight vs Open Sight: A Tale of Two Radii

Peep Sight vs Open Sight: A Tale of Two Radii

SIGHT RADIUS! MAH IRONS! Sight radius has been a mainstay argument for 20 inch AR15s for a long, long time. Another common argument is comparing the sight radius of western peep sights v.s. open sights such as those found on the AK platform. While we may have made sight radius and irons sights redundant with red dots and magnification, it’s still a tool in the toolbox I always want to explore. Let’s take two largely identical guns, and compare performance with the same platform. One equipped with leaf sights, the other peep. How much do sights and sight radius matter?

Enter Ruger 10/22:

The Ruger’s I am shooting today have two big differences: the stock and the sights. Otherwise, the trigger, barrel, and other internal mechanisms are the same as delivered from Ruger sans 20 years. With these two fairly identical rifles, I feel it will be a valid comparison between the open sights, and long sight radius peep. I set up a simple test done at 50 yards and shot from a prone supported position. I did my best to aim small, miss small. Both rifles shot the same ammo.

Sights Compared:

Top: Ruger 10/22 x Samson Sight Package. Bottom: Factory Ruger 10/22 with factory sights. The BX-15 magazine was used between both rifles and was perfect for prone shooting.

The open sights of the factory Ruger are familiar to most shooters who have handled one. The notch and gold bead are just another variation of open sights which attempts to aid in alignment with contrast and placement. The Achilles heel of such systems is that the eye can only focus on one focal point. Everything before or after that point will be out of focus. When attempting to align three components, the target, front sight, and rear… precision is impacted by the fuzzy outline of the rear sight and the target. Remember the front sight is our focal point. Precisely aligning an in-focus orb into an out-of-focus notch can only be done with so much precision.

In theory, this is what you are seeing when lining up the Ruger open sights. Image From: https://www.riflemanschallenge.com/aiming.html

In practice, this is what you actually get: Clear front sight, fuzzy rear, fuzzy target.

In contrast, the peep sights operate on a different mechanism. Since we are looking through the rear sight, which is a pinhole, it improves our ability to focus on things both near and far. Focusing on the front sight becomes easier, and the target remains sharper due to the enhancement of our depth of field. For those without a reference, a simple experiment can be done with an index card and a pinhole poked through it. Extend your finger pointing up as a “front sight” and focus on the tip of your finger. Try and keep it in focus while reading the spine of a book across the room. Now bring up a pinhole poked into an index card in front of your eye and do the same thing. The book spines are much easier to read while focusing on your “front sight”. When there is adequate light, peep sights are superior simply because they give our ability to focus on the front sight AND the target a boost. Remember when you peer through the rear peep, its job is done. Ignore it. Front sight crystal clear, target aligned. Squeeze.

Peep sights let you focus on the front sight and improve the ability to clearly see the target. This improves as the peephole becomes smaller and smaller… at the cost of light.

Results:

I went out on a bright sunny day with no wind. I shot a generic Remmington .22LR load that was over 10 years old. Both rifles shot the same load. Objective results were as expected. A 1.87 MOA reduction in group size was seen by using peep sights vs the open sight. Overall, the verticle dispersion is much less with peeps whereas open sights had more severe vertical dispersion and slightly wider horizontal dispersion.

Peep Sights with a long sight radius showed a group size of 2.05 inches / 3.92 MOA.

The factory Ruger open sights revealed a 3.03 inch / 5.79 MOA group. Note the verticle dispersion.

It was as expected. Peep sights with their longer sight radius and ability to enhance your focus resulted in a more consistent grouping. The little 10/22 with generic fodder was accurate enough to gauge the difference between sight and shooter performance. It was refreshing to get behind a .22LR again after not having a plinker for many years. The Samson Sight Set was awesome to use, and expect a full review of the setup shortly. Need some parts for your 10/22? Support the site and visit Brownells.com for tons of 10/22 components. Can’t find a 10/22 in stock? PSA has you covered. 

Lothaen Out!

Written by lothaen

2 Comments

  1. HRB · April 14, 2021

    The distance between front and rear primarily affects graduation. Between front sight and eye affects focus. Between rear aperture and eye affects depth of field as you’ve shown. A better test of “radius” would be shorter and longer open sights, or shorter and longer apertured sights. Hmm, an AK versus an M4 with the aperture ground to a notch…

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