When people start looking to purchase a new hand gun one of the considerations they look at is the sight radius, because “longer sight radius’s make the gun more accurate.”

This isn’t actually true, a longer sight radius just makes the gun easier to shoot accurately. Let’s take a look at that…

What is sight radius?

The sight radius is the distance from the face of the front sight to the blade of the rear sight (the parts you are looking at when you are shooting). Typically this is a function of how long the slide is and therefore shorter guns like the Glock 26 have a shorter sight radius than a Glock 34.

Why does the sight radius matter?

The longer the longer the sight radius, the more a small error in sight alignment is magnified and since you can see it, you can correct it.

The rear sight in this illustration is .150 inch wide or 3.81mm. If the sight picture is off by just 1mm like it is shown it will affect the bullet impact significantly. How significantly depends on the sight radius.

sight_radius_calc

As you can see a Glock 26 magnifies the sight alignment error by over 40%. That is significant.

What does this have to do with sights?

We consider sight radius when buying a gun and then forget about it when buying sights.

The stock Glock rear sight is horrible and the general industry consensus is that it is only there to fill the rear sight channel. It is built with the least machining possible and sticks straight up out of the channel leaving about a quarter-inch of rear slide available behind it. That space can be used to increase the sight radius.

A common aftermarket self-defense sight is the TruGlo TFO. It combines both fiber optic for day-time visibility and tritium for low-light visibility. It seems like it would be the best of both world, right?

differences in the profile and sight radius

In this photo you can see the differences in the profile and sight radius of these sights.

I had/have these sights and what I found is the very long profile of the sights actually reduce the sight radius down below that of the Glock 26 on my Glock 19. This difference was significant enough that I notice a large improvement in both speed and accuracy when I switched to my preferred Warren Tactical Sights.

The Warrens take full advantage the space behind the rear sight channel and use a fairly short front fiber optic sight. This both helps it be more durable and retains as much sight radius as possible.

In fact a Glock 19 with the Warren Sevigny Sights has a sight radius less than a quarter-inch shorter than a factory Smith & Wesson M&P9.

warren_v_amerigloTFO