There’s a lot more science than meets the eye when it comes to designing handgun sights.

The folks at XS Sights have been making their flagship sight products for years. Known as XS Big Dots, these sights use some time-tested lessons from those classic lever-action guns. The rear sight is a shallow "V-shaped" ramp while the front is a large and very visible dot.

To line them up you just rest that gigantic front dot in the bottom of the shallow “V.” They’re very fast. The only downside is that for precise shooting at longer distances you can lose a bit of aiming precision. For self-defense applications at rational distances, they’re great.

Wanting to keep moving forward with their core competency of highly visible and fast sights for both day and low-light applications, they've just launched a new generation of sights. Known as the F8 line, these take a more traditional approach, at least at first glance. But don't let that fool you. Let's take a closer look.

But first, a science moment.

The Science

The F8 sights use a bright orange ring around the Tritium night sight. This outer ring is intended to be visible in both daylight and low light conditions. Here’s the science part. Orange isn’t orange. The XS folks beat up their paint suppliers for a very special orange that has a lot more yellow than red in the mix. Why?

Red is the first color that your eye starts to lose track of in dim light, at least compared to yellow, which is among the most visible colors in dark conditions. According to the XS folks, most competitors use a heavy red blend in their oranges to optimize for daylight use. This same orange paint is photo luminescent, so when you transition from light to dark, it glows.

That helps during the transition from daylight to very dark conditions where you’ll see the Tritium glow. The more you know.

The size and visibility of the large orange dot is a nod to XS Sights’ heritage. It jumps into view as you raise the gun.
The size and visibility of the large orange dot is a nod to XS Sights’ heritage. It jumps into view as you raise the gun.author photo

Proportions Are Key

One of the engineering tricks to make that front sight with its large dot leap into view is to use a wider notch in the rear sight.

With more daylight between the front sight view and the edges of the rear notch, you have better visibility of the front sight. If you just narrow the front sight to obtain a similar effect, you can get excellent precision in bright conditions, but there is little surface area from which light can reflect back to your eyes, so your eyes are slower to acquire the front sight.

If the front sight is too wide relative to the rear, then there's another problem. It’s difficult to line up a wide front sight with a tight notch in the rear sight because there's little "daylight" on either side.

All of this boils down to a balancing act. In the case of the F8, the front sight is in the middle of the width spectrum—wide enough to fit that large surface area dot, but small enough to allow room for plenty of light on either side when viewing it through the rear sight.

The rear sight also takes a deliberate compromise approach.

Most target and factory rear sights use square cut notches. The eye picks up sharp angles well, but you really don’t want your eye focusing on the bottom corners of the rear sight.

To help combat this, the X8 rear sight is rectangular, but with rounded corners in the bottom, which helps direct your eye to the front sight and keep your focus on the parts of the rear sight that matter: the top edges.

The Dots

In the center of the rear notch, you’ll notice a small dot just below the center of the rear notch cut out. The idea is that you stack the front dot on top of that centered rear dot. The result is a visual figure eight pattern.

In low light conditions, with this configuration, there is no potential confusion over which dots are front and rear, which can happen with classic three dot sight systems, as all the dots look the same. The X8 dots also help with precise and quick alignment of the front and rear sights.

As a bonus, the front of the rear sight unit features a tall and flat surface, useful for racking the slide one-handed, if necessary.

There’s a lot of surface area on that front sight, which makes it fast to acquire. The orange ring is photo luminescent, so it actually glows after it collects a bit of light.
There’s a lot of surface area on that front sight, which makes it fast to acquire. The orange ring is photo luminescent, so it actually glows after it collects a bit of light.author photo

On the Gun and At The Range

To test these new sights out, I replaced the factory SigLite night sights on the Sig Sauer P320 shown in the photos. Using a set of calipers, I took some quick and dirty dimensions for both sets of sights to see exactly how much size difference there is on that large front dot.

On the Sig factory sights, the dot itself measures just about 0.118 inches in diameter. The metal housing of the front sight is 0.139 inches. On the new XS F8 front sight, the dot is about 0.155 inches. That’s over 30% larger—a significant difference. The front sight housing on the XS F8 measured 0.165 inches wide.

My eyes are getting slower by the year at picking up standard sights—for some reason, they get smaller and smaller—so I was anxious to shoot this new set. I wasn’t disappointed.

As a result of all those geeky features we discussed earlier, the front sight leaps into view. And I mean that unambiguously. I started out with some informal raise, sight, and shoot drills. Starting from a low ready, I raised the gun to the target and fired as soon as I got a positive sight picture. The result? Fast, fast, fast. Getting shots on target was quick and confident.

Note the center dot in the rear sight housing. It sits below the front dot for fast alignment, forming a figure eight. Note the rounded corners of the bottom of the notch in the rear sight.
Note the center dot in the rear sight housing. It sits below the front dot for fast alignment, forming a figure eight. Note the rounded corners of the bottom of the notch in the rear sight.author photo

For precision shooting, rather than centering the front post in the rear notch, I tried stacking the front dot on top of the center rear dot that’s just below the rear sight notch. Remember, the front dot is a two part affair. There’s a larger orange dot with a smaller green tritium insert in the center. When the pistol is extended at arm's length, both the rear dot and the tritium center of the front dot appear to be the same size, so it’s easy to place one on top of the other with good precision.

The new F8 sights will roll out for different pistol models over the coming weeks.

The first batch is compatible with 9mm and .40 S&W versions of Sig Sauer P320, P226, P229, and other “P” series models. Those sights also fit the Springfield Armory XD, XD-S, XD(M) and FN 509 pistols. The next batch will roll out for Glock 17, 19, 26, 34, and 43/42. After that, we should see sets for the Glock 20, 21, 27, 30, and 41 followed by Smith & Wesson M&P and M&P Shield Pistols. Release plans can change so check in at the XS Sights website to stay up to date. MSRP: $184.99