About GLOCK's MOS (Modular Optic System)

GLOCK's MOS, or Modular Optic System, a proprietary configuration developed by the company to streamline the installation of many popular optics (and expand compatibility) is trending right now.

But what is the Modular Optic System, and should you care? Or is it all hype?

Let’s take a closer look.

Before we get into GLOCK's MOS, let’s talk a bit about some of the shortcomings of most handguns on the market today.

Many of them don’t have mounting points for shooting accessories; leave alone WMLs and lasers, many of them don’t even have good compatibility with most slide (or receiver) mounted optics, like red dot sights.

Granted, there are some handguns that are designed for compatibility with slide-mounted optics, but generally, you’re restricted in scope not only by product offering but also by the footprint of the optic.

GLOCK’s Modular Optic System changes all that. What it is, at its most basic, is an adapter plate that is designed to be mounted to the handgun’s slide, and which will increase its compatibility with several major lines of slide-mounted optics.

There are two basic configurations to the GLOCK MOS, the Standard and the Slimline MOS.

In the Standard MOS, there is a single adapter plate that is compatible with Trijicon, Ameriglo, and Holosun reflex/red dot sights (with the exception of the Holosun 509).

The Slimline MOS pistols do not need adapter plates as they are already cut for specific micro-optics.

There are several significant advantages to the use of reflex optics (like red dot sights) over iron sights.

With a reflex sight, like a red dot sight, there is a single point of light projected onto the lens of the optic, superimposed over the sight picture. In this configuration, you literally “point and shoot.” Red dot sights are generally free from parallax distortion, allow you to keep an open sight picture, and enable rapid, accurate shot strings. They are also suitable in all light conditions.

While iron sights do not contain batteries and therefore are suitable in all conditions (including in the dark with night sights) they require a shooter to line up the sights. Since handguns have a short sight radius (the distance between the front and rear sights), small aberrations in aim and handling can correspond to wide misses on the target.

Therefore, the ability to expand a GLOCK with a red dot sight through the Modular Optic System is a massive advantage.

To summarize, the GLOCK MOS allows you to run a red dot sight, which offer the following advantages over iron sights:

• Faster target acquisition
• Better suitability in both light and dark conditions
• Ability to adjust the red dot sight to engage targets effectively at both closer and intermediate ranges
• Fast follow up shots
• Instinctive shooting from uncomfortable positions
• Freedom from the need to line up the sights

Using the GLOCK MOS is simple. Just:

• Remove the GLOCK cover plate on the slide.
• Select the proper GLOCK MOS plate for the optic you intend to install.
• Tighten the MOS plate on the slide with two Torx screws.
• Once the MOS plate is appropriately installed, install the optic according to the manufacturing instructions.

As you can see, the use of a GLOCK Modular Optic System does not require a trip to a gunsmith and the customization can be made at home requiring only basic tools.

A critical thing to note about the GLOCK MOS is that, based on how it installs on the slide, it does not interfere with the position of the rear iron sight.

This puts it in contrast to some other handgun slides, which require the removal of the rear iron sight before a slide-mounted optic (like a red dot sight) could be installed.

The GLOCK configuration is superior because it allows you to run both your iron sights and your red dot sight (or other reflex sight) as co-witness to each other.

That means, with the right height of iron sights, you can see them through the optic - either at the bottom of the sight window (referred to as bottom-of-window or lower-third co-witness) or perfectly in line with the red dot (referred to as absolute co-witness).

In other words, the GLOCK MOS doesn’t require you to give up your iron sights, you can use them for co-witness, or as a backup, if your red dot ever fails or the batteries die.

Do you still have questions about the GLOCK MOS, or about any of the red dot sights and other optics we sell here at Kiesler Police Supply? Get in touch with us directly and we would be more than happy to help.