Glock G40 MOS: An Optic-Ready 10mm Powerhouse

posted on July 14, 2021
Glock G40 MOS

Glock introduced its Gen 4 G40 at the 2015 Shooting, Hunting and Outdoor Trade Show. The polymer-framed semi-auto pistol sports the familiar businesslike looks of the company’s other offerings, but this one stood out from the others.

For one thing it had a 6.02" barrel hiding under a long slide (9.02 inches long, to be precise). It also came with the company’s brand-new Modular Optics System (MOS), which made mounting red-dot or reflex sights on the gun fast and effortless—a money- and time-saving virtue enthusiasts have come to appreciate. Glocks with the system ship with their slide milled for optics and base plates that fit the most popular electronic pistol sights are included. The combination makes anchoring an optic DIY, rather than one requiting gunsmith intervention.  

The handgun’s overall is 9.49", a rather cumbersome figure for duty or carry. The setup is ideal for hunters, though, who are more interested in wringing the last bit of performance possible out a cartridge than concealment, and usually prefer an optic over iron sights.

The G40 may not be Glock’s best-known handgun, but it continues to be a popular choice among enthusiasts, for good reason. When B. Gil Horman reviewed one for American Rifleman shortly after its release, he concluded, “The Gen4 frames fit my hands more comfortably than the Gen3 models and the addition of the MOS feature is certainly a plus. The timing of the G40's arrival couldn't be better. Finally, we can enjoy a reasonably priced 10mm long slide with the rugged reliability of a Glock without the need for expensive aftermarket parts or gunsmithing.”

The G40 MOS is chambered in 10mm, magazine capacity is 15 cartridges and the magazine release is reversible. The modular backstrap allows owners to customize feel. The gun weighs 35.45 ozs. empty and—for those not interested in mounting an optic—the pistol ships with an adjustable, white U-notch sight at the rear with a white dot up front. Glock doesn’t list MSRPs, but the gun is running roughly $800 on several reputable FFL websites.


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