GLOCK is one of the most famous pistol brands in the world, used by military units, police forces, and countless firearms enthusiasts. Its design is simple and austere (very “Austrian”), yet with more than proven effectiveness. 

The GLOCK license for airsoft replicas is exclusive to Umarex, which finally offers fans of this brand the long-awaited MOS range within its pistol lineup. 
• Caliber: 6 mm 
• System: Gas/CO2 
• Magazine capacity: 17 BBs 
• Inner barrel length: 97 mm 
• Weight: 650 g 
• Muzzle velocity (CO2): 290 FPS with 0.20 g BBs

MOS System (Modular Optic System) 
The “MOS” in the name of this model refers to the Modular Optic System, a system designed to allow the installation of optics or red dot sights integrated into the pistol slide. 

This system includes a cutout in the slide, accessed by removing the two upper screws. One of the four footprint plates included with the pistol is placed over this area. These plates act as bases so that the red dot can sit correctly on the slide structure.

Plates 
The plates are numbered 01, 02, 03, and 04 and are designed for red dot systems from brands such as: 

• Docter 
• Trijicon RMR 
• Leupold DeltaPoint 
• C-More STS

To play airsoft, you will need to look for replicas of these sighting systems. To give you an idea of the difference, a Trijicon RMR can cost around 800 euros in Europe, while its airsoft replica is priced at around 30 euros. 

Fitment 
In our tests with the RMR plate and five red dots from different brands (all Trijicon reproductions), we were unable to achieve a perfect fit. This is because the plate lugs, which should mate with the underside of the RMR, are thicker and do not fit correctly.

Performance and Power 
This model is designed to be used with both gas magazines (compatible with previous G17 models and versions) and CO2 magazines that use 12-gram cartridges.

The CO2 system offers more stable pressure compared to gas and is less affected by ambient temperature, which is an advantage in winter. This is especially important because each CO2 shot must move the combined weight of the following elements: the metal slide, the red dot plate, the red dot itself, and most likely heavier BBs. 

The autonomy of CO2 magazines, as is common with this type of system, is approximately 40 shots (equivalent to two full magazines), although this may vary depending on the rate of fire and ambient temperature.

Who is behind this MOS model?

The new GLOCK 17 GEN5 MOS may be manufactured by Star Rainbow (known for the SRC brand), a Taiwanese factory that appears to have replaced VFC in its development. Although Umarex has not confirmed this information, it is plausible.

Does this change anything? 
External quality remains equivalent to previous models, using the same polymers and metal slide. The main difference lies in the hop-up system, which returns to a more traditional design. 
Additionally, gas magazines from previous models, such as the GLOCK 17 and GLOCK 17X, are fully compatible with this MOS model.