Just like in Samuel Beckett's famous play Waiting for Godot, GLOCK fans are always waiting for a new generation of their beloved pistol – this time the Gen 6. In the meantime, however, the five GLOCK generations so far introduced have brought continuous small improvements to a gun that, according to many, was already born perfect. These included, for example interchangeable back straps, a more resistant nDLC surface coating, a new dual recoil spring for reducing recoil, and the GLOCK Marksman Barrel (GMB) for top accuracy. Among the improvements, the Modular Optic System – or MOS for short – was one of the most significant enhancements.
Appearing toward the end of the Gen4 series, around 2016, MOS-equipped pistols are the Austrian manufacturer's answer to the needs of those who wanted a red dot on their GLOCK. The MOS System in fact simplifies the mounting of optical/reflex sights without costly milling or gunsmithing on the pistol's slide, and accepts most major red dot brands from the factory.
GLOCK MOS System, for double-stack and single-stack (Slimline) GLOCK pistols
The MOS System in available for both standard double-stack GLOCK models (they come with one numbered GLOCK MOS Adapter plate) and for Slimline single-stack models – Slimline MOS pistol models have slide cuts designed for specific micro-optics and do not include adapter plates. Each GLOCK MOS adapter plate set contains one numbered adapter plate, three 6 mm/0.24 inch (M3x6) Torx screws, two screws to install the GLOCK MOS Adapter Plate and one replacement screw. All screws come with drop of glue applied.
Installing your optical sight on a GLOCK pistol in MOS configuration is quite easy, and can be done in just five quick steps. Here comes a short description who you can do it on your own:
1) Remove the GLOCK cover plate first;
2) Select the appropriate GLOCK MOS adapter plate, place it in the correct position and orientation;
3) Tighten the two Torx screws to fix the GLOCK MOS adapter plate on your GLOCK MOS pistol;
4) Verify tightness of the screws, depending on ammunition and frequency of use (if a torque wrench is available, the optimum fit is 1.5 Nm / 13.3 lbf. Inch, and if you often need to screw on and unscrew, make sure to apply another drop of threadlocking type adhesive to the thread of the screws);
5) When the GLOCK MOS adapter plate is completely mounted on your GLOCK MOS Pistol, install the optical system of your choice according to the directions of the manufacturer. Bob's your uncle.
In case you have a Slimline GLOCK model, after removing the cover plate you can directly mount the specific MOS sight on your slide, making sure to use a M4x8 mm flat-headed screw.
Video: GLOCK MOS System – configuration and installment
All available GLOCK MOS models and calibers from Gen4 to Gen5
Today, most 9mm GLOCK pistols are available in MOS configuration; MOS models are also available in .45 ACP, .40 S&W and 10mm Auto. In more detail, according to GLOCK website there are 9mm GLOCK MOS variants for the long slide G17L Gen5, G47, G17 Gen4 and Gen5, compact G19 Gen5, subcompact G26 Gen5, competition G34 Gen4 and Gen5, and compact G45; MOS slimline models include the subcompact G43X and G48 (both also available in a set complete with RMSc Shield reflex mini sight). In .45 ACP: G21 Gen5 MOS and G41 Gen4 MOS. In 10 mm Auto: G20 Gen5 MOS and G40 Gen4 MOS.
For more information please visit the GLOCK website.
