Glock's Modular Optic System (MOS) and milled slide options represent two popular methods for adding red dot sights (RDS) to your Glock pistol. Choosing between a Glock MOS and a milled slide significantly impacts the gun's aesthetics, functionality, and overall cost. This in-depth comparison will help you decide which option best suits your needs and preferences. Understanding the differences between Glock MOS and milled slides is crucial for any serious Glock enthusiast looking to upgrade their carry gun.
Understanding the Glock MOS System
The Glock MOS (Modular Optic System) is Glock's factory-integrated solution for mounting red dot sights. Instead of milling the slide, Glock MOS pistols come with a pre-cut slide featuring four adapter plates. These plates accommodate various popular RDS brands like Trijicon RMR, Leupold DeltaPoint Pro, and Shield RMSc. This system offers several advantages:
- Reversible: You can easily switch between different RDS models by simply changing the adapter plate. This versatility is a major selling point for shooters who might want to experiment with different optics or upgrade in the future.
- Factory Warranty: Because the MOS system is a factory-installed feature, it typically doesn't void your Glock's warranty. This peace of mind is valuable for many gun owners.
- Cost-Effective (Initially): The initial purchase price of a Glock MOS pistol is generally lower than a custom-milled slide.
However, the MOS system also has some drawbacks:
- Height Over Bore: The adapter plates add height to the optic, potentially affecting the sight picture and co-witnessing capabilities.
- Plate Reliability: While generally reliable, there have been isolated reports of adapter plate issues, highlighting the importance of using high-quality plates.
- Limited Optic Selection: Although it supports several popular optics, the MOS system isn't compatible with every red dot sight on the market.
The Allure of Milled Slides
A milled slide involves a gunsmith professionally machining the slide to create a custom recess for a specific red dot sight. This method often results in a lower profile optic mount compared to the MOS system.
Advantages of Milled Slides:
- Lower Profile: The milled slide usually sits lower to the bore, leading to an improved sight picture and potentially faster target acquisition.
- Custom Fit: A milled slide provides a perfect fit for your chosen red dot sight, ensuring a secure and stable mount.
- Improved Aesthetics: Many gun owners appreciate the clean, integrated look of a milled slide with a flush-mounted optic.
Disadvantages of Milled Slides:
- Cost: Professional milling services can be expensive, significantly increasing the overall cost of adding an RDS to your Glock.
- Irreversible: Once milled for a specific optic, the slide is typically not easily adaptable to other RDS models. Switching optics would require re-milling the slide.
- Warranty Considerations: Modifying your slide by milling can potentially void the manufacturer's warranty. This is a crucial factor to consider before proceeding.
Choosing Between MOS and Milled: A Decision Matrix
| Feature | Glock MOS | Milled Slide |
|---|---|---|
| Cost | Lower initial cost | Higher initial cost |
| Versatility | High (easily swap adapter plates) | Low (fixed to one optic) |
| Height Over Bore | Higher | Lower |
| Warranty | Generally maintained | Potentially voided |
| Aesthetics | More bulky, less integrated look | Sleeker, more integrated look |
| Installation | Easy, can be done by the user (with correct tools) | Requires professional gunsmith services |
Case Study: Comparing Two Glock 19s
Let's compare two Glock 19s: one with a factory MOS and one with a custom-milled slide and Trijicon RMR. Both guns are used for concealed carry.
The Glock 19 MOS user reports quick changes between different RDS for different situations, but notes a slightly higher profile and less aesthetically pleasing setup. The milled Glock 19 user raves about the lower profile and cleaner look, but mentions the higher initial investment and the inability to easily switch optics.
Conclusion: The Best Choice for You
The best choice between a Glock MOS and a milled slide depends on your individual priorities and budget. If you want versatility, affordability, and maintain your warranty, the MOS system is a good starting point. If you prioritize a low profile, custom fit, and a sleek aesthetic, a milled slide is the better option, but you need to budget for the higher cost and potential warranty implications. Carefully consider your needs and preferences before making a decision. Remember to factor in the cost of the red dot sight itself, as that is an additional expense for either method.