The Glock 40 Gen4 MOS is a semi-automatic pistol chambered in 10mm with a 6.02-inch barrel and the Modular Optic System (MOS) cut on the slide. The long barrel increases muzzle velocity and gives a longer sight radius compared to the standard-length Glock 20, which shows in accuracy at extended ranges. 
 

Key Specifications 

• Manufacturer: Glock 
• Model: 40 Gen4 MOS 
• UPC: 764503002656 
• Caliber: 10MM 
• Action Type: Striker Fired 
• Capacity: 10 Rounds 
• Barrel Length: 6.02 inches 
• Weight: 2.8 lbs (28.2 oz) 
• Finish Color: Black 
   

Detailed Features 

The MOS configuration lets you mount red dot sights directly to the slide using the included adapter plates, eliminating the need for aftermarket milling. Glock's Safe Action system layers three internal safeties so the pistol only fires with deliberate trigger pull. The Gen4 frame includes interchangeable backstraps to fit different hand sizes, and the grip texture is more aggressive than earlier generations. 
 
The 10mm round delivers meaningful stopping power for both hunting and defensive use. Recoil is more pronounced than 9mm but manageable given the full-size frame. 
 

Usage 

The G40 is a niche tool that does a few things well: hunting medium to large game as a sidearm, backcountry carry where bear protection matters, and precision pistol competition. It's less practical as a carry gun given the size and weight. The MOS cut makes it easy to add an optic without gunsmithing.

Owners of the Glock 40 Gen4 MOS in 10mm generally respond well to the combination of the MOS platform and the 10mm cartridge. The long barrel and optic-ready slide are the features that come up most in positive feedback, with users noting the accuracy improvement over shorter-barreled 10mm options.

The 10mm caliber draws a lot of discussion about its versatility. Hunting applications, self-defense, and bear country carry all come up regularly. Reliability gets the standard Glock treatment in owner feedback: few malfunctions reported across high round counts.

The ergonomics are generally well-received, though the size is a recurring caveat. Shooters with smaller hands note that the full-size frame can be awkward, and many point out it's not a practical daily carry gun. The Gen4 backstraps help with grip fit but don't fully resolve the size concern for everyone.

The large aftermarket ecosystem for Glock parts gets consistent mentions from owners who want to customize triggers, sights, or controls. Price is considered reasonable relative to comparable competition in the long-slide optics-ready category.