Back at Big 3 East in October, I got a chance to try a Glock 40 MOS. For those not familiar with that model, it is the equivalent to a Glock 20L. The Glock 20 is the full size 10mm Glock. It uses a similar frame as the Glock 21 .45ACP. I have a Glock 21 and Glock 41, the long slide variant of the Glock 21. I assumed the Glock 40 would be built off the Glock 41 or at least similar to it. How wrong I was.
The Glock 21 is known for its massive slide, however the Glock 41 has a narrow slide. Kind of like the Glock 30S. The Glock 41 slide is akin to a Glock 34/35 long slide. The slides are similar with the Glock 41 being just slightly longer by 4mm. How does that relate to the 10mm Glock? Well the Glock 20 and 21 share similar dimensions and frame. As I said before, I thought the Glock 40 and 41 would be similar as well.
Below you can see the sublte differences in slides.
In the photo above you can see how long the Glock 40 slide is compared to the Glock 41 and yet it is as wide as the Glock 21 slide. This is why I think the Glock 40 should have been labeled as a Glock 20L. The slide and barrel are similar length to the Glock 17L and Glock 24 (the .40 S&W long slide).
Below is a comparison of the Glock 40 barrel with my extended threaded Glock 21 barrel by Lone Wolf.
The MOS line of Glocks allows the user to mount a red dot to the slide. Below you can see the cover plate has been removed. There is a ridge machined down the middle to keep the adapter plates from shifting and thus helping to maintain zero on the optic.
Here is one of the adapter plates installed onto the Glock 40 MOS.
To my surprise, I was able to mount my Meopta Meored to the Glock adapter plate. Something I am unable to do with my FNX-45 Tactical.
Unfortunately the Meored does not co-witness the factory iron sights. You would need taller suppressor sights if you wanted to have irons that co-witness through the red dot.
The Glock 20/40 10mm magazines have similar dimensions to the Glock 21 magazine bodies so I tried using magazine extensions on the Glock 10mm magazines. Below you can see a +2 mag extension from SGM Tactical’s .45 acp Glock magazines as well as a KRISS MagEx extension normally used on my Glock 21 magazines to feed my KRISS Vector.
Below I swapped the slide onto my Dark Earth Glock 21 Gen4 slide.
This setup should hold 35 rounds of 10mm however I was unable to get it to work. I have read online that some people have had some success getting a KRISS Vector mag extension to work on a Glock 20 magazine. I tried some minor modifications to make this work but unfortunately I was not successful.
With the large heavy slide on the Glock 40 MOS, shooting the handgun was very tame and mild. My friend helped test it and we were hitting targets out to 100 yards with relative ease.
And for those that missed the joke, “This is my Glock 40. This is my problem solver right here” is a reference to some street thug who was interviewed and said that line while holding a HiPoint pistol.
That is not the case here. The Glock 40 is real and it is a 10mm that solves a lot of problems.