This article originally appeared at AmmoLand.
I suppose Glock 17s and 19s go together like a set of wrenches. One size in the toolkit just isn’t enough. The Glock 17 Gen 4 is great for duty, recreation, home defense, and competition. With the right holster, there’s no reason you can’t carry one concealed. The Glock 19 is ideal for concealed carry with its ½ inch shorter overall height and .7-inch shorter length. So, it seems logical that Glock released two new MOS (Modular Optic System) models on both the G17 and G19 platforms.
As with the Glock 17 MOS, the Glock 19 MOS shares identical dimensions and operating specifications. However, in the case of the Glock 19 MOS, the sight radius is identical between the two models.
The Glock 19 MOS also ships with three magazines. These pack 15 rounds each plus one in the chamber.
With that said, there are some obvious differences. Let’s take a look.
The Modular Optic System (MOS)
The MOS models come from the factory with a slot milled out of the top of the slide just forward of the rear sight dovetail. The slot is just about two inches long and maybe 3/16 inches deep if you remove the cover and included optics mounting plates. The gun comes with a “cover” plate installed which basically fills this gap completely, so at a glance, the Glock 19 MOS looks like a regular Glock 19 Gen 4 model, except for the visible seams.
To mount an optic directly to the slide, you simply remove the cover plate and replace it with one of four included adapter plates. These plates are clearly numbered one to four and are cut with posts and holes specific to a variety of optics mounting systems.
Compatible optics (at this time) include:
Plate 1: Docter, Meopta, Insight
Plate 2: Trijicon
Plate 3: C-More
Plate 4: Leupold
For my test of the Glock 19 MOS I used a Trijicon RMR RM01 and mounted it to the G19 MOS using plate number two. Installation took less than a couple of minutes and Glock includes an Allen wrench and extra screws used to remove the cover plate and install the correct adapter plate. Once the right adapter plate in installed, just mount the Trijicon RMR (or optic of your choice) to the plate and you’re off to the races.
Like the Gen 4 models, the new MOS comes with backstrap panels. The pistol comes with the permanent grip sized for the “short frame” size and rear mounting backstrap panels attach to the grip to create “medium frame” and “large frame” sizes. Glock includes a longer pin and a pin punch tool to remove the trigger housing pin that passes through the upper rear side of the grip. To increase the grip circumference, just push the trigger housing pin out, rock a backstrap into place, and insert the longer pin to lock it in place.
The Glock 19 MOS comes with a medium backstrap which adds .08 inches to the circumference and a large backstrap that adds .16 inches. The new twist is that there are two of each size. One is a standard backstrap while the other adds a significant beavertail that extends a good quarter inch past the small beavertail built into the frame.
I like the new beavertail backstraps. While I’ve not had a problem with slide bite from Glock pistols, the new shape allows you to get really aggressive with a high grip.
Mounting an Optic
The mounting plate included with the Glock fit perfectly with the RMR. Two “posts” on the front of the plate fit into stabilizing and positioning holes on the bottom of the RMR and the two screw holes line up with screw holes in the Glock provided mounting plate. The installation process is simple. Using the included Torx wrench, remove the cover plate. Next, replace the cover plate with the correct mounting plate for your specific optic. Glock provides shorter Torx mounting screws that you use to mount the plate, so be sure to use those. Once the plate is mounted, then you attach your optic with a separate set of screws.
One glitch I ran into was that the Glock mount relies on use of the RMR screws provided by Trijicon. My particular RMR was the hi-mount model, which simply means that the basic RMR is screwed onto a taller Picatinny rail mount. The screws that attach the RMR to the Trijicon high mount are a tad too long to use when mounting the RMR to the Glock plate, so you’ll have to acquire shorter compatible screws. I did not have a basic RMR without the mount, so I can’t verify whether Trijicon includes shorter screws with different packagings of the RMR without the rail mounts. Not a big deal, but it’s something to be aware of so you can plan accordingly.
Once I got the RMR mounted, I noticed that the standard Glock sights won’t co-witness through the RMR window. That’s a preference issue, not a checkmark against the MOS. Some people who switch to an pistol optic want a nice clear view of the relatively small viewing window while others may choose to accept some obstruction from iron sights in return for increased redundancy in case the optic fails. Again, it’s just something to know. If you care about co-witnessing iron sights with your optic, you’ll need to plan in swapping out the Glock factory sights for something a bit taller. I only had a Trijicon RMR during the time I had the Glock MOS, so I can’t speak to how other makes of optical sights do or don’t co-witness with the MOS.
Carrying the Glock 19 MOS
My big question was, can you carry it? Well, of course, you can carry pretty much anything if you set your mind to it. I wanted to find out if the G19 MOS would work with commonly available holsters and carry scenarios.
Here’s what I found.
The Glock 19 MOS with RMR mounted fit perfectly in my well used CrossBreed SuperTuck Deluxe holster. While the optic came close to interfering with the front belt clip, it didn’t. Considering the forward cant of the mount, the sight did not take up any space as it is positioned under the slide. So, no concealed carry “real estate” was sacrificed with this configuration.
I also tried the Glock 19 MOS with RMR mounted on a couple of OWB slide holsters – an Andrews Custom Leather model and the DeSantis Mini Slide. There were no problems with either of these either.
I did find a bit of trouble with a Milt Sparks VersaMax. The RMR did touch the leather back panel under the forward belt clip just before the Glock was fully seated in the holster.
I think the moral of this very informal and small sample size test is that it’s certainly possible to carry the Glock 19 MOS with an optic mounted concealed, but the devil is in the details. There are too many possible combinations of optic and holsters to try here, so just try before you commit.
The Bottom Line
The new Glock 19 MOS is the same model 19 that you know and love, just with a new capability to add optics without cutting up your slide. I found the mount to be solid and versatile. I’m looking forward to spending more time with this configuration.