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GLOCK released their MOS, or Modular Optic System, line of pistols a year ago. With the ability to mount a variety of reflex-style red dot optics to the slide, the GEN4 MOS offerings kicked off with big guns suitable for hunting and competition: the G40, G41, G34, and G35. Building on that success and much to the surprise of, well, nobody, GLOCK has given the MOS touch to two of their most popular pistols, the G19 and the G17. I promised Gaston’s gang that I could keep a secret and got my hands on these guys in early December, immediately turning the G19 into my EDC. . .


As the G19 and G17 are two of the most popular pistol models in the world and are used as a basis for comparison in just about every polymer-framed and/or striker-fired handgun review, plus are already reviewed on TTAG here and here and here, I’m not going to re-review them. These are GEN4 GLOCKs, and they’re functionally identical in every last way to the typical GEN4 G19 and G17, other than the MOS components. It’s a GLOCK. You know exactly what you’re getting. These two have proven to be no exception. MOS, then. . .


Each MOS comes with four mounting plates to fit the most popular reflex sights. I have a 4MOA dot JPoint, which is a great little sight, but apparently isn’t popular enough to warrant an MOS plate of its own or a listing in any compatibility guide. Good news, though, as it fits perfectly on plate #04, which is billed as being for the Leupold DeltaPoint. However, you’ll need to pick up a pair of M4x0.7 or M5x0.7 metric bolts.


From the factory, a blanking plate is installed on the MOS pistols.


It fits nicely and makes the guns look like their non-MOS compatriots. The first step to mounting an optic is to remove that blanking plate.


Once you’ve chosen the correct mounting plate for your optic, use two of the provided bolts to attach it to the slide. GLOCK has already applied the thread locker.


Mount the optic to the plate, and you’re in business.


The mounting plates are serrated to match up with and effectively extend the slide serrations. I haven’t been shy about using the optic for racking the slide, though. It obviously works extremely well for that purpose — lots of purchase — and so far it doesn’t seem to mind.


GLOCK’s complaint folder is overflowing with gripes about the MOS guns’ factory sights. And by factory, I mean the exact same polymer sights that come on the non-MOS versions. They’re too short to co-witness with any of the reflex sights that fit the MOS mounting plates. Well, other than my slim little JPoint…


It’s just low enough to allow almost full alignment of the factory sights without losing view of the front one. Actually, it would be better without the factory rear sight in place, as the JPoint has a rear sight notch molded into it that happens to work pretty dang well with the factory GLOCK front. Plus I tend to prefer an all-black rear sight anyway.

Since co-witness heights will be different with just about every optic out there — all of them (as far as I know) are taller than the JPoint — it makes sense to me that the MOS guns just come with the standard, cheap sights. I’d guess that most MOS owners would replace them no matter what, and taller sights would risk the chance of actually blocking the dot on some optics. At any rate, if co-witnessing is on your checklist then you’ll definitely be exploring the near-limitless GLOCK sight aftermarket.


As mentioned, the G19 MOS has been my everyday carry since early December. It’s likely to remain in that role until summer, when I may or may not switch back to a slim little 9mm single stack job. I picked up a mess of kydex to try out, and so far so great. The Cook’s Holsters IWB with adjustable clip holster (reviewed here) works just as well for the G19 as it does for my other EDCs, and with the larger size of the GLOCK I decided to dive into the deep end of appendix carry with the help of the guys at T.REX ARMS. Their Raptor is imminently concealable, and the Sidecar adds a backup mag to the mix. I also picked up a Fenrir OWB that fits both the G17 and G19. Reviews after I break ’em in further.


While the JPoint’s auto brightness adjustment dims it to near-off when it’s in the dark of IWB concealment, helping the 2032 battery last a few months, any electronic sight can die at the wrong time or break for various reasons. This is why backup sights are so important on a defensive-use firearm and why, in a case like this one, they need to be tall enough to be visible through the lens of the optic.

Well, at least if you want to hit targets at longer ranges. A lot of people are actually slower with a red dot on a pistol than with irons, and Nick reminded me that it’s because they’re waiting to find and center the dot. At typical self-defense ranges, forget the dot and just use the reflex sight’s frame like a ghost ring — if it’s visible inside the screen, you’re on target and well within minute of bad guy. For this sort of use, the ability to align the iron sights doesn’t matter. Live battery or dead, dot or no dot, broken lens, etc, you still have a self-defense sight picture.

But getting back to stretching out the range, if that dot is down then the irons absolutely come into play. That would be a shame, though, as a nice red dot is awesome for accurate shooting with a pistol. Especially with the sights on most self-defense pistols, which are designed for quick acquisition and rough alignment rather than high precision. At 3, 7, or 15 or so yards this is ideal, but move back to 50 yards and the confidence level and speed drop. The 4 MOA dot on this JPoint is fine enough for head shots on torso silhouettes out to 100 yards, even if reliably making those shots is a tough ask. Torso hits, though, are available on tap.


The G19 and G17 MOS pistols are the same GLOCKs we’ve come to know and trust. They do, however, open up a world of optics possibilities that don’t easily exist with the standard models. The addition of a red dot can be a big plus for competition, hunting, self-defense, teaching new shooters, and more. Red dots are as simple as it gets for sight alignment, and the right dot can provide bullseye-hitting confidence out to significantly longer ranges than most of us would attempt with standard pistol sights. These little reflex optics are surprisingly unobtrusive for CCW use, and I expect we’ll continue to see more and more optics-ready pistols from GLOCK and most other manufacturers hitting the market in the future.

Specifications (GLOCK G19 GEN4 MOS and G17 GEN4 MOS)

MSRP: $726 (both models)
Everything Else: Identical to standard G19 GEN4 and G17 GEN4

Ratings (out of five stars)

Accuracy: * * * * *
Compared to the non-MOS versions, the ability to slap a red dot on it ups the accuracy potential. Not the gun’s, per se, but definitely the shooter’s.

Customization: * * * * *
Any GLOCK is going to get five stars here, as the aftermarket support is the strongest in the pistol world. Add the ability to easily mount optics, and the MOS versions are really at five stars-plus.

Overall Rating: * * * *
To preempt freakouts, please remember that the overall rating is not the cumulative total of the ratings above it but, rather, takes into account all aspects of the gun, explicitly rated and otherwise. I’m not the biggest GLOCK fan in the world. I’d likely rank any of them at three stars, and feel free to input * * * for all of the missing categories above. After all, GLOCKs are the standard. But then I’d give ’em a well-deserved fourth star for stellar reliability and durability. Optic or not, the MOS guns still have standard GLOCK triggers, plastic GLOCK sights, GLOCK ergos (GEN4 did improve on that a bit), and BLOCK looks. So four stars it is for a pair of very good guns, one of which is my new EDC.

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    • That would require a very large investment in a legitimately new product and would result in a significant hit in the profit departments. And since many European countries have significant portions of their public pension funds invested in supposed “private” European companies and stock prices and profits have to stay high to avoid the whole pyramid collapsing, that just isn’t going to happen. Not to mention that despite ads to the contrary, Glock hasn’t even perfected its pistols yet. Which is why there was a long delay in the first MOS models reaching customers that had ordered them months and months before. A buddy of mine got his almost a year after it was supposed to be there and many months after he plopped down a nice pile of cash on a sight. Apparently Glock STILL hasn’t figured out that if you significantly increase cartridge power or significantly lighten the slide, you have to increase recoil spring strength to compensate or the gun beats itself to death. Although I suspect they were beating the optics to death first.

    • Great question. I would buy the G19 MOS in a heartbeat if I had the $700 for the pistol, $100 for a new holster and $200+ for an optic, but I don’t have a $1,000 burning a hole in my pocket.

      The new slide and necessary adapters should be compatible if everything else is identical. I imagine that the slide and adapters would only run about $150 and I could drop a few hundred dollars…. if anyone finds the slides being sold separate, please share.

    • Just this week I e-mailed Glock about this very subject. They replied very quickly and said no, they will not be selling only the slides.

    • Any competent gunsmith can install an “optic” on a Glock pistol. If you want it recessed, they can do that, too. And make it look much more custom and well-engineered than Glocks typical “one size fits all” approach, which actually makes the installation more complex than it needs to be and creates two potential failure points for the mounts. Between the pistol and the plate and between the plate and the sight.

  1. I’ve found that up close, only a few yards, getting your front sight on target is faster than doing so with the dot. But once you get to medium and long range (for a pistol), or you or the target are moving, the dot is way faster. I’ve been shooting my ATEI G19 with rmr for a while now.

    • Yeah but as mentioned in the review, I wouldn’t even suggest looking for the dot at close range. Just use the frame of the reflex sight as a sort of picture window. At self defense ranges that’s more than accurate enough, and once you get into normal shooting position that dot is going to center itself. Also, when I’m drawing the pistol and raising it up before firing, I’m still tracking the front sight as usual and as that front is coming down and my arms are going out and the sights are getting close to alignment, the dot appears. It’s very easy to try and track the frame of the optic instead and wait for the dot, but tracking the front sight as usual will get you into normal alignment even faster. Close range, though, focus on target with both eyes and “ghost ring” with the optic’s frame.

      • What possible defensive use do you have for a pistol beyond “close range”. If the “bad guy” isn’t an immediate threat to make physical contact with you, you have time to do things besides find the dot, put it on the bad guy and start shooting. Like draw your gun, warn him or her, call for help, run, etc. And it’s not like the MOS platform is going to lend itself to concealed carry. My guess is that Glock is looking to make up some of the pile of money it lost on yet another answer to a question nobody really asked, and the additional pile of money it lost while trying to do the typical Glock thing and swap parts and cartridges around and pretend recoil energy and slide mass aren’t important. Which led to the first MOS pistols beating themselves and optics to death when Glock tried to put 6″ 10mm MOS slides on 9mm frames. My buddy ordered one primarily for hunting, plopped down a chunk of change on the “Glock recommended” sight and was supposed to have it months in advance of deer season. Instead he got it months after deer season. Why? Because damned if putting a 6″ 10mm barrel in a lightened 9mm slide made lighter still by carving a big chunk out of it and then putting a 9mm RSA in it didn’t lead to extreme slide velocities. Destructively extreme, even. And then he almost KaBoom!ed it when he decided he was going to “outgun” my .460 Rowland-converted 1911 with his 10mm Glock. He blew a case but the gun survived. He learned his lesson. Mainly that 10mm really ISN’T “in the same class with .44 Magnum”. With 200s at 1500+, my Rowland is.

  2. I replaced a RMR for the JPoint on my G40 for the reasons mentioned. I ran 250 rounds through the G40 last week in 1.5 hours. No issues and so easy to use the JPoint from 5 to 25 yards.

  3. I hope the Glock shop will offer this as a retrofit. I want to put an optic on my G20, and i like the look of this system. …and I’d rather pay Glock than Lone Wolf.

    • Yeah when I read the price I said “ouch” very firmly in my brain.

      This is probably not an upgrade I’ll ever be doing. Maybe when my eyes start to go? I feel like I’d just do a laser guide rod at that point, though.

    • Meh, at a bare minimum you are going to pay a competent gunsmith a minimum of $125 to mill the slide for a red dot. If you want them to retain a rear sight dovetail thats going to be ~$25-50 more. If you ever plan to run the gun without the optic mounted you are going to pay them another $25 or so to cut you a block off plate so you don’t have a gaping notch in the slide. You may decide you don’t want bare metal exposed on the slide under the cutout so you may get the slide refinished which could be anywhere from $50 on up to 3x or 4x that much depending on what option you choose.

  4. Quick question about the rear sight on this. Does it appear to be compatible with standard rear sights available for the non-MOS Glock 19? Comparing Google searches for the two leads me to believe the rear sight on the non-MOS G19 is about 1/8-1/4″ further up the slide. Is that about right? If so is there still enough room to mount say a Trijicon suppressor sight (its not perfectly centered and slightly reflexes to the rear of the dovetail) on the rear without it hanging off the back of the gun?

    I have been shopping for an RDS compatible 9mm ever since I spent nearly 11 hours trapped in a car with Tyler listening to him rant and rave about his RDS equipped M&P on the way out to and back from Pecos (also somewhere in the middle I got to watch helplessly as he wiped the floor with me and pretty much the rest of the field in the pistol shooting stages with the aforementioned M&P).

    So in my quest I got a chance to play with an M&P Pro CORE recently, and liked it for the most part, but the biggest bummer was that the suppressor sights S&W installed look and feel a little cheap, and more importantly they are just plain white three dot sights, no night sights like an FNX Tactical or similar. To my knowledge nobody makes extended height night sights for the CORE series or any M&P for that matter. I think Ameriglo makes an extended front sight post, but nobody makes an extended rear sight for the CORE or standard M&P. Which is irrelevant because the dovetail on the CORE doesn’t match the non-CORE M&P or anything else on the market since most people who put an RDS on their M&P mill out the old dovetail to mount the sight and have a Glock dovetail cut in front of the optic to provide a better co-witness with the RDS. Even if the CORE did have the standard M&P rear dovetail the sights would hang off the back of the slide by 1/4-1/2 inch. Hopefully Glock has not been so shortsighted (get it? haha).

    I like these special versions, but it is moderately annoying when you lose compatibility with regular aftermarket accessories. Because as cool as these are, there isn’t a huge incentive to make something for only a small percentage of the market. Hopefully these things become way more mainstream to force the aftermarket off its collective ass, because if you are going to mixing and matching parts you might as well just go with something custom.

    • A comparo of the pictures here and my G19 confirm that the dovetail on the MOS is further back than the non-MOS version, my Ameriglo sights would certainly hang off the back of an MOS slide.

    • CZ Custom sells one. I’ll have SHOT Show photos and a video booth tour with Angus Hobdell up in the next day or two. (it’s a fully pimped-out P-09, so it’s more $$$ than these Glocks)

  5. It’s like 150 more retail for an mos than a regular new gen 4 glock, after a while and the novelty wears off it will probably be a 100 difference. Sure u can spend 350 on a line wolf mos slide but why? Spend the extra get a glock mos and u have 2 guns and way better resale value….

    • I think the main benefit of the Glock MOS system is that it’s compatible with most of the reflex optics on the market. The aftermarket slides are milled for one specific optic and there’s no way to modify that later. Of course, on the flip side when it’s milled for a specific optic it gets bolted directly to the slide, whereas with the Glock there’s an adapter plate between slide and optic.

      It is a pretty large price jump vs. the non-MOS Glock, but considering how much additional machining is required plus the fact that it comes with a kit of 4 adapter plates, the blanking plate, and extra hardware, the cost makes perfect sense as it clearly costs Glock more to manufacture these.

  6. How long do the batteries last in the red dot? If I carry for a few hours a day what can expect regarding reliability of the sight and battery life?

    • Oh like a year or more if the gun is mostly in the dark. The sight is always on, but if it’s in the dark then the dot is really, really dim. It automatically gets brighter based on ambient lighting. My G19 is either in a bedside safe or concealed on my person, so it’s in the dark 99.5% of the time. This battery was installed in November and it’s going 100% still. I’ll probably swap it out in May for a new one, though. Thinking I’ll do that every 6 months. I have a 20-pack of Sony lithium CR2032s that ran me $8.00 so they aren’t exactly expensive batteries. I’d probably swap them more often if the sight didn’t have to be removed from the gun to do it. However, I’ve already taken it off and put it back on two times and confirmed that zero was not affected.

  7. What length were the machine screws used to mount the jpoint to the plate? want to make sure I have them on hand when the optic shows up.

  8. I just ordered a Glock 19 MOS and a JPoint red dot. You said ” However, you’ll need to pick up a pair of M4x0.7 or M5x0.7 metric bolts.”
    What length did you purchase and where did you get it?? What type of head?

    Than you very much.
    P.S. Excellent write up and info !!!

      • For my mos and jpoint, I ordered these on ebay, and they worked fine with blue Loctite:

        M4 – 0.70 x 6mm – Qty 10 – LOW HEAD SOCKET CAP Screws – DIN 7984 Blk Alloy 10.9

  9. I’ve had Glocks now for over 20 years. Many different Gens and calibers. I’ve been carrying a Gen 4 Glock 26 with Trijicon HD sights (orange front sight, and Pearce +3 mag extensions). and have a few other Glocks currently. I started off about a year ago with an FNX 45 Tactical with Trijicon RMR as my first red dot. I had a gun store mount and adjust the sight for me, then followed by a S&W M&P CORE 9mm with the same set up. These guns are so easy to co witness the red dot. Last weekend I got the G19 MOS at a gun show for $569 plus tax, and was so happy. I wound up coming home and having my local gunsmith mount Trijicon Tough and Bright suppressor height night sights, and mounting the RMR from the S&W on it. I then bought a Vortex Venom for the S&W (since that’s just a target/range gun). The issue I had was the plate kit didn’t come with the correct size screws to mount the RMR and when I went to the range yesterday to dial in the red dot, as I was shooting what I thought was the correct size screws, one actually fell out, and the other once came loose. I even used lock tight. I got home to find several different sized screws from my original install on the S&W, and found some that work till I can get the actual size needed. Anyway. Once I get the dot dialed in correctly (which for some reason on this gun is a pain in the ass compared to my two other pistols) I will use this for my EDC. It already fits in several of my IWB and OWB kydex holsters. I use a MTac Minatour holster for most of my IWB carries, and a custom kydex for OWB that allows me to carry with my Streamlight TLR 1 HL (630 lumen) light. I do sometimes carry one of my compact HK’s or Sigs as well, but this new G19 MOS might just be my favorite carry pistol.

  10. I’m sorry, but a company that brags and brags about reliability should make a mos mounting plate that is durable. After 2000 rounds on my G34 MOS with trijicon RMR, the mounting screw sheared off. I’m working on drilling and tapping it out, will likely incur the cost of a local gunsmith or overnight shipping to Glock under warranty, and loss of the use of this gun for a while. I don’t have a substitute as this build was in the range of $1200 total. So it broke, I’ll eventually get it fixed, but I think Glock has designed a system that needs stronger mounting hardware. The two screws are tiny, Screws are M3x6 6mm, smaller than the ones that fasten the sight to the plate. The gun performed very well, until it didn’t. “Glock Perfection.” Well….

    • Same thing just happened to me with my G19. The 2 screws attaching the MOS Mounting Plate to the slide sheared off and the plate with the sight attached flew off. Slide is now at the machine shop getting the screws drilled out. Had fired over 1,000 rounds over 4 months with no problem but I think the screws attaching the plate are too small. I emailed Glock but no reply so far. I would not trust this set up as it is now.

  11. Its very amusing watching all these Glock guys suddenly decide a Glock with an optic would be really cool now that Glock has a factory option to install them. Its almost as amusing as watching some of the others complain about the cost and complain about not being able to work around the cost or the cost to have a gunsmith do it. If you’ve lived this long without an optic on your Glock, you can probably get along without one. And if you have to have one but don’t want to buy an MOS pistol or pay for a gunsmith to clone the MOS system on your existing slide so you can go back and forth between optic and no optic like on the actual MOS, here’s an idea. Buy a second slide, have it machined specifically for the optic of your choice and when you want an optic put that slide on. When you don’t, put your stock slide on.


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