Gun Review: Glock 40 Gen4 – A 10mm Long-Slide Red-Dot Big-Bore Hand-Cannon

Off the bat, I would call this the F-350 of handguns. Its a ridiculous amount of handgun for most everyday users and one would typically not drive one into the city. Its just unwieldy. But, there is a reason F350s are made as there are users who know what they need to get a big job done. That may be heavy payloads, hauling long-distance, or simply hauling *ss.


Glock puts it this way:

The G40 Gen4 in the MOS Configuration is chambered in 10mm and combines a full 6-inch barrel for an improved velocity with a magazine capacity of 15 rounds. The G40 Gen4 in MOS configuration is a powerful yet easily carried pistol; perfect for the outdoorsperson, hunter and sport shooter. It is designed to give the handgun hunter the ultimate choice in semi-automatic gaming pistol and has proven to be more than capable of taking down game such as Whitetail Deer, Russian Boar and even Feral Hogs.

What Comes in the Box:

The new Glock handgun cases are a huge step up, but I would contend the G40 has outgrown it. Opening it up, the case nearly popped out due to the contents. Everything will go back into the case, just make sure to brush up on one’s Tetris skills.

  • G40 Gen 4 w/ 15 Round Magazine Inserted
  • 2x Spare 15 Round Magazines
  • Spare Medium & Large Backstraps in Standard & Beavertail Form
  • Magazine Load Tool
  • Glock MOS Mounting Plates for Common Micro Red-Dots
  • Factory Test-Fired Rounds for Restricted States
  • Adjustable Sight Tool
  • Child Safety Lock
  • Cleaning Brush
  • Paperwork (Manual, Warranty Cards, Etc.)


Overview & Handling

I expected the Glock to be heavier considering its size, but it was a gentle giant at just over 28 ounces. Now, I would not call it graceful, even for its size. Unloaded, the pistol is front-heavy from the long-slide, but upon insertion of the magazine it starts to balance out (about 40 ounces). Its not until the red-dot is on the top that I found it suitably neutral for extended shooting sessions.

The grip itself is massive. Those with small hands need not apply, even without the back-strap. My wife, who can reasonably hold a medium back-strip G17 9mm found it difficult to simultaneously get a firm grip and reach the trigger. My medium-sized hands found the smallest setting most comfortable, but the medium back-strap most assuring, as I tend to grip high on a gun and get slide-bitten. Unlike other Glock competition-oriented handguns, the G40 does not have the extended slide stop.

I am sure it will be mentioned a few more times, but for handing purposes, its a Glock Gen 4. The grip includes finger groves (which work for me), the square textured grip pattern (which I also like), larger and reversible magazine release, and a too shallow undercut on the trigger guard for the middle finger. It arrives with standard adjustable Glock sights (which work, but are terrible) and interestingly, the rear sight actually overhangs the back of the slide a bit. Not sure if this is an engineering oversight, but its annoying for “perfection”.


Sight overhangs the rear just a tad.

Sight overhangs the rear just a tad.

The MOS System

The MOS system or “Modular Optic System” is a latest and I found surprising addition to the Glock family. Introduced with the G40 and 9mm/.40 smaller siblings, its a from-the-factory optics mounting cut into the slides. This is by no means innovative, as the aftermarket has been doing it for years, but it is useful and actually helps “perfection” get closer to perfection.


Author’s Note- It was disappointing the PFI optic sent separately from Pride Fowler was not compatible with the MOS system. While set up for one of the patterns, the optic sits too far forward to actually be nestled into the handgun slide as intended. I got my hands on a Trijicon mini-dot to test the MOS system (not pictured). 

Drop plate on, drop optic onto plate. Its that easy.

Drop plate on, drop optic onto plate. Its that easy.

Typically, those wanting the functionality had to either buy an aftermarket slide, send it off for milling, or use an adapter plate which sets the optic up higher. Having this done at the factory lends has at least a few advantages. When already loaded in a milling machine, its easy and inexpensive to add the cuts, the cut-out area can be coated instead of being left bare, and ensures tighter tolerances than separate machine loadings.

Just quite didn't fit.

Just quite didn’t fit.

The MOS mounting area sits just fore of the adjustable rear sight. As shipped, it arrives with a flush and profiled plate that matches the slide. The blending is excellent and only those with solid eyes or handing the firearm up close would notice that it could accept an optic. The plate is held on with two torx head screws and removes easily to mount an optic. Adapter plate mount to slide and the chosen optic to adapter plate. Voila.

Once mounted, it brings up another gripe. The factory sights are way too low for any sort of co-witnessing. Considering the cost to injection-mold these, another oversight from Glock. I know there are plenty of aftermarket systems out there, but at least Glock could have made the effort.

Shooting the G40 Gen 4

If one has shot 10mm before, there is nothing truly remarkable about the Glock’s performance. The cartridge, to me, is just like its daughter the .40 S&W. There is some snap to the recoil, which the dual spring and heavier slide do help soak-up, but its not so much that I could go on another paragraph.

20151108_124618 20151108_124559

Accuracy continues to be normal for my abilities with a Glock, but the longer sight radius did help tighten it up a bit, to just over 1.5″ at 15 yards (Freedom Munitions 180 grain RNFP) using the iron sights (I normally shoot about 2″ with a G19). Adding in the optic (provided by PFI – detailed review coming later), I was able to shrink it some more, shooting 2.0″ at 25 yards.

As with nearly any review written on a Glock, the trigger is long, mushy, and a solid Glock. However, I am not a fan of this one, as Glock opted to remove the serrations found on most of their other handguns. This truly accentuates the passive safety, which after about three magazines actually started to cause discomfort in my trigger finger. After a 100 rounds, I utterly detested it. Of course individual preference will rule the day, but this is one Glock that in my opinion, needs an aftermarket booger-switch.

Various groups while out on the range. Top right is at 25 yards, offhand, slowfire. Impressive.

Various groups while out on the range. Top right is at 25 yards, offhand, slowfire. Impressive.

Putting aside the trigger, the MOS system truly shines on the handgun. True to Glocks intended purpose, adding in the optic makes this a “long” range handgun with true hunting potential. For older eyes or simply faster target acquisition on moving targets, the red dot on the handgun shines. With either excellent trigger control or a better bang-switch, the G40 can and does meet Glock’s claims for an excellent hunting handgun.

I will note, though, that to take maximum advantage of the longer barrel hand-loading will be required. Factory 10mm loads tend to be “neutered”

Author’s Note: While Glock specifically disclaims the practice, shooting .40 S&W through the 10mm was possible, if not more pleasurable due to the better slide to powder-charge mass ratio. Glock states this will void your warranty and rightfully so, as one is shooting a round outside of proper head-spacing. TFB and myself DOES NOT recommend this be done at home.

25 yards, fast-fire, off-hand. Full Magazine.

25 yards, fast-fire, off-hand. Full Magazine.

The Good:

  • MOS system is fantastic. Works as advertised and is nearly future-proof as one only needs to buy new plates.
  • Magazine capacity is 15+1 of a big-bore handgun cartridge.
  • Light, relatively speaking, for the caliber. 10mm 1911s are just freaking heavy.

The Notable:

  • Its a Glock, with all the benefits and quirks thereunto pertaining.
  • Its BIG. Really, really big. My small-handed wife could not even comfortably grab it. Medium-sized hands are a prerequisite.
  • Did have the occasional difficult putting it back together.


The Bad:

  • Trigger is smooth-faced, except for the passive-safety, which makes it detestable for long firing sessions.
  • A few annoyances: The rear sight overhang, and the lack of extended slide stop.

Final Thoughts:

The problem with reviewing Glocks is that they are Glocks. There really is never much new about them so writers are left searching for prose. This one is no different. The G40 Gen 4 is a Glock at its core, just a very big one. Its a great handgun for those who want or need 10mm.  If you don’t need 10mm, the trade-offs to get there with the bigger grip and massive size are, in my mind, simply not worth it.

On the other hand, the MOS system for optics mounting is much appreciated and a solid step forward for the notoriously conservative Glock company. With simple plates to mount to just about every conceivable micro red-dot (just not the PFI), its a versatile system that worked well, although I am curious to see how various red-dot systems handle the increased recoil.

Ultimately, the combination of the two makes this a novel Glock. Its a veritable hand-cannon with the 6″ long barrel (although one needs to reload to take full advantage of this length). Further, its reliable, the trigger sucks, and it can mount a red-dot sight without having to find an aftermarket slide or mounting accessory.

So, if you need this much gun, its a solid super-duty. If you don’t need this much gun, go with the smaller option, you will be much happier.


Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • Daniel

    I had been waiting in this gun to jump into the 10mm game. My ocd tells me I will not be happy with the sight overhang. Is this the case with all sights? May just get a Lone Wolf G20 slide/barrel for one of my G21.

    • MR

      Could the rear sight be replaced with a standard Glock rear sight? IIRC, the 20 I looked at a couple days ago had normal sights on it. Kind of a step down, and you may have to replace the front sight to get the height correct, but it’d fix the overhang problem.

  • Full Name

    How much did you pay for this?

    • Kelly Jackson

      More than you can afford pal

      • Full Name

        In other words, if I have to ask…

        • JK

          I’m betting it’s cheaper than most of the plain-Jane 1911s you’re likely to see.

        • Hero5

          Are we talking about ZJs here?

      • Bart

        Glocks are pretty reasonably priced. It’s probably $5-600

      • G0rdon_Fr33man


    • DaveP.

      Looks like they’re running between $650 and $750 NIB on GunsAmerica, though you’d be adding your FFL fee and maybe some S&H to that. They’re still too new to be coming up for sale used with any frequency.

  • Calimero

    It looks like you got the “Competition sights” (a la G34). Import regulations/scoring I assume ?

    I got mine here in Europe with classic/non-adjustable sights. Suppressor sights (something like 1/3 lower “co-witness”) will probably help get the gun back in line and reacquiring the red dot quicker after each shot.

    My G40 being my first handgun with glass I have to admit that I’m slower that with my good ol’ iron sight G17.

    Shooting on the move or on moving targets should be easier with the red dot though. Might also help at longer range.

    And yeah this is my first foray in 10mm land. Reloading is pretty much mandatory here as 10mm is a bit of a Gunny Hipster caliber. Getting 10mm brass is a bit of a nightmare. And reloading is all round cheaper.

    F350 is about right!

  • Mister Thomas

    “The grip itself is massive. Those with small hands need not apply,” … that’s a shame. I thought the Gen4 was a slight bit smaller than Gen3. For those of us who could use a slightly less bulky grip- it’s too bad that it wasn’t possible to make it that way.

    • Calimero

      It is smaller than a Gen3 grip. But we’re still dealing with a “large” .45ACP/10mm frame.

      Without any backstrap, Gen4 grips are supposed to be close to Gen3 SF/Short Frames.

      I don’t have lumberjack hands but I find my G21/G20 Gen4 frame to be really manageable. The agressive texturing helps.

      So I suggest trying it for yourself.

    • J.T.

      With the gen 4 .45 and 10mm guns, the frames are the same size as SF (short frame) gen 3 guns.

      • gunsandrockets

        The short frame is a big improvement over the original 20 grip size, but still a tad bit bigger than a 23 grip.

        If I ever get a 10mm, it will probably be RIA because of the better hand fit (and because of the price!).

  • Edeco

    I’m glad Glock is doing more longslides. If they do a 17L MOS and/or with threaded extension I’m in.

    10mm tho… don’t want that combined with the light Glock frame. It’s like a V8 in a Lotus Eleven.

    • Christian Hedegaard-Schou

      I built a G21SF into a G20L, with a 7″ barrel. Now I can shoot both .45 and 10mm just by switching top-ends.

      The recoil vs the frame weight really doesn’t matter. The long slide and barrel help to soak up a lot of the recoil. It’s actually more pleasant-shooting than my 5″ 1911 in 10mm and my 4.5″ EAA Witness 10mm. Both of which are 100% steel frame guns.

      • Edeco

        Surprising. Still the Witness Hunter…

        Hey, any idea if the 7″ LWD barrel gets more velocity than factory 6″ ? One might assume based on length, but there are other factors…

    • Hensley Beuron Garlington

      Which would be friggin’ awesome! Kinda like, the Hennessey Venom GT! Its basically a Lotus Elise/Exige. Speaking of cars however, John Hennessey originally wanted to put one the Viper V10 engines, twin turbo-ed, in the little Lotus. Now that would of been a good comparison of a 10mm in a Glock.

      But, everything I hear about the Glocks in 10mm have been positive. Or how about that .460 Rowland conversion? Now that I hear has a bit more kick to it and comes with a compensator.

      • Edeco

        If by ‘awesome’ you mean gratuitous. Harumph!

    • billyoblivion

      Is that like shoving a v8 in a Miata?

      If so, I really don’t understand your complaint.

  • J.T.

    “Glock removed the serrations”

    No, they just gave it the trigger that every full sized Glock has. The only reason the compact and subcompact guns have it is so they can meet the required number of points for importation.

  • Duray

    So “MOS system” stands for “Modular Optics System System?”

  • Hunter

    Pull out the trigger and sand down the passive-safety with 600 grit sandpaper. I do this in all my glocks and it makes a world of difference. Just be sure to tape the passive-safety in the forward positon when you sand.

  • El Duderino

    C’mon TFB I know there are deadlines but at least we can have pictures that match the actual setup you used.

  • Evan

    Handguns in general bore me, but I want one of these. 10mm is a cool caliber that they need to make more guns in, and big guns in general are awesome. Glock 20 is better for carry, but other than that, this is a really cool sounding gun.

    • NoNamesOnTheNet

      I carry a G20 Gen 4 on a daily basis. Nothing more comforting than 46 rounds of 10mm fury accompanying you wherever you may venture.

      • Hensley Beuron Garlington


      • MrDakka

        You never know when you’re gonna run across a super mutant

        • billyoblivion

          Probably Saturday or Sunday when I go visit my dad’s side of the family.

          But they won’t like it if I shoot a relative.

      • Jerry

        Why would you do such a thing?

        • NoNamesOnTheNet

          I’m not following you. Why would I carry a 10mm?

          Because I find 9mm too anemic, .40 too compromised, and I like the capacity bump over a G21.

          Haven’t you ever heard the saying “Carry as much as you can conceal”?

          I just so happens to be able to comfortably conceal a full size large frame handgun and two spare magazines.

          • NoNamesOnTheNet

            And the 43 is my backup/deep conceal, in case you were wondering.

  • Lance

    Got to love 10mm its got more power and less snap than .40 S&W has.

  • Christian Hedegaard-Schou

    Living in CA and being a 10mm junkie (I’ve got 6 10mm’s at the moment) I had to build my own G40 since they are “unsafe” and cannot be purchased here.

    I picked up a standard Gen3 G21SF in .45 (I also love and shoot .45, and now I can shoot both just by switching top-ends) and built out a G20L Lonewolf slide with a 7″ G20 10mm barrel also from Lonewolf.

    It’s tons of fun to shoot, and I get a little extra “oomph” from that 7″ barrel over my 4.5″ EAA Witness or 5″ STI Nitro 10 1911, or any 6″ G40. A Pyramid trigger completes everything to make a nice little tack-driver too.

  • TheNotoriousIUD

    I like it.

  • Big Daddy

    Awesome gun!!! I have shot all the 10mm Glocks. Most available ammo is soft shooting not much more than .40 S&W. The G40 mitigates a lot of the recoil which isn’t as bad as one would think. If 10mm full powered ammo was more available it would be in my collection. This is a reloaders type of handgun because of the lack of ammo choices and the expense.

  • TangledThorns

    Yeesh, could that slide be any shorter?

  • sean

    I love my Glock 40MOS! I put a Trijicon RMR on mine and it is doing awesome with the 200 gr. hardcast double taps!!

  • smartacus

    i gots a 6″ hunter barrel on my 20.
    and i’m stull mulling over getting the 9″ barrel from LoneWolf

  • HenryV

    Gosh. Now that is lovely.

  • That is the non adjustable sight pictured. The review handgun came with adjustables.

  • Ben

    Huh, so the lighter bullets gain more from the increase from a 6″ to a 7″ barrel. That makes sense, lighter bullets = more space for powder, and therefore more use for extra barrel.

    • Beju

      Yes, FWIU, the longer barrel theoretically allows for more complete powder burn.

  • Ted Unlis

    With the right ammunition, this 10mm Glock topped with a red dot is an
    efficient and potent candidate for a defensive weapon in bear country, the 6
    inch barrel, lighter weight, and round capacity make the Glock 40 an attractive
    choice for back country hikers or black bear bow hunters sitting in States that allow the carrying of a defensive handgun while
    bow hunting

    • jackalo626

      I have a Glock 20sf and carry it in black bear country Smokey Mountains. Much rather shoot any dangerous critter with a long gun but that just isn’t very practical.

  • I like long slides and I cannot lie… ???????

  • Gavin

    What’s the best gun safe to store a gun like this?