I have the Gen 5 G17 MOS with an RMR mounted and it's totally fine (I purchased the appropriate mounting kit and installed it with proper torque + blue loctite).  I don't understand why some people don't like the MOS system.  What is the issue?

I had one and the lack of thread engagement between the optic and plate didn’t inspire confidence, in reality it’s probably just fine as long as it’s installed correctly

This is a big one. That is why there are companies that make MOS compatible plates that offer a lot more thread engagement as well as not needing a sealing plate (if you have a RMR)

Nothing wrong with the MOS. It does raise the site higher compared to some of the milled slides, but nothing really wrong with it. I do recommend getting an aftermarket plate depending on the optic you use.

yes , the optic should thread directly onto slide not some bullshit plate then slide.  Also slide should be milled for a perfect fit for each optic.  Anything less is half ass.  IMHO

http://www.warriortalk.com/showthread.php?123381-The-MOS-is-a-POS

Oh yea that too, kinda surprised the industry didn’t standardize on a mounting platform so we could have factory milled slides without the plates

the plates, the plates.....
But really, no plates.

Makes sense.

I have 9000 rounds on my 34 mos with a dp pro. Never had any issues with the optic flying off. Loctite and 15 lbs torque should be good to go

CHPWS RMR V3 plate.

FCD OPF G RMR MOS Plate

Two good options for aftermarket plates that are better than the factory MOS plate.

Overall, the MOS is fine.  The vast majority of people won’t have an issue with it.  Yes, there can be problems, but they’re few and far-between and the vast majority of people who bring these issues up wind up referencing the same few cases posted online.  It’s not some catastrophic failure of a system, and there are tens of thousands of these guns out on the market and being used by police, and the actual documented failures rest in an extreme minority.  If this is a concern, there is a solution.

The chief issue lies with the adapter plates being made by MIM, so when a plate is cast, it cannot be machined to specific tolerances.  As such, there are plates that are slightly warped.  When the plate is warped, it causes an issue with screw thread engagement and actually leverages opposing screws upward, which then can lead to screws breaking or loosening.  Glock could solve this by switching using plates made out of machined ordnance grade steel.

The second issue people make light of are cheap screws.  The screws could be better, which is why it’s easy enough to go online and get some replacement screws from McMaster-Carr.  The mounting screws you want are part# 94414A712, which are M3x0.50mm x 6mm Torx Plus screws, and have a tensile strength of 140,000psi, with a Rockwell38 hardness.  

The thinness of the plate causes the third issue, which is minimal thread engagement for the screws mounting the optic to the plate.  

So to solve all of this, it’s as easy as getting a replacement plate from an aftermarket company.  The best plates are from CHPWS, as they solve every problem.  They are machined aluminum, fully flush and square, have upgraded screws, and the optic mounting hole doubles as additional recoil bosses, and they double the amount of thread engagement with the optic mount screws.  For most optics, the CHPWS is superior.  TangoDown has an outstanding ACRO plate made out of ordnance grade steel, which I’m currently running on a G45 MOS.  The Glock MOS issue is simply the plates and screws.

As part of an agency T&E process, I ran factory mounting components on a Gen4 G17 MOS with a RMR RM06 for 2.5 years, and I had zero issues.  We ran 4 Glocks in different configurations with factory MOS components, and all were problem-free for the test period, which ranged from 1.5-2.5 years.  I beat the piss out of the optic, and I did pretty much everything to it that Aaron Cowan does to his, minus the drop testing.  The key here was that I was fortunate to have a factory plate that sat flush and wasn’t warped.

Direct-mounting is the most reliable, and the benefit is that you have perfect tolerances and a setup that is the most durable and accurate.  The downside is obviously that the slide is then slaved to a single optic footprint, and changing to a different optic footprint will mean getting either a new gun, or at least a new slide.  If you run an RMR, direct mounting means you won’t have to rezero the optic after a battery change.  

The increased mounting height can be an issue for the Delta Point Pro due to it having a very high main body housing, but with all other optics, the slight increase in height is really a non-issue.

If you have an MOS and you have concerns about the durability of the whole system, you can always have it machined by Agency Arms for their AOS plate system.  I have another Gen4 G17 that has the AOS plate system on it, and the AOS is the superior plate system.

With the aftermarket plates stated above (I like the Forward Controls one) the downsides of the MOS are pretty much negated.

I use a Unity Atom slide.

Where are these steel plates from CHPWS ? All I see on their website is aluminum plates .

I had issues with my GLOCK 19 Gen5 MOS. Damn RMR kept coming loose like every 200~300 rounds.

Yes I had the Trijicon mounting kit and blue Loc-Tite but the kept loosing zero.

Finally after a couple months of constantly tightening the screws, I stripped a mounting plate. GLOCK replaced it no questions asked. They actually sent me two complete mounting kits.

Put a new one on and within a couple weeks, loose again. Sold my GLOCK 19 Gen5 MOS, bought a GLOCK 19 Gen5 FS and took a drive to Jagerwerks, they machined my slide and I've got over 3,000 rounds on it, haven't had to re-tighten the screws once.

That said, I already had a GLOCK 19X that Jagerwerks machined, it has a few thousand rounds on it also and the RMR has never come loose. I just wanted the MOS so I could have the option of mounting other optics IF it came up but fuck it, GLOCK's are cheap.

I had my MOS back when CHPWS was on like V2 plates maybe and people were breaking them on other pistols so I didn't want to screw with aluminum and we couldn't get anyone to make one out of steel at the time. Even though we have new steel mounting options now, I'd rather just have a slide machined as needed and buy a new GLOCK is I get a new optic that is not the RMR foot print.

Never hand a single issue with any MOS gun I set up.


They were properly degreased, loctited, and torqued.  

That being said, they didn’t return to zero during a battery swap, and had too much reliance on screws to keep the optic from moving.

The FCD plate is the way to go for MOS guns and makes the most of the concept, but the MOS system is adequate if you set it up properly.

Did you put RMR directly on the slide, or sealing plate first? I have a g45 on the way that I will send to Jagerwerks as well.

My bad.  Looks like I got a bit punchy on the info.  CHPWS are aluminum.  TangoDown uses ordnance grade steel.  I corrected the post.

If only the RDS MFG'rs would adopt a single standard.

Thousands of rounds and over a year with my Gen 5 17 + ACRO and zero issues. Same zero, same screws, same loctite, witness mark is still showing they're tight. I unfortunately break things often and this setup is still running strong

I've had zero issues with two MOSs now and my primary Gen5 G19 goes to training once a week and I haven't experienced any issues in 18 months and 4000+ rounds.

Like you I used the mounting kit, screws, blue Loctite and correct torque.

That said I did buy a Forward Control Design plate for when I change the battery in my RMR. If for no other reason than I love their AR stuff and figured I'd support them in this adventure.

Totally agree

I just picked up a new 19 MOS a couple of weeks ago.  The RMR plate was warped and was raised in the rear.  I bought the CHPWS aftermarket plate and it worked well after some work with a file.  My only other Glock is a G36 that I've had for 19 years and no problems, but the 19 is having feeding issues.  I'm not impressed.

To the point of bent/warped plates: Plates being warped can also be from screws that are a touch too long protruding below the plate when the optic is mounted.  

If you’re going to run this system, it’s in your best interest to make sure the screws aren’t long enough to do that.  

I’ve had to grind a decent amount of MOS mounting kit screws to prevent this from happening.  

Don’t forget the degreaser.

Yes I used the Trijicon mounting kit which is the plate and two screws.

Tons of people have no issues though, I'm just not a fan based on my personal experiences.

Both of my Jagerwerks machined GLOCK's also have the sealing plates as well as the Jagerwerks screws. They included sealing plates and mounting screws with the machine work.

I wonder about the failures caused by not using a torque screwdriver... but I really doubt most would admit that after a failure!

Any of the aftermarket adapter plates compatible with Glock 40 MOS? looking at getting one of those...