Getting frustrated---how often are your dots and mounts coming loose?

[dogcaller]

In class I see mounts failing far more than the optics themselves.

A good first step is to understand how thread lockers work:

https://pistol-forum.com/showthread....er-information

...because a lot of people out there have absolutely no idea what they are doing. They mean well, but they are hopelessly wrong.

Once you understand a bit about how fasteners and thread lockers work, you know what variables you need to control.

Re-examine your cleaning process prior to mounting. Whatever thread locker you use, it's crucial that you carefully degrease and decontaminate the threads both in the hole and the fastener. When it comes to removing old thread locker and other gun, I find pipe cleaners really kind of suck. I've taken to using precision brushes from McMaster-Carr:

https://www.mcmaster.com/4905A12/
https://www.mcmaster.com/4754A782/



...because they are small enough to fit inside the threaded holes on most slides and durable enough to allow you to actually scrub well enough to remove a bunch of crud.

So if you handed me your gun and asked me to re-mount things here's what I'd do:

1. Obtain new fasteners for the plate if at all possible.
2. Using a dropper or something similar, put some 99% isopropyl alcohol in the screw holes of the slide and let it sit for a couple of minutes.
3. Using the precision brushes linked above, scrub the living bejeezus out of the screw holes in the slide. This will probably destroy the brushes...but I'm fine with that.
4. Use some compressed air to blow out the holes, then go back to steps 2 and 3 a few times.
5. While letting the slide dry, get a small tray or an old bit of tupperware you don't care about and put enough of the isopropyl alcohol in the tray to soak the fasteners. Let them soak for a few minutes.
6. Using a toothbrush and some tweezers, give the fasteners themselves a good scrubbing. (Note - I wear nitrile gloves when doing all of this to keep oils from my skin from being a problem)
7. Set the fasteners out on a clean shop towel or something to dry.
8. Once the threaded holes and fasteners are completely dry, I will apply a little Vibra-Tite VC3 on the threads of the fasteners. I will use a fine paintbrush (that has been cleaned in the alcohol) to force some of it into the recesses of the threads. Let this sit for 5-10 minutes.
9. Apply a drop of VC3 into the threaded holes in the slide. The drop will sit at the very top and not go down into the blind hole unless poked with a toothpick or metal pick to allow the trapped air out.
10. Affix the plate to the slide and then begin to thread in the fasteners.

If you've used the right amount of thread locker, a little bit of it will start to ooze out around the head of the fastener when you torque it down. This is key, as it helps hold the fastener in place as well. A good application fills in the gaps between the thread surfaces and any small gaps between the screw head and the slide.

11. Clean up any excess or spillage that happened on the slide. (Q-tips, paper towels, etc)
12. Set the slide somewhere it won't get subjected to temperature extremes for at least 24 hours.

Using that exact process I've mounted optics to my shotguns and to multiple Glock MOS pistols without anything coming loose for literally thousands of rounds of shooting. I've set my Glocks aside in favor of running my customized M&P's, but prior to that they went through just shy of a combined 25,000 rounds without the plates budging an iota.

YES, those brushes are what I need! I have a 2-day USPSA class next weekend and with my work schedule I won't have time to have them shipped, get it mounted, cure, and zeroed before I have to leave, so I'll see if I can luck into something local -- maybe Grainger? Thanks!

[JCS]

In my higher round count guns it’s happened once.

Sig p320 7-8k rounds. Mounted once and it has never moved or lost zero.

Staccato P. Loosened up after 150 rounds because I didn’t use the proper torque. After I retightened screws it hasn’t moved in 3k rounds.

I have no secrets. I just tighten to the exact specs the plate mfgr recommends. I did use the e6000 stuff on my Sig.

[TCinVA]

YES, those brushes are what I need! I have a 2-day USPSA class next weekend and with my work schedule I won't have time to have them shipped, get it mounted, cure, and zeroed before I have to leave, so I'll see if I can luck into something local -- maybe Grainger? Thanks!

Grainger might well have something similar. It's worth a shot.

[TC215]

@SoCalDep has arguably mounted more optics than anyone here and recommends against VC3. I’d be curious as to whether his opinion has changed over the years.

I’ve mounted optics with VC3 that have worked and stayed tight. I’ve seen more failures than successes. I think it’s a poor product for use with pistol optics. If it worked then I do think you are lucky.

[DaBigBR]

The "problem" with VC3 seems to be that it's just not forgiving enough. Most folks don't let it set long enough before threading fasteners in. I also question whether it is too thick for some thread pitches. My success rate with 242 is very high. My success rate with VC3 is pretty low. I have probably mounted 50-60 optics on slides.

[oregon45]

In class I see mounts failing far more than the optics themselves.

A good first step is to understand how thread lockers work:

https://pistol-forum.com/showthread....er-information

...because a lot of people out there have absolutely no idea what they are doing. They mean well, but they are hopelessly wrong.

Once you understand a bit about how fasteners and thread lockers work, you know what variables you need to control.

Re-examine your cleaning process prior to mounting. Whatever thread locker you use, it's crucial that you carefully degrease and decontaminate the threads both in the hole and the fastener. When it comes to removing old thread locker and other gun, I find pipe cleaners really kind of suck. I've taken to using precision brushes from McMaster-Carr:

https://www.mcmaster.com/4905A12/
https://www.mcmaster.com/4754A782/

...because they are small enough to fit inside the threaded holes on most slides and durable enough to allow you to actually scrub well enough to remove a bunch of crud.

So if you handed me your gun and asked me to re-mount things here's what I'd do:

1. Obtain new fasteners for the plate if at all possible.
2. Using a dropper or something similar, put some 99% isopropyl alcohol in the screw holes of the slide and let it sit for a couple of minutes.
3. Using the precision brushes linked above, scrub the living bejeezus out of the screw holes in the slide. This will probably destroy the brushes...but I'm fine with that.
4. Use some compressed air to blow out the holes, then go back to steps 2 and 3 a few times.
5. While letting the slide dry, get a small tray or an old bit of tupperware you don't care about and put enough of the isopropyl alcohol in the tray to soak the fasteners. Let them soak for a few minutes.
6. Using a toothbrush and some tweezers, give the fasteners themselves a good scrubbing. (Note - I wear nitrile gloves when doing all of this to keep oils from my skin from being a problem)
7. Set the fasteners out on a clean shop towel or something to dry.
8. Once the threaded holes and fasteners are completely dry, I will apply a little Vibra-Tite VC3 on the threads of the fasteners. I will use a fine paintbrush (that has been cleaned in the alcohol) to force some of it into the recesses of the threads. Let this sit for 5-10 minutes.
9. Apply a drop of VC3 into the threaded holes in the slide. The drop will sit at the very top and not go down into the blind hole unless poked with a toothpick or metal pick to allow the trapped air out.
10. Affix the plate to the slide and then begin to thread in the fasteners.

If you've used the right amount of thread locker, a little bit of it will start to ooze out around the head of the fastener when you torque it down. This is key, as it helps hold the fastener in place as well. A good application fills in the gaps between the thread surfaces and any small gaps between the screw head and the slide.

11. Clean up any excess or spillage that happened on the slide. (Q-tips, paper towels, etc)
12. Set the slide somewhere it won't get subjected to temperature extremes for at least 24 hours.

Using that exact process I've mounted optics to my shotguns and to multiple Glock MOS pistols without anything coming loose for literally thousands of rounds of shooting. I've set my Glocks aside in favor of running my customized M&P's, but prior to that they went through just shy of a combined 25,000 rounds without the plates budging an iota.

These posts are why, when I get back into dot guns, it will be with a direct-mill mounted Acro P2.

[TCinVA]

On finer threads you do have to take some care to ensure that it actually gets worked into the threads of the fastener. That's why I actually brush it into the threads to ensure it coats the peaks and valleys.

I started using VC3 on pistol mounted optics because I had been using it years prior on mounting things to shotguns because it worked very well. And shotguns are pretty fucking brutal to anything screwed to them.

[TCinVA]

These posts are why, when I get back into dot guns, it will be with a direct-mill mounted Acro P2.

I'm currently running two M&P's direct cut for the Acro.

I think that's the future of optic mounting. The screw down through the optic mounting standard isn't going anywhere anytime soon, but it's sub-optimal as a way to handle optics on pistol slides. Eventually it will reach the point where mounting a dot is no more difficult on a handgun than it is on an AR. But until then the suffering will continue.

[Pnut]

Has anyone here tried VC3 as a bedding compound yet? I’m curious of the results…

When I had my problems with my SRO constantly coming loose, someone suggested that it might be caused by the extra eight of the optic. This was only and assumption, but I’m curious how many other SRO owners have experienced this…

[SoCalDep]

@SoCalDep has arguably mounted more optics than anyone here and recommends against VC3. I’d be curious as to whether his opinion has changed over the years.

It has not. As I’ve mentioned, I’ve seen VC3 work but I’ve seen it fail at a much higher rate than Loctite.

At this point I’ve completely lost track of how many optics I’ve mounted. It’s in the several hundred range at this point. We do have optics come loose occasionally but it’s rare now (excepting the Springfield Prodigy I’ll mention later!). We’re more likely to have problems with mounting a new optic like today’s EPS to an M&P.

As for using things like E6000 and VC3 as a bedding compound, I’m not sold either way and I have some concerns, but I see how it could help in certain circumstances. The problem is that there’s no standard... How much to use? Where? I know of at least one optic destroyed by too much E6000 when trying to remove it. The DeltaPoint Pro I mounted on a Staccato still moved even with E6000 and when I removed the screws the optic came right off. The E6000 wasn’t holding the optic still at all. Maybe had I used more, but how much more? It seeped out a bit on the sides when I tightened it so I didn’t go crazy light. (Add the fact the optic moved even with the E6000 and fully tightened screws and enter the new Dawson mounting system which is rad and I can’t see that not completely fixing the problem).

The elasticity of E6000 and VC3 is something I think is detrimental to the optic remaining affixed and the screws remaining tight - especially at the low screw torque and high recoil impulse. Elasticity implies movement for shock absorption (which we probably don’t need because optics tend to come loose rather than fail) which to me means more potential for screws to come loose... but I’m no engineer, so ultimately we learn by doing.

Here’s another thing... Sometimes components are a problem. We’ve had defective plates, plates with design defects, optic pockets that have inconsistencies and design defects, screws that are too weak for the torque specs, screws that are too short, threads that are too loose, screws that have heads that are too wide for the optic countersink that contact the optic prior and prevent fully seating, we’ve had people use torque specs for optics when the component is made of aluminum and has a significantly lower torque spec...

All of these things can affect performance and mounting reliability, and bandaids like E6000 don’t fix the underlying disease.

Mounting it right is important, but sometimes when a bad component is used to mount the whole thing is doomed from the start. We can mitigate this with good quality components but it’s still voodoo a bit. I have one Springfield Prodigy in particular (not mine - It’s been great so far) that runs great but the damn optic plate has come loose four times with two different plates and optics. There’s more going on there and I’m almost positive there’s something about the gun that’s a problem. I’m waiting on it getting examined by our Senior Armorer to see what he thinks, but I’ve already told the owner it should probably go back to Springfield for that and a couple other oddities.

There was a secondary question about getting the threadlocking compound off. This is another problem with VC3... Rather than simply prevent movement, it almost functions as a gasket... I believe this contributes to why I’ve seen so many optics come loose with VC3... and it cakes on and sticks to everything. I saw a product called “”Un-Cure” from Bob Smith Industries as a possible thread locker remover. I’ve only used it a couple times, but it worked to get rid of the huge amount of VC3 caked on one pistol, including dripping down into the channel for the extractor assembly and hardening (yes - it was done very wrong... VC3 is less forgiving of not following the instructions because it requires air curing while Loctite is anaerobic).

I’m a little leery of using Un-Cure and then trying to re-mount without really making sure it’s gone, so I’d probably hit the slide with a good cleaning, maybe a Gunscrubber blast or ultrasonic cleaner, then re-mount to make sure there are no remnants of the Un-Cure to foil the new threadlocker. This may be overkill and the Un-Cure may just evaporate away but again... I’m not a chemist or engineer, so I learn by doing.

All that to say... If you’ve used VC3 to mount the optic or if you suspect VC3 was used prior, I’d make sure it’s gone. Un-Cure or diligent cleaning with solvent to remove, then a thorough degreasing.

My method:

1. Make sure the optic works
2. Test fit all components
3. Ensure all components are degreased - I almost exclusively use alcohol wipes and a toothpick to get it into the nooks and threads and such.
4. Apply Loctite 243 or 248 to the bottom 3rd of screw threads
5. Tighten to the lowest torque spec of interacting components - or if you have experience, there are some exceptions
6. Mark the screws/optic body for an early warning. I only mark visible screws
7. Wait a minimum of 24 hours before shooting.

I’ve not shot my LTT yet (waiting on a holster) but I mounted the Holosun 507C optic with McMaster 4-40 screws at 12 in/lbs - I’ve done this a couple times with good results, so we’ll see.

I know this is a long post. It’s long because there is no short “do this and it will work” answer. Pistol optics haven’t become that standardized yet. Hopefully one day. In fact, just today I got a call from an instructor... a deputy in his class had a Sig classic series pistol that wouldn’t run at all. The screws supplied with the C&H plate for the Holosun optic were too long and prevented the extractor from moving (not the first time I’ve seen that - will have to come back to the armory so we can shorten the screw on the right side), and just a couple hours later one of our armorers was trying to use the wrong screws (to wide of a head) to mount an EPS to an M&P - he didn’t know we got stainless screws with narrower heads for the Holosun optics.

I’m proud that we’ve authorized a lot of guns and a lot of optics... It means we make a lot of mistakes and we learn a lot. Thankfully we have some checks and balances in place to mitigate the mistakes becoming a life-threatening problem, but it’s a never-ending battle to stay on top of it all, let alone getting everyone else (instructors and armorers) on the same page.