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

[dogcaller]

My first RDS platform is a LTT92. I purchased the pistol from a member here and then purchased the RDS slide from LTT directly. I've had it for about a year, mounting an SRO. I would estimate 1500-2000 rounds on the RDS slide. I noticed a slight wiggle with the base yesterday during dryfire, which means that I will need to detach both the sight and the mount to fix it. This is the third time I have had a sight or mount come loose in the last year. The round count is not that high--it's just frustrating. It's the biggest reason I decided to have my G-17 direct milled for a Steiner MPS--hoping to alleviate this very issue with the crossbolt mounting system. That being said, I'm loving and really concentrating on the LTT, and would like to continue with it.

I have assiduously followed both the directions from LTT (the first and second time) and the best practices advised in the comprehensive thread here on PF, including using Vibratite / Loctite as described.

Each time, I have cleaned out the screw holes as well as I could, again, following directions. In addition to the hassle factor, I worry that mounting and remounting will eventually cause damage to the fine threads drilled in the slide.

Is my experience different than yours, and, if so, do you have any advice?

Thanks!

[Pnut]

I have an STI Tactical in .45 with an SRO and had the same problems. The mounting plate that fit between the slide and SRO would always come loose after a few hundred rounds.

Someone here suggested I bed the plate to the slide with a product called E6000, which is essentially an industrial grade rubber cement. It can be found at most hardware stores. I tried it out and it’s worked great. I’ve only put about 1000 rounds through it since the bedding, but it hasn’t budged yet.

Someone also suggested using VibraTite as a bedding compound, but I haven’t had a need to try it yet. Both products would do essentially the same job… securing the plate to the frame, but also absorbing the shock of the moving parts because of their elastic nature.

[dogcaller]

I appreciate that, Pnut. Will need to check that out.

What's the best way to clean this gunk out? I've used alcohol, plastic picks and pipe cleaners in the past, but I'm not sure that it's getting all of the residual threadlocker residue out. Is there anhy risk/benefit to using carb or brake cleaner? Other recommendations? Thanks

103999

104000

[DaBigBR]

I'd try acetone first. I usually put it on a pipe cleaner and vigorously work over the threads. Acetone will strip a lot of stuff alcohol will not in my experience. It evaporates extremely quickly as well.

[YVK]

Answering your question in a generic way, in 6 or so years running dots on CZs, Glocks, and SIGs I've had optics or mounts come loose twice. A dovetail mount on a Glock 48 and either a DPP or SRO, don't remember, on CZC plate on my Shadow 2. I don't use the Vibra, only blue loctite. No idea about LTT mounting solutions and how it compares to others.

[DaBigBR]

Also, don't reuse screws. Go on McMaster Carr"s website and get the ones you need in bulk. A bag of 50-200 (depending on specs) will be $8-$16. Take a quick inventory of what you have for optics and plates and such and get a bag for each. I know C&H is subject to some mixed feelings on here, but their plate listings provide exact screw specs, which is nice.

[TCinVA]

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.php?50712-Proper-use-of-Loctite-amp-general-fastener-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.

[TCinVA]

I'd try acetone first. I usually put it on a pipe cleaner and vigorously work over the threads. Acetone will strip a lot of stuff alcohol will not in my experience. It evaporates extremely quickly as well.

Acetone is also worth a shot as a cleaner/degreaser. Ultimately anything that will break up oil and other substances we don't want interfering with the performance of the thread locker and won't leave a residue is cool. Loctite makes their own cleaner-degreaser that would also work.

But finding a way of getting good strong mechanical agitation into those threaded holes is a huge boon to keeping plates mounted solid. Anything you can use to facilitate that is a good idea. I've found the aforementioned precision brushes work well and I've been known to resort to actual dental tools to pick out larger hunks of schmutz so I can scrub.

[Archer1440]

VC3 is crap for this application. Full stop, end of story. Use blue Loctite, preferably 248 solid.

(I wrote a long treatise on how and why, but deleted it. There's plenty of other threads on the subject.)

[TCinVA]

I've not had VC3 show up as "crap" for this application in my guns or in client's guns. (To the point where one client who had his optic fail had to buy a soldering iron to remove the CROM from his 1301 so he could ship his busted Aimpoint back) In fact, I've seen fewer failures with it than I have of Loc-tite. VC3 seems to be slightly more forgiving as it doesn't set up with a hard crystalline structure like Loc-tite does, which is a little easier to thwart. Over-application seems to be the worst problem with VC3.

But either will work well providing you observe the holy rituals of decontamination prior to use.

Whatever you choose to use, the majority of success is in the preparation.

[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.php?50712-Proper-use-of-Loctite-amp-general-fastener-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.php?50712-Proper-use-of-Loctite-amp-general-fastener-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:


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

[dogcaller]

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


Yeah, I hear you. It's why my second MRDS is a Steiner MPS, direct-milled onto a G-17. But I really like the Beretta and want to keep using it...

[dogcaller]

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

Found some of those brushes at Harbor Freight. clipped the wire at the end so I could reach in even further and wore out the brush. Also used dental picks, gently, and spent a couple hours on LTT surgery last night. Everything thoroughly cleaned, degreased, new screws (also degreased), painted on the blue Loctite. Will let the slide sit on the mantle until Sunday.

Just realized that I forgot to do a sage smudge before and after--dammit.


Thanks, all, for your help--I really appreciate it.





Edited to add that it still seems like the 10lbs of torque required by the LTT instructions seems a little light, but here we go again...

[LukeNCMX]

Loctite 248 chapstick is the best product for this application.

VC3 is junk mostly because a proper application process is absolutely ridiculous. If someone sold high quality screws at the correct length with pre-applied VC3 99% of the issue with VC3 would be resolved. I imagine it is cost prohibitive because I am pretty sure ND Industries (Makers of Vibra-tite) sell commercial quantities of screws with pre-applied with thread locker.

With all that being said, why put up with VC3?? The only real redeeming quality of VC3 is it is less likely to cause broken screws on removal than loctite. A better solution if you have issues with broken screws on removal is to heat up the screw head with a soldering iron to loosen the loctite before you try to unscrew. You probably won't need to do that if you stop using a factory glock MOS plats, don't reuse the same screws a bunch of times, and stop drowning them in wet loctite.

[EVP]

Apply Loctite 243 or 248 to the bottom 3rd of screw threads


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.





Excellent info as always!

Just a few quick questions if you don’t mind.


Would you mind sharing what specific product or SKU- those McMaster screws you use for the LTT and 507c?

Concerning Loctite:
What do you use to remove and clean old blue 243 loctite?
Have you heard of anyone using green 290? (Maybe a little overkill)


Thanks

[TCinVA]

Edited to add that it still seems like the 10lbs of torque required by the LTT instructions seems a little light, but here we go again...

A dirty little secret of my practices that no one should follow:

I use high quality bits from Chapman because they fit fasteners properly to prevent rounding off engagement surfaces, they are made in America and they hold up to hard use. I tighten the fastener until I feel just the slightest bit of flex in the Chapman bit itself. This is likely a little more torque than is advised.

Like I said, kids...don't be like me.

[DaBigBR]

Loctite 248 chapstick is the best product for this application.

I used to believe that, but found that the stick would dry out and/or become contaminated over time. I think there is also some concern about it getting into the very fine threads.

I have settled on buying larger bottles of 242 or 243. They are easier to shake well (which is important and overlooked), allow more precise application than the small vials you cut or break open, and are easier to adequately re-seal.

[stomridertx]

I used to believe that, but found that the stick would dry out and/or become contaminated over time. I think there is also some concern about it getting into the very fine threads.

I have settled on buying larger bottles of 242 or 243. They are easier to shake well (which is important and overlooked), allow more precise application than the small vials you cut or break open, and are easier to adequately re-seal.

A happy medium is Permatex 24010 Medium Strength Threadlocker Blue Gel. The gel is easy to work with on tiny fasteners. I've had good results with Permatex equivalents to Loctite products, and I like that I can buy Permatex products in Auto parts stores close to me and not have to worry that I'm getting a Chinese counterfeit product on Amazon or eBay (a real concern).

[SoCalDep]

Excellent info as always!

Just a few quick questions if you don’t mind.


Would you mind sharing what specific product or SKU- those McMaster screws you use for the LTT and 507c?

Concerning Loctite:
What do you use to remove and clean old blue 243 loctite?
Have you heard of anyone using green 290? (Maybe a little overkill)


Thanks

For some reason I can’t get the login page to load on McMaster.com, so the best I can do right now is the following:

Alloy steel flat head IP10 Torx drive screws... the dimensions when I measured the included screws were 4-40 x 5/16” for RMR and 4-40 x 1/4” for Holosun. I have found that the 5/16” screws work for Holosun as well and they seat right at the bottom of the plate/T-nut, don’t engage the slide, and so that’s what I used. I always test fit both lengths with the optic and plate and go with what appears to be the best fit.

As far as removing old Loctite, normally I’ll just use a round toothpick with an alcohol swab... getting it into the whole and twisting it around until it’s pretty clean. Un-Cure could be used but I generally don’t find it necessary. I do a lot of optic switching and a lot for others and I haven’t seen any trends of optics coming loose more often after being re-installed or switched.

I wouldn’t use Loctite 290 for optic mounting. It says heat is required for disassembly and Loctite 243 and 248 work fine for my use. The only exception is some of the 2021-2022 era Staccato plates... We would use a (VERY small) dab of red Loctite on the plate-to-slide screws. The optic-to-plate got 248.

[Archer1440]

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).



What you also need to know is that VC3 is essentially acrylic plastic dissolved in a carrier of MEK (Methyl Ethyl Ketone). MEK is therefore an excellent solvent for VC3. There are several different viscosities and formulations of "VC" such as 3, 4 and 5, but all are essentially plastic dissolved with MEK or other solvents.

(Another word for that is "paint").

The other "VC" formulas use other solvents, such as VC4 which uses Ethyl Acetate instead of MEK. These differ mostly by how long they take for the solvent to flash off. But all of them are essentially acrylic paint.

All of these were originally developed for very large threads - as you would find on tank parts. That's the origin of VC3, going back to Vietnam.

Now, the obvious problem is, in many states, especially California, getting your hands on MEK to get rid of the VC3 on an install these days is a major PITA, because it's more regulated. However, it's available through Alliance Chemical, which sells on Amazon. And MEK is a far more effective solvent than Acetone. (Both should only be used in very well ventilated areas with no flame sources.)

[Biggy]

I often wondered why more manufacturers don’t use Spiral lock fasteners (taps and I think bolts also) for things when they do not want things to come undone too easily. I believe the tapped holes and bolts work using tapers on the threads of each that self lock together. When I was running a CNC mill at work we used Spiral lock taps on many different parts.

[maximus83]

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

https://pistol-forum.com/showthread.php?50712-Proper-use-of-Loctite-amp-general-fastener-information

[...]

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.


Great tips in the linked thread on Loctite and fasteners, and here on using the brushes for thread cleaning.