I picked up this PSA Dagger slide / Holosun optic combo on sale. It’s sitting on an SCT-19 frame right now. Functions perfectly and is super accurate.
I’m having a problem with the optic screws loosening up after about 100 rounds. At first it was properly torqued using the loctite blue that comes on the screws. The first time it came loose I added some additional chapstick type loctite blue.
Came loose again today. I typically shoot about 150 rounds or so at each range outing so things get pretty warm.
Tonight I’m cleaning the screws off completly and I cleaned out the threads on the slide with some alcholol. Not sure if the cerekote is contributing to the problem.
What loctite do you guys recommend. I’d like to be able to take it apart without too much hassle but at the same time I don’t want it coming loose during use. Thanks.
Stainless steel is not reactive to loctite, but the screw steel should be. Except the screws are somewhat passivated by the black oxide so not sure how reactive the steel screws would still be.
There is a loctite primer product that allows curing with inert metals. Ive never used it.
The threads in the slide are cerekoted. I wonder if that is hindering the loctite. I May go with a drop of red. Can’t have this thing loosening up all the time.
Use alcohol/alcohol wipes to degrease screws and screw holes. Then let it set up for 24 hours. I set my slide, optic down, so the locktite does not run into the extractor depressor plunger channel. This is after torqing to manufaturers spec, 10-15 in/lbs.
I use blue 242 on most AR parts that need put in place besides any gas blocks that clamp or have set screws. Clean everything up, put a drop on the screw, and you should be good.
I just cleaned the screws, threads in slide and reapplied some loctite blue (chapstick style so it’s not running anywhere). Screws are torqued properly.
If this doesn’t work I’m going to try the vibration VC-3 next. Thanks for all the suggestions.
I’ve been using a small bottle of Vibratite 131 that I got a while back. Never had issues except for my last HE509T plate being stuck on. Normally it’s easy to apply, lasts beyond it’s expiration date, cures to shootable within an hour or two, and is usually easy to remove when I don’t over-apply it. Supposed to compete with Loctite 262 (red permanent), but I’ve found it’s removable without heat.
Somehow magically breaks free when needed, but not under firing. Had about 7000+ rounds through a G34G5 using that as threadlocker for my HE407C, on a CHPWS plate. Never touched the screws at all after they were installed.
My experience with blue Loctite has always been bad. Over-applies too easily, and has always required a gunsmith to forcibly remove the screws for me, damaging them. Usually because STUPIDLY, optic screws use Torx. Great in theory, but the Torx bit used is so small that you lose all the benefits of the “larger surface area”. If using blue, I’d switch out to larger-bit + screws. Never had an issue getting those out, or twisting/shearing bits or the screw itself.
Same. Works great, but is still able to be fairly easily removed when needed. Loctite blue wasn’t cutting it, and red can just be a pain if you ever need to remove parts. I switched to Vibratite VC-3 a few years ago, and like it much better personally.
Of course after cleaning and reassembling with blue (not the holosun factory applied stuff but the chapstick type stuff) it held last range outing. Next time it comes lose it’s VC3
, but because stainless steel is a “passive metal,” it cures much slower than regular steel. To get a strong bond, you must choose the right product—such as LOCTITE 243 or LOCTITE 567—and thoroughly prep the metal. [1, 2, 3, 4, 5]
1. The Challenge with Stainless Steel
Loctite anaerobic threadlockers and sealants cure in the absence of air and through contact with active metal ions (like iron or copper). Stainless steel is highly alloyed with chromium and nickel, meaning it lacks these active ions and is considered “passive.” As a result, standard formulas may cure incredibly slowly or require a chemical activator. [1, 2, 3, 5]
2. Best Loctite Products for Stainless Steel
For the best results, use products specifically engineered to cure properly on passive metals:
Threadlocking (Bolts & Fasteners): Use LOCTITE 243 (Blue, medium strength) or LOCTITE 242. These are surface-insensitive and designed to work well on stainless without requiring a primer.
Thread Sealing (Pipes & Fittings): Use LOCTITE 567. It is specifically formulated to cure on passive metals and acts as a high-lubrication sealant, which helps prevent the galling (seizing) common with stainless steel pipe threads. [1, 2, 3, 4]
3. Step-by-Step Application Guide
Clean the metal: Stainless steel surfaces can be slick. Clean both the bolt and the nut/thread using a degreaser or brake cleaner to remove any leftover machining oils or grime.
Use a primer (optional but recommended): If you are using an older or standard Loctite formula (like standard red or blue), you should spray the threads with Loctite SF 7649 Primer. This speeds up the cure time significantly on passive metals.
Apply the product: Apply a few drops of Loctite to the engaging threads of the fastener or pipe.
Assemble and cure: Tighten the assembly to the manufacturer’s torque specs. Allow it to sit undisturbed for at least 24 hours for a full, maximum-strength cure. [1]
I have been using Vibra-tite V3 for a few years now and really like it. You do need to put it on your fasteners and let it dry before you install your fasteners. Some people complain that it doesn’t hold properly but that is because they didn’t read the instructions on using Vibra-tite.
I also have Red, Blue and Purple Loctite that I use for different applications. One old gunsmith trick that I have also used for years on small fasteners is clear nail polish as a threadlocker. If you are scared of stripping out a small screw head trying to remove it, then a little nail polish remover on and around the head of the screw will help soften the nail polish so you don’t strip out your small screw heads.
One thing to be careful of is to keep the threads of the 30cc/ 1oz Vibra-tite bottle clean and don’t overtighten the black plastic cap on the glass bottle. The cap is kinda brittle. I tried to use a pair of soft jaw pliers when I couldn’t undo the cap by hand. The cap cracked the threaded portion of the cap. I had to transfer the remaining Vibra-tite to a small plastic squeeze bottle to keep it from gumming up in the glass bottle.
