I purchased a new tri lug adapter for my obsidians to use on the MP5 clones. My concern is that the thread protectors seem to unthread when shot without suppressors. I am a bit concerned about the thread protector coming unthreaded when I have the tri lug adapter used on a suppressor which could be bad. What is the best way to avoid the thread protector coming unthreaded? Loctite? Better way to hold that thread protector in place?

rubber o-ring then put on thread protector...

Either O-ring or a tiny drop of Rocksett.

Loctite is temperature sensitive.

I use an o-ring with my SP5 and trident 9 with no problems.

I'm scared that its going to come off with serious consequences and there is no need for it running suppressed. I just remove it.

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Originally posted by hrcjon:
I'm scared that its going to come off with serious consequences and there is no need for it running suppressed. I just remove it.

Bad idea. The area in front of the tri-lug is designed to be provide alignment by being a close fit with the inside of the sleeve/piston that’s in the tri-lug adapter of the suppressor. By removing the TP, you’re removing something that helps keep the suppressor aligned. The lugs are mainly only there for locking. Depending on how strong the spring is, you may be able to get away with it, but you’re taking a chance of getting a baffle or endcap strike.

I think the TP unscrewing inside of the tri-lug is nearly impossible. What is the motive force that would cause the TP to completely rotate at least 5-6 full turns inside of the adapter and come off of the end?

quote:

What is the motive force that would cause the TP to completely rotate at least 5-6 full turns inside of the adapter and come off of the end?

Weirder things have happened; I'd say it is certainly possible. As previously recommended, a drop of rocksett would be good. I have also had good luck with thread tape, using direct thread cans; it could work well here as well.

quote:

Bad idea.

OK fair enough and thanks for getting me to rethink it. I'll generally go back to reinstalling it with locktite. But I think the answer overall is it depends. My normal HK and B&T don't have this problem as they only have trilug so I gave the issue some thought initially when I got a barrel with both options. So when I first decided to remove the thread protector on one gun with this dual mount system I mounted my suppressor 3 lug adapter (by itself) and the threads were not in the adapter. So my conclusion is that thread protector or not it can't affect anything.
But after your note and now that I look at a couple of other guns with the same dual option setup I see a variety of lengths between the tri lug and the threads. The spec for the HK tri lug shows 30mm of barrel after the lugs. And in one of the other barrels I measured it was exactly that to the start of the 1/2x28 threads so that person thought of the issue. But on the other one it was less than half that so for sure that one you need the thread protector mounted.
All FWIW>

I've found the first bit of suppressed shooting carbons them up pretty good and it's a non-issue. If you're not going to thread a can on anyway (and why bother when tri-lug is an option?), there's nothing really wrong with adding some Rocksett.

No problems after I installed an "O" ring.

I am certainly curious how an oring would survive in that environment. Even the most exotic ones that one can easily obtain max out about 450degrees F. and it certainly must be much more than that inside the blast section of a suppressor.

Anyway on this. Going back to running a thread protector. I'm now searching for a 1/2x28 thread suppressor for a PTR HK clone that is really long on the threads. Like its nearly double any thread suppressor I have. Internet searching show nothing that is even remotely long enough to cover the threads completely. ideas?