Hi:
Like Herbert, I prefer not to use Red to avoid the heat aspect, but two very respected gunsmiths that have at least 100 years of using their ingenuity prefer Red, not blue for this sort of fix..
For what it's worth, one of them used that fix when one of HIS very expensive rifles was returned with a noticeably loose barrel.
I saw it loose and later tightened. In fairness, it was approximately 15 years old and had been through several owners.
It may originally have been a "switch-barrel" rifle. A few were made that way.
We were surprised the 'smith that made it fixed it over night while at a gun show away from his shop and tools.
He wouldn't say how he did it, but it was soooo tight the next morning. He had it less than 18 hours.
A few months later an unrelated second 'smith shared his use of Red for liners, etc and I made a note of its product number.
I then politely asked the other 'smith if he had used Red #xxx. He smiled and said " that will work".
That was almost two years ago. Owner remains very pleased and no charge.
I have seen rosin used as a sealant on Kar 98 barrel threads, especially G33/40's.
When that "joint" FINALLY SNAPS loose, it does so with a loud, sharp "crack" and often a puff of smoke.
So I guess "thread SEALER", like most things is not new. Germans smmaaarrrtt.
Maybe you should call LOCTITE first, just to get their help on temperature.
Most Epoxy seriously degrades at as little as 150F and is useless at 400F.
But that applies to two-part stuff, which RED is NOT.
See ya, Kevin