[Ron Ramirez]

I prefer to tread safely with the temps.

Hot glue melting temps are 250F to 375F.
The application range for the Polypropylene material is -55 — +105C, which is up to 221F.
So, while I think that it might be OK (did it myself in the beginning without ill effects), I prefer to shield the caps from being immersed in the hot glue. Some contact through gaps in the shielding is OK.

For the same reason I put a paper wrap in the tubular caps' ends when I restuff them.
If anything, it will save you quite a bit of that hot glue

There are two types of hot glue - high temperature and low temperature. The temperatures you quoted are for high temperature hot glue. Low temperature hot glue, which is what I use, typically melts at 130 to 260 degrees F.

Let us therefore agree to disagree on this subject, and leave it at that. Or, as my old friend, Rev. Lowell Mason (RIP) used to say -

"You don't have to agree with me. You have every right to be wrong if you want to be."