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someone mentioned they ran into one that they had used some kind of past on the threads that was heated and welded the threads of the MD, that one I have not seen yet
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That would be a silver solder installation - comes off with just heat, but takes a lot of it, as in MD glowing medium red to yellow, depending on the high-temp silver solder alloy used.
If the pin was actually brazed (not a lawful installation method per ATF, so far as I know), then there was filler flow all around the pin, and possibly down into the threads anywhere the metal was hot enough for the filler to stick.
Whenever I've not been sure of the installation method, I'd either:
1) chuck the barrel into my lathe, and take short passes around the base of the muzzle device until the pin(s) dropped free; or
2) split the muzzle device with a bandsaw and then grinder or dremel until I could crack it off in two halves with a chisel.