I’m seeing all kinds of opinions on what it takes to permanently attach a muzzle device to a barrel. There are all kinds of theories floating around the internet, but the ATF is unambiguous and anything other than what is stipulated below is a foul.
Please note that Rocksett, Red Loctite, Gorilla Glue or JB Weld does not meet this criteria!
Permanent methods of attachment include full-fusion gas or electric steel-seam welding, high-temperature (1100°F) silver soldering, or blind pinning with the pin head welded over.
Ref: ATF 5320-8 ATF National Firearms Act Handbook, pg. 5.