I took my Bushmaster 16" to a smith to have the Bushmaster AK style compensator pinned on.
When I arrived to pick up the rifle, the smith had silver soldered the comp on. No pin was used.
Will this damage the barrel or liner?
While I am not a gunsmith, or a metallurgist,
I do know that silver-soldering is one of the BATF approved ways of permanently attaching a compensator to a post-ban barrel.
Your barrel should be just fine assuming your smith is competent.