If you’re impatient & don’t have a deep freezer there’s always keyboard cleaner spray. Don’t freeze it inside & breath that. And I’d also try PB Blaster or WD40, Slick 50 One, let it soak. Work it back on first as if it’s stuck at a certain point it may slip off way easier once fully on, indexed free spinning & find a rotation where it slides off unhindered, if there is a spot.
Anything that requires a hammer on precision equipment gets me questioning my actions. I don’t have proper equipment to break free barrels, brakes, shotgun tube fed magazines, etc. & it can be a real SOB to impossible without it.
Grub screws? Backed out completely? A burr?