I had my revolver refinished with Cerakote. The internal parts were also refinished, including the cylinder chambers
The Cerakote process can be tricky to do correctly
The problem is that the process closes tolerances by a couple thousanths of an inch. Sometimes that's not a problem, and sometimes it could be a good thing. For example, Cerakoting the slide and frame of a semiauto might improve fit a bit.
The problem with revolvers is that you've got a bunch of tiny parts that fit really tightly to begin with. To do the process right
, the gun should be disassembled, the small internals should be set aside, and the insides need to be polished after the coating is applied. If these steps are skipped, you end up with a revolver that fits too tightly, and with a great deal of excess friction between parts. Imagine spray-painting the inside of a watch without removing the cogs and such, and you've got the idea.