I've never used GunKote on a gun, yet. However I have used it on quite a few motorcycle engines. It resulted in measureably cooler oil temps in the air cooled motors.
Also, where something aluminum rubbed against the GunKote finish, no damage to the finish happened; but something steel rubbing will eventually wear through the finish.
It is darn good stuff.
This spring I'll be experimenting with KG GearKote on moving firearms parts.