I have cleaned my AK a few times that way. Wouldn't recommend it, but in a pinch it will work. Also used the oven to dry them
make sure you clear all ammo before you place in oven though. Saw a revolver that was a casualty of being loaded and in a hot oven. Not a safe thing.
Never cleaned a firearm, but steamed many of fish!
I melted my Glock once in the dishwasher
Just kidding, never done this or known anyone to do this but I've seen plenty of videos on Youtube and the like of people demonstrating it.