So when is a gun clean?
I consider a gun clean when accuracy is restored and the gun functions reliably. You can clean a gun for 5 or 6 hours and there will still be some small amount of fouling left. Fouling gets into the very smallest metal pores and is hard to remove.
I clean my gun bores until the patches come out light gray and the action functions reliably. It takes me about 15 minutes to clean my Glocks. I soak the barrels with M-Pro 7 gun cleaner for 10 minutes and then patch. Done.
Remember….a absolutely clean barrel will not be accurate. It takes a few fouling shots before most barrels are accurate. Just talk to a bench rest shooter.