I was always taught that a new gun can have metal particles from the manufacture. I was told by a guy in the know, that when guns are assembled and oiled at the factory, metal particles in the air adhere to the oil, since it's lubed up on the spot. Supposedly that metal can work its way into the barrel and scratch up the inside. My diesel engineering professor does the same thing with brand new cars. He makes the dealership change the oil before he drives it off the lot. Says that metal from the manufacturing makes its way into the oil and scuffs cylinder liners.
Don't know, nor do I care if it's true. Cleaning a gun should be part and parcel of thoroughly inspecting a firearm for defects and proper craftsmanship, before you fire it. I don't trust my face, or my eyes to some monkey on the manufacturing floor.
Also, Now that I'm a froglube fan, I want to strip the oils and cleaning solvents out first, so I can use my froglube.