I keep my firearms clean, including the bores. But, I don't over clean the bore. I usually run a wet patch, a dry patch, another wet patch, and one more dry patch and call it good.

Oh, and in case your buddy doesn't know any better, one of the worst things you can do is coat the bore with oil and then fire a shot. If he chooses to store the rifle with an oiled barrel, make sure he runs a dry patch through it before he takes it out to fire it.