People do, indeed, hurl all sorts of metal objects at Superman during the course of the Al Plastino story in Action 183 (Aug. 53).
Superman cannot figure out why so many hoods are doing this, when it clearly has no effect. But they are working for Luthor, who has his own plans.
Luthor has discovered that any metal object that makes contact with Superman gains a microscopic amount of kryptonite. This makes no sense, even by comic book standards.
Nevertheless, it works. Superman collapses, and Luthor puts him on a rocket ship and fires him into space, covered in the kryptonite dust. Dumb plan, Luthor. Superman uses his heat vision to short out the ship, which plunges into the ocean, and the water washes off all the kryptonite.
Congo Bill is no longer a roving insurance investigator, and is back in the African jungles, exploring and having adventures. In this story, by Miller and Smalle, an artist is commissioned to paint a portrait of Congo Bill, and follows him out into the jungle to do so.
The artist’s works keep getting defaced during the nights, and Bill and his men keep getting attacked during the day. By the third time, Bill has figured out that the artist is a phony, he is leaving information for the poachers who want to get rid of Bill, and is defacing his own works to cover his lack of artistic ability.