Problem is, contrary to popular belief, it isn’t difficult to learn how to shoot a rifle. “Beware the man with only one gun, for you may be sure he knows how to shoot it. A buddy of mine found an old rifle in a dumpster when he was a kid, a POS, bent barrel etc. He was a crack shot with that thing.
Oswald was graduated from the United States Marine Corps in 1957. They taught them how to shoot in those days. All of the armed services take thousands of recruits, many of whom have never fired a gun in their life, and within a few hours have them knocking down man sized targets at 600 meters. I’m not arguing they are great shots but they are putting them right in there. He took the time to zero the Carcano, that much is known, and the witness accounts suggest the limousine slowed to a crawl or even stopped in the road at one point.