I hate to correct you but Oswald was a Marine. You are also right about his marksmanship. From a distance of 250 yards he hit 246 bulls eyes out if 250 shots with open sights. The longest shot from the bookstore to Kennedy was 82 yards. He used a 6.5 mm bolt action Carcano with a scope.
I stand corrected. As I’ve posted here, the Frontline doc supports your information about Oswald’s ability. He easily, with a telescopic site, could have knocked off the shots that he did, in the 6 or 7 seconds, (an eternity really) that he had. In fact, Frontline re inacts it.