No, not kidding. I do remember the day/event of his death. I do recall the video (film) of a guy demonstrating how the rifle worked and trying to put rounds on a target in the same time frame, same range. The ‘sharpshooter’ couldn’t do it. As I recall, the story was more about amazement of how Oswald could have managed to do it as an untrained shooter, not so much as a conspiracy thing. Honestly I don’t even remember now if the rifle had iron sights (I think it did) or a scope. I just remember the perception of the moment — that maybe it wasn’t him with that rifle. I don’t really participate in the whole who shot Kennedy thing. I also have probably more doubts than beliefs that Oswald was a lone nut who got lucky. But I can move on ;-)
While he wasn't an outstanding marksman in the service he was a Marine and there's no Marine that's an untrained shooter.
I would also observe that having seen the setting in person I've never seen a video or a photograph that accurately represents how close in everything is. As an average marksman my first thought was "with a round chambered I could do that". True I've never fired a Mannlicher-Carcano but I just don't see it being as hard as some have portrayed it.