He said most Marines qualify "expert" and most of the rest just under.
It is possible that Oswald acted alone but he would have had to have been extremely lucky to have made the shots he made.
I was once champion of my gun club, and I think I would have had difficulty making those shots that fast on a moving target that small from that distance. Still it is within the realm of possiblility.
You ever been to Dealey Plaza? I have. It is a much smaller area than it appears on film. Much smaller. The grassy knoll that looks so far away on the Zapruder film is like right on top of you. The JFK limo was 265 feet from the Depository window at the moment of the last shot, the head shot. Less than 100 yards. Oswald had a rifle with a 4X scope. The car was moving at 11 miles an hour when it turned the curve, and according to witnesses slowed down as the shots were fired, and was completely exposed. This was not as hard a shot as people make it out to be. And the thing is, the fact that Oswald even qualified at all as a Marine rifleman makes him better than Joe Schmoe coming off the street and trying to do this. FYI, I was a conspiracy buff as a youngster, but reading Posner's book and actually visiting Dealey Plaza and seeing the area and putting 2+2 together in my mind made me do a complete 180 on it.
Actually Oswald was an UNQ or an unqualified rifleman, he later just barely made marksman. He was a lousy shot.
My husband was on the Navy Rifle Team and taught shooting in the Navy -- he has always said: no way!