Oswald's shooting was good but not what I would consider remarkable. As far as the distance goes, it was an easy shot. The only real challenge was getting off accurate multiple shots in the given time. The rifle he used was fairly accurate, but the operation of a bolt action rifle makes target acquisition a bit problematic when firing rapidly. However with practice a competent shooter can pull that off without too much trouble. The people who make the claim that Oswald's shots were impossible are obviously not experienced with rifles. And Oswald was a Marine. Even a bad shot by Marine Corps standards is still a damn good rifleman.

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Be very, very careful what you put into that head, because you will never, ever get it out. ---Cardinal Wolsey (1475-1530)