Could someone hit jfk riding in an open car if they were shooting from a sewer grate at curb level?
From the book repository he, the shooter, is tracking a moving target moving... (trying to recall various TV programs about it) kinda left to right, away from him and moving not as fast as a car in traffic, but fast enough that he has to compensate for it AND in Oswald's case operate the bolt-action Italian war surplus Carcano rifle he was supposedly armed with. (IMHO a throw-away; a weapon to be given to a "fall guy". Going price at the time was about $30 cash and carry...)
The guy in the sewer has more of a straight-on shot once JFK comes unfortunately into view. For a skilled shooter, one shot and it's done.
Unfortunately, and JMHO. YMMV.