The target, JFK in this case was slowly moving away from the shooters position. Based on my understanding of the events, JFK would have presented Oswald with a target that was slowly shrinking while moving slightly upward and to the right in a straight, predictable line.
Oswald had all the time to make the first shot, remember, the clock starts with his first shot. Oswald fires the first shot, reloads and aims just ahead of where he predicts the target will be and fires when the target moves into his sight picture. He repeats the process for the third shot.
"Forward and to the right! Forward and to the right!"
OK seriously, that's where the "inaccurate sights" were throwing the bullets. If LHO knew where the sights were puttimg the bullets, he has a gift - NO CORRECTIONS: Aim where you want the bullets to go, and the motion of JFK's car will take him into them. (the offset was only a couple of inches anyway)