Lucas is wearing the hat that he wears throughout the series in the opening scene of Sharpshooter. However, in the other scenes, he has a different hat on.
In the second round of shooting, Vernon is called for "four in the center, one just out." In fact, the fifth shot was touching the center ring and according to shooting rules if it touches the center ring, it is considered in the center ring.
Lucas McCain's rifle was modified to fire automatically every time he cocks it. However, in the show, when he cocks it BEFORE a fight, it doesn't fire.
At 4 minutes 9 seconds into the episode, there is a shot of Lucas (Chuck Connors) mounting his horse to ride into town. You can clearly see a line of power poles running along the ridge of the mountains in the distance.
Mark refers to his father as "dad" instead of "pa" in the dining room. "I can shoot my dad's rifle."