At one point in this episode, Barney has a whistle in his mouth. The camera cuts to a close-up shot of Barney and he does not have the whistle in his mouth, but in the next shot, Barney is shown with the whistle in his mouth once again. He is never seen taking it out or putting it back in his mouth.
Andy announce that the first event of the day will be the 50 yard dash, and tells the boys to line up at the starting line. When they do, you can see that it's actually more like a 50 foot dash, instead of a 50 yard dash.
In the first scene, Barney shows his enthusiasm for starting the race and misfires his pistol inside the courthouse. Throughout the series, Barney is known to never have a loaded gun, keeping his sole bullet in his shirt pocket.
Barney uses his service revolver as a starting pistol, as well as firing it in demonstration. He should know better than to discharge a live round into the air, as someone could get killed when the bullet comes down.