Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
A gunfighter turned US Marshal goes fishing and invites a man who rides up to eat the fish with him. When the Marshal goes to get his jug of whisky that is chilling in the creek, we hear a rattling sound then see a rattlesnake. The second guy quickly draws his handgun and shoots. Then we see the result - a snake with its head blown off, still shaking its rattle. The Marshal commends the guy for being so good with his gun that he can shoot its head off. The snake target-practice scene is included in the movie to start a conversation about guns and shooting and the stranger who turns out to be a gunfighter who has come to challenge the Marshal's reputation as the fastest gun around.
The first snake we see is one of the worst excuses for a rattlesnake on film I've ever seen. It's a badly painted prop with its tail and head moving unrealistically. It turns out it's the same snake used in the movie Catlow which was made a few years later in 1971. (A screenshot of the snake from Catlow is shown above just below the screenshot from this movie.) The production company for both movies was MGM, so they probably borrowed it for Catlow. Or maybe it's their standard pre-killed rattlesnake shot and I can look forward to seeing it in other MGM westerns. The snake we see after it was supposedly shot is a live rattlesnake, probably a Western Diamond-backed Rattlesnake, that has either been just decapitated, or, more likely, has its head buried in the sand so it looks headless but still shakes its rattle.