5 Against the House (1955)

Four college buddies enjoying a night at a Reno casino are told by a cop that robbing the casino "cannot be done." That gets the brainiest rich kid among them thinking up a plan for the perfect robbery. He convinces the others to join in when they hear that it will only be a college hoax, his plan being to let the police know where the money is afterwards. The thing is, one of his friends has a head injury from the war, and has no intention of returning a dime.