How does the switch in narration from third to first person highlight Dave's obsession with the gun at the end of the story?
The whole story is told in third person omniscient, meaning that the narrator can see into Dave's thoughts. What you think is first person is actually interior monologue, a narrative device where a character's thoughts are made known to the readers without the use of quotation marks. In first-person narration, the narrator is telling the story, but in this instance, Dave is not aware that his thoughts are being used to tell the story. The third-person narrator's ability to get inside Dave's head allows the readers to know exactly what Dave is thinking, and the reader gets Dave's thoughts exactly as he is thinking them. This is why Dave's thoughts are written in the dialect of black Southern farm workers.
The use of the interior monologue does highlight Dave's obsesssion with the gun at the end of the story because the reader knows how important the gun is to Dave. He equates power and manhood with the gun, and through his thoughts, we understand this.