> What is the non-conspiracy explanation for the magic bullet involved in the JFK assassination? I only know the conspiracy theory that claims that the CIA accidentally shot JFK and then covered their tracks.

It's entirely possible that a secret service agent accidentally shot Kennedy, and they're on the record of saying so.

"We don't know" is not really a conspiracy theory. "We don't know, therefore X must have done it" is a conspiracy theory. Conspiracy thinking is the tendency to make these connections.