The secret service accidentally killed JFK after the magic bullet. It explains the unlikely 4 shots from Oswald. It explains why the kill shot acted differently than the magic bullet. It explains why there were reports of the smell of gun smoke on the ground.

But most importantly it explains how the conspiracy could actually be kept a secret. If a secret service gun delivered the killing shot and that became public knowledge, the secret service wouldn't exist today. It's a fuck up so collosal it actually has the potential to keep everyone's mouths shut. It would have been an even greater embarrassment on the world stage at the absolute peak of tension in the cold war.

I could see a bunch of government men in shady rooms agreeing to keep the secret, the president was already shot. He probably would have died already from his wounds. Oswald was technically correct when he called himself a Patsy.