Witnesses confirm a revolver was taken from Oswald.
What witnesses?
Oswald admits he had a gun.
You don’t know what he “admitted”.
There are images of the revolver being carried out of the TT.
You don’t know which revolver is in the images.
Documents that preexist this event link an order
You don’t know when the “documents” were created.
and shipment of the revolver per the same serial number to Oswald's PO Box
You have no evidence of any such shipment.
But the contrarians shout "chain of custody" over and over.
You don’t understand why chain of custody matters. Without it, you can’t demonstrate that CE143 was the same gun handled by McDonald, Carroll, or Hill, or that it was ever in Oswald’s possession, much less had anything to do with Tippit. Wanting to believe it is not sufficient.