So, why didn't Dallas Police report sniffing the muzzle of the 6th floor rifle and that of Oswald's revolver to determine if either had been recently fired? Wasn't the sniff test used in those days?
And why didn't they report finding shooting residue inside Oswald's revolver? Shouldn't there have been some soot if he had recently fired it several times? Here is a picture of a dirty cylinder.
Here is another one with a heavier layer of soot.
So, what did they see when they opened Oswald's revolver?