One print is enough to associate Oswald with the rifle. The prisons are full of criminals who left one print, hair, or drop of blood at a crime scene. And Oswald's prints were also found on the SN boxes and bag. If the FBI and DPD were involved in framing Oswald, they would have confirmed more prints on the rifle whether they were there or not. If this tells us anything it is that they were not attempting to frame Oswald and his prints were found on these items. I don't believe Oswald wore gloves during the assassination because he was smart enough to know it didn't matter, but who knows. Using 1963 technology, it is entirely possible that few prints would show up on the rifle and maybe Oswald had wiped it down the night before. Suggesting that in someone's subjective opinion that there should have been more prints found is not persuasive of anything.