Actually it's really not strange. Oswald's revolver was also originally equipped with a 5" barrel which was shortened to 2¼", most likely for ease of concealment. While this combination of factors made a conventional ballistic fingerprint unattainable, the test results were consistent with what would be expected from such a revolver. This minor issue amounts to a red herring, as multiple eyewitnesses were present at the incident and positively identified Oswald as Tippit's killer.