If I understand you Walt you feel that Mauser was never found first? I have no opinion though I now there was a picture of the original gun that was being called a Mauser. I assume that photograph can be shown to be off the MC?
The second part is not really addressed to you, but if the rifle was found neatly tucked in the opposite corner of the sixth floor from the SN doesn't that increase the time it would have taken Oswald to get to the lunchroom?