Nothing would have happened because, if the barrel is a turn too far in, closing the bolt is an absolute impossibility. If the barrel is turned in just a little too much, closure would be difficult and, if it could be closed, there would be no issues with firing. If the barrel is out a little far, an excessive headspace condition would exist which could be dangerous. If the barrel was out by one full turn, headspace would be grossly excessive. In this case it is possible the rifle wouldn't even fire but, if it did, a case head separation would undoubtedly occur. Look, the gunsmith did make a mistake and it's difficult to understand how or why but I expect he will correct it. I won't comment on the punch marks except to say that I don't see the point. On a Savage, the lug is located by a notch in the receiver and cannot turn. How much the nut is turned does not affect headspace.