I seem to usually have problems getting the holes lined up perfectly straight  for when I go to drill my receiver to match up with the factory holes in the trunions. I wonder on my next build if i can just cut the rivets down to where they are flush on my trunions  then  put the trunion into the receiver then into the vise for the drill press and drill  my own holes through the receiver and trunion instead of using the factory holes? that way it would all line up right the first time.