It seems like the gun would be able to fire right through the props though.
Should be simple to detect when the bullets would hit a spinning blade and when it would pass through.
Rate of fire would slow down when going through the props though...or at least be a bit irregular.
It can be synchronized, and would be especially easy with turboprops that turn at a constant rpm (blade pitch changes speed). However, the changing geometry of the nacelle/blade position would necessitate a special setup. Beyond my pea-brain but I guess those geniuses at Crane could pull it off.