How were machine guns synchronized to the rotation of the prop? What if you slowed down, I feel like eventually the blade and a round will come in contact.
There are quite a few ways of doing it and some guns didnt take kindly to it, another name for at last some of these systems was "interrupter gear" as with the schematic from Wurger they "synchronised" by stopping the gun firing when a blade was in front of the gun.