You do want some kind of protection for your chrono. I was shooting some 200 shockwaves once before figuring that out and even at 15 feet from the muzzle one of the sabots dropped into the open top of my F1 master with enough force to put a hole in the plastic housing of the rear detector. The detector still works but the broken plastic had to be removed because it was blocking the eye. After that I decided to put some protection over it.