Spector,
I had an old (TePeCo, I think it was) chronograph in the 70's that required a 5' screen spacing. The screen sensors were mounted on a piece of steel angle to which I added some pieces of heavy steel angle "bullet deflector shields" in front of the sensors. They were intended to deflect mainly handgun bullets, since a center fire rifle hit would have blasted on through. They did indeed save the sensors on more than one occasion, but usually wrecked the plastic sun shade (but this was easy to replace since I made them out of translucent (milky) plastic sheet.
Sabots, wads, and patches from muzzle loaders and other toys can be real hard on chrono's too. Even blobs of lube and unburned powder granules can be rough on displays and screens. My .45-3 1/4 (.45-120) Sharps replica is a real chrono blaster with 130 grains of FFg black powder, fiber wad, and a 540 grain cast bullet with plenty of my Bore Butter/Beeswax lube concoction!
JL,
That's why I rather like the Chrony with the remote display/electronics - it doesn't get blasted with debris.