Wooden dowels will prevent the electronics from getting all frazzled like a bullet will do by hitting the metal rods. The instructions on my Chrony even mention this option.
However, I abandoned the idea of using dowels after seeing how they provide poor support in a 10-15 MPH breeze and cause the diffusers to shake like crazy.
I don't know what the rods look like for a Chrony, but my chronograph "lost" one of the rods too. Mine were 3/16" diameter, so I went to home depot and bought a section of 3/16" steel rod and cut it into pieces the same length as the originals. Now I have two spares in case I shoot.... err, I mean "lose" another rod.
The softer the rods are when you shoot them (notice I didn't say if you hit them) the less potential exists for transmitting damage down the rod and into the chrono itself. Aluminum welding fill rod or solid aluminum clothesline approximate the rods that came with my Chronys. The softer the better!