Someone will have to show me a fire started by shooting anything normal into dry grass.
After about 35 years involving deserts, handguns, and rifles; I've seen dirt, rock chips, wood chips, and sometimes nothing at all but never a fire.
You can make sparks hitting a steel plate, I presume a derelict car body could make sparks as well, but I'd also guess it would take a miracle for either one to light the of driest kindling.
(That said; any responsible target shooter will predetermine that his or her backstop is safe, for the shooter, for other people, and for any natural risks. And, I've never heard of a fire started by a hunter pulling the trigger on Bambi.)
Only with steel-core military surplus ammo. That is now as scarce as the tracer and incendiary rounds - statistically unlikely to cause any fires.