You are mighty lucky to have a place to practice this kind of stuff.
No range in our area would allow this kind of live fire practice, so airsoft is all that's available.
If the car isn't obstructed, and it probably won't be if the carjacker wants a quick getaway, what's wrong with just flooring the accelerator and scooting away?
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”