Ah, if the outlaw is hanging on, then he/she/it is stationary relative to you in the car.
I certainly have no objection to folks learning how to do this, but the likelihood of ever needing this is someplace far to the right of the decimal point.
As to shooting someone in the back, this has come up where the outlaw is starting to turn away, or reacting to a prior hit (bending over, starting to spin) when hit again.
And rifles have a place in self defense, depending on ... your place (pun intended). I live way out in the country. Someone could decide rather than risk a home invasion, they will just snipe me from a distance, and then move in. I am prepared to shoot back - and yes, it has happened in the outback.