When the SAS used to shoot through car windows like that, they were wearing goggles and baclavas to protect against the hot brass and splintered glass, ear protection too if available. You fire a rifle inside a car you won't be able to hear much of anything for a while, and brass and glass will be flying everywhere. It looked like they were actually using live rounds on a closed set for a few of those scenes . . . not sure how they could've gotten those effects otherwise.