Jareth saw Mira take cover, he kept his steady fire from his rifle. Eatting away on her cover and crumble it slowly from other side but it will take more than he has bullets collapse it down. But at least Mira keeps low. He saw the three missile launch towards him! His turret aims and fixes upon first one, rapid firing it fires first missile off into pieces. Second was closer and exploded! The third almost hit on Jareth but turret fired and succeed destroy it but it was hair's trigger from missile hitting Jareth and instead Jareth got merely after burns from said missile, which scorched his armor but left no damage on him otherwise. So it seems turret works against three missiles tops, fourth and other missiles hitting in if Mira launches more than three at once.