For those in need there is a way that can work, although it might cost you a bit of ammo.
When in the chapters with the zulu like majini, get onto a high platform with only one point of entry for the majini. Get out your machine gun. Look over the edge and see how far they are from jumping up. When you think their close to jumping, move back from the edge and start firing in the middle where they will jump. They will then jump right into your line of fire.
Easy stuff. Good luck guys!