when you start in the barn, call in an airstrike (dont forget you have these) on the field in front of you , after that go to the shed on your right and light up some more people coming in on the right side of the level. i said it easier then it is cuz veteran is a bitch but that wasnt even my hardest level.
you gotta keep movin forward though or theyll just keep coming....also popping in and out of your scope fast is a good strategy , easier to lock on to the targets