I kept dying on this one as well. As soon as you hit the guns the Axis will spawn very quickly. The best thing to do is fire the gun press the - minus button immediatly and then quickly take cover behind the short walls surrounding the gun (not where your team is and next to the gun but outside where the Axis were at the start). The first two guns you take out the Axis will always spawn behind you so take cover on the side opposite the MG42 and heal. Look out for the Axis on the side where the car is and stay on the corners of the walls so they can't hit you. On the third gun they will spawn in front of you (the side where the guns are) so run fast and duck on the opposite side. Just go in and pick them off. Make sure you heal first because you will get hit alot when you are finding cover.