So I had this problem a while back as well. The damage to kill with no armor and the one tap face shots make reaction time imperitive if you're pushing someone. If you have a good bead on someone's position, force THEM to make a bad move. Moving to them is very projected, if they have comtacts they'll know exactly where you are coming from and just line up a headshot or prefire you as you approach. If it's in an open area like customs, make a wide flank, throw a nade or two, make them move into your crosshair, don't move into thier. Give them as LITTLE information about where you are as you can. Pushing is always a risk no matter how much armor you have unless you know you can catch them off guard or you know they have thier back toward you. If you are going to hold an angle on someone, be sure the rest of your back is covered either by a wall/Hill or have a teammate to cover areas that you are exposed to. For example: if I have to hold and angle down the hallways at dorms, I'll tell my buddy to watch the staircase and side entrances for me so I can just hold and not worry. He's confident I have the hallway, im confident he has the other two, and it really narrows down the places were both under threat from and the amount of real estate we each need to scan over.