The "Off the Grid" perk is a must against these riot shield weilding idiots, as they all use the radar on their shields which lets them now your exact location, off the grid means they won't be able to pick you up on the mini map, which is much more useful as if they dont know where you are, it makes it easy for you to shoot them in the back if you have a good headset as the perks the use take up most the space which means their not very likely to have dead silence. This method worked much better for me compared using blast shield as it isn't always effective and sometimes you still get killed with 1 c4 or noob tube while using it.