I suppose it depends what you want it for, a shield to carry about with you, i.e. a portable bunker, doesn't sound like a good idea as the end scenario is two people stood shield to shield reaching thier markers round to shoot each other at point blank range.
If you just embed it in the ground at the start of the game and leave it there it might as well be a pallet or a pile of tyres, i.e. just another bunker on the field.
I hope those spec ops wannabies aren't shooting full auto - that's against most sites rules and possibly against the law but I know what you mean, someone ramping at you can feel like full auto sometimes. The trick to learn against them is snap shooting, don't come out of the same side or hight of your cover all the time and don't do it in a regular rhythm, you'll probably find they are so busy concentrating on thier stream of fire they'll miss a couple of balls coming back.