It can be useful, but only once you have the necessary amount of firearms and ammunition. Assuming you do, not very useful except for shtf and actual battle. I disagree though about too heavy. A light weight carrier and a helmet-properly fitted they can be helpful even without being shot or catching shrapnel. I once had this whole wall, complete with sea wire, fall on me. The Armour was helpful. Granted, you could get the same effect with a hard hat, but still.