You ever fought, silentounce? I mean, really fought, in inter-personal combat? (Not gunfights. I can't comment on them.)
I have, not for sport, or the army, but to save my hide. I've taken cuts to the arms and body from knives, and blows from fists and clubs. (I was a foolish teenager

)
The 4e mechanics model all of that quite well. Its 1-shot, that gets through your defences, to take you out. You're healing surges are either physically restorative, trigger an adrenal rush, or model your own capacity to dig deeper, when needed. But you can only do it so often, and it really takes it out of you. But given a chance to rest, you can go back in.
I fought, once, with two broken fingers, and a cut to the bone on my right forearm (That had been bandaged.)
Whether that 1 shot is because you're slipping, and tired. (Extended PC/NPC Battle) Because you're totally outmatched (Minion vs PC/NPC) or because you've taken several beatings already (Out of surges.)
I, personally, feel that the whole system will fail badly when it comes to DnD Modern. Modelling a rifle shot is a lot harder.
The problem still exists with a crossbow, but the momentum, would, I imagine, be a lot higher.. at least from a rifle. Anyway. The end result is, the system is internally consistent.