It performs better than M855, I think most can agree on that- but is it worth the trade off of damaging / wearing out weapons at a much faster rate? I'm with TehLlama on just using Mk318, but of course the Army won't because that actually makes sense.

As a side note, this is yet another reason my AR500 armor is a bad idea. When M855A1 becomes common to stateside units, inevitably rounds will be "acquired" and make their way into private hands.