What does the military use these 5.56 rounds for i amagine shooting at vehicals and threw heavy cover. and how do they work on stopping people not wearing body armor?

How does a person get to 463 posts without noticing that there is a forum dedicated to ammunition, that there is a link to an excellent ammuntion FAQ that covers these questions, and that this question is often discussed around here?

At any rate, M855 is the standard ammo for the M16A2, M16A3, M16A4, M4, M4A1, M249, and any other 5.56mm weapon that doesn't have the old 1/12 twist rate.  It is used for anything and everything that those weapons are ever used for.  M855 has more or less the same terminal performance as the older M193 ammunition.