text: why does the military say that they replaced the m16 for the m4 when the m16 is in action.? this question not only represents the m16 but follows with many weapons being replaced while they are still seen in action. the army has replaced the m16a2 with the m4, but the marine corps did not; they have adopted the m16a4 as their service rifle.  it is yet another version of the standard m16, but with attachment rails on the hand guards (and other minor changes).  the corps only uses the m4 in limited applications.