M14s have been used extensively in the Army (see link) since the beginning of current conflicts.
They are also in use by Navy and Marines.
http://www.armytimes.com/news/2010/03/army_m14_032210w/
Over the past 5-6 years I have seen a few articles about the ineffective stopping power of the 5.56mm round. I remember one where troops stated it was taking 2-3 rounds to put down the jihadis. Also remember another where some Special Ops troops were being taught to shoot at lower abdomen rather than center mass to increase chance of stopping their target quickly by hitting a hip or major artery.
I’ve used the M16,the only effective shot to an enemy would be to the head.Of course at close range the M16 will effectively shred an opponent,but if the SHTF I’m carrying my HK 91.(and my 1911,screw those 9mm pussy pistols)