M21 is a Vietnam era sniper system. What Davis has is a regular grade M14. A quantity of them have been supplied to the Stryker units for designated marksmen. The only modification is a rails system for mounting optics and other ancillary devices.
They were also given special training using a contract instructor who is an expert combat shot (and retired officer). Sgt Davis attended this training last year.
d.o.l.
Criminal Number 18F
As for the M-21 system, I am not showing my age. I am young, YOUNG I tells ya! Just a little behind the times is all...