America's Army 3

In America's Army 3, Every Detail Counts™ and as a result, the game has more authentic military elements including training, technology, weapons, and audio than any other military game.

Built on Unreal Engine 3, AA3 delivers stunningly realistic environments, lighting effects, animations, and team-based experiences so that America's Army players can experience how Soldiers train, live, and advance in the Army. Players are bound by Rules of Engagement (ROE) and gain experience as they navigate challenges in team-based, multiplayer, force-on-force operations. In the game, a player's actions and demonstrated Army values are integral to successful mission accomplishment and affect a player's career progression.

To play, simply download and install the Deploy Client, then run it to download the full game.

Free Full PC Game Download (deploy client - 226 KB):
Official link
GamersHell