It all depends on which branch of the Army has what. I personnaly have seen many Knights handgaurd systems and "Swan Sleeves" issued that have a few mods. on the rail system that civies cannot get though. In optics I have seen Aimpoints, Trijicons, & C-Mores not to mention a few others that I do not recognize that are all issue. But as I understand it the Aimpoint is most issued/prevalent. My Infantry buddy just mounted his on the reciever rail of his M-4 if I remember correctly.