M-16

U.S. military's proud gas operated, air cooled, light weight, hand held piece of shit. It is very sensitive to all elements that you'd find outdoors, including air and sunshine. It jams if fly shit gets into the bolt so essentially it's not much of a infantry weapon. It must be cleaned constantly to be able to fire a full magazine, and after that it needs more maintanence. To extend a grunt's life on the battlefield, the A2 variant isn't fully automatic, so there will be some time between dissasembly and cleaning. The reason it became standard issue in the U.S. military is because in the 1960's Colt executives bought some high ranking military brass a few beers and lapdances. Other than that, there's no reason why a recognized military would adopt such garbage.