The M21 Sniper Weapon System (SWS) is the semi-automatic sniper rifle adaptation of the popular M14 rifle. It is chambered for the 7.62x51mm NATO cartridge.
The M21 remained the Army's official sniper rifle until 1988, when it was replaced by the bolt-action M24 Sniper Weapon System. The M-21 still remains in service and has seen extensive combat in Iraq and Afghanistan.
The XM25/M25 is an upgraded version of the M21 developed by 10th Special Forces Group's armorers for use by United States Army Special Forces and United States Navy SEALs in the late 1980s. It saw some use in Operation Desert Storm.
In standard military use, the M21/M25 use the same 10- or 20-round box magazines as the other members of the M14 family, and weighs 5.27 kg without the scope. The U.S. military never officially authorized or purchased magazines in any other capacity, although 5 and 10 round magazines are commercially available.
Springfield Armory, Inc. also manufactures variants of its M1A rifle called M21 Tactical Rifle and M25 White Feather Tactical/Carlos Hathcock rifle, which are based upon U.S. Armed Forces' M21 and M25 Sniper Weapons Systems but are slightly different, most notably they are fitted with a Picatinny rail to mount a scope.