The SR-25 (Stoner Rifle-25) is a semi-automatic special application sniper rifle designed by Eugene Stoner and manufactured by Knight's Armament Company.The SR-25 uses a rotating bolt and a direct impingement gas system. It is loosely based on Stoner's AR-10, rebuilt in its original 7.62×51mm NATO caliber. Up to 60% of parts of the SR-25 are interchangeable with the AR-15 and M16—everything but the upper and lower receivers, the hammer, the barrel assembly and the bolt carrier group.