[5][6][7][8][9] Although optical equipment such as rangefinders and ballistic calculators have largely eliminated manual calculations to determine elevation and windage, the fundamentals of accurate and precise long-range shooting remain essentially the same since the early history of shooting, and the skill and training of the shooter, and the shooter's spotter where applicable, are the primary factors.Accuracy and precision of ammunition and firearms are also still reliant primarily on human factors and attention to detail in the complex process of producing maximum performance.[10] Any given combination of firearm and ammunition will have an associated value, known as the circular error probable (CEP), defined as the radius of a circle whose boundary is expected to contain the impact points of half of the rounds fired.[citation needed] The longest confirmed kill in World War II was by German sniper Matthäus Hetzenauer at 1,100 metres (1,200 yd).[citation needed] After returning to the US, Hathcock helped to establish the Marine Corps Scout Sniper School at Quantico, Virginia.Even after being severely burned during an attack on an Amtrac on which he was riding in his efforts to rescue other Marines, which earned him a Silver Star, and after being diagnosed with multiple sclerosis, Hathcock continued to serve, shoot and instruct.[20] Harrison killed the two Taliban machine gunners with shots that took the 8.59 mm (0.338 inch) rounds almost five seconds to hit their targets, which were 900 m (980 yd) beyond the L115A3 sniper rifle's recommended range.