Development of the M60 series of tanks began in 1965 after the U.S. Army decided to create an improved version of the M48 “Patton” tank. Built by General Dynamics, the M60 entered service in 1960 but was quickly superseded by the A1 to A3 versions. The A3 was notable for its laser fire-control system and was considered one of the best tanks in the world during its service. The M60A3 was later replaced by the M1 Abrams as the U.S. Army's first line battle tank. Its specifications included a crew of 4, a weight of 57 tons, a range of 310 miles, fuel capacity of 378 gallons, length with gun forward of 371.5 inches, height of 129.17 inches, width of 143 inches, stowage for 63 rounds of main ammunition, a 762 mm M240 machine gun and M85 0.50 calibre anti-aircraft machine gun, an air-cooled Continental 12-cylinder diesel engine rated at 750hp, acceleration from 0 to 20 mph in 15 seconds, maximum speed of 30 mph, cross-country speed of 10 to 12 mph, and obstacle crossing capability of 36-inch vertical barriers and gradients up to 60 percent.