The Heckler and Koch G3 is a German delayed blowback selective fire assaultrifle produced in 7.62 mm and 5.56 mm calibres fed from a 20-round box magazine. The rate of fire is selectable between single-shotsemi-automatic and fully automatic at a rate of 600 rounds-per-minute. The muzzle velocity is 800 meters per second and the G3 has an effective range of 400 meters. The G3 has a 450 mm long barrel and is fitted with a post foresight and a rearsight comprising a U battle sight at 100 meters and apertures for 200, 300 and 400 meters. The standard G3 is fitted with a plasticbutt stock and is known as the G3 A3, a retractable butt model is known as the G3 A4. Research G3