on top of the receiver. This is a by-product of the design, where the carry handle serves to protect the charging handle. The AR-15 rifle has a 500 mm (19.75 inches) sight radius. The AR-15 uses an L-type flip, aperture rear sight and it is adjustable with two settings, 0 to 300 meters and 300 to 400 meters. The front sight is a post adjustable for elevation. The rear sight can be adjusted for windage. The sights can be adjusted with a bullet tip or pointed tool. "The (AR-15's) Stoner system provides a very symmetric design that allows straight line movement of the operating components. This allows recoil forces to drive straight to the rear. Instead of connecting or other mechanical parts driving the system, high pressure gas performs this function, reducing the weight of moving parts and the rifle as a whole." The AR-15's straight-line recoil design, where the recoil spring is located in the stock directly behind the action, and serves the dual function of operating spring and recoil buffer. The stock being in line with the bore also reduces muzzle rise, especially during automatic fire. Because recoil does not significantly shift the point of aim, faster follow-up shots are possible and user fatigue is reduced. See also List of ArmaLite rifles List of AR platform cartridges Notes References Further reading --> 1983 National Book Award winner. One of three excerpts from National Defense published in The Atlantic; includes the origin of the Armalite AR-15. Rifles 5.56 mm firearms Assault rifles ArmaLite AR-10 derivatives Colt rifles Gas-operated firearms