Short range: the maximum effective range of 20 mm (0.79 in) gun systems is about 4,500 metres (14,800 ft); systems with lighter projectiles have even shorter range. The expected real-world kill-distance of an incoming anti-ship missile is about 500 m (1,600 ft) or less,[4] still close enough to cause damage to the ship's sensor or communication arrays, or to wound or kill exposed personnel. Limited kill probability: even if the missile is hit and damaged, this may not be enough to destroy it entirely or to alter its course enough to prevent the missile, or fragments from it, from hitting its intended target, particularly as the interception distance is short.