The Navy’s USS Boxer has a Phalanx Close In Weapon System (CIWS). It is nicknamed R2-D2 for its similar dome shaped top and automatic nature. Actually if you watch the video below, the supports are somewhat shaped like R2-D2 legs. Watch the tower pivot and spin. It really resembles an R2 Astromech droid. Just with a large gun protruding from the crotch.
The Phalanx fires a mere 4,500 rounds per minute which equates to 75 rds per sec.
It fires a 20mm round at 3,600 fps.