This is a close-up of the gun barrels on one the USS Iowa's four Mk.15 Phalanx AA Gun mockups. I've described this weapon in some detail in earlier posts, but there were a few details I left-out until now.

First, the Phalanx is basically a naval AA Gun version of the M61 Vulcan aircraft cannon, but it has a different rate-of-fire; while the Vulcan fires at 3000 rounds/min or 6000 rounds/min (it depends on the model and/or setting), the Phalanx fires at a more unusual 4500 rounds/min. I'm not sure why this is, but as you saw in the video I linked to the description of the earlier photo, it's plenty fast.

Second, this is what is known as an "Externally-Motivated" weapon. Unlike many other autocannons, the Vulcan and Phalanx are not operated by any of the forces exerted by the rounds being fired; everything is driven by electric motors and servos. The good news is that this allows the high rates of fire previously-described; the bad news is a high power-drain, and no ability to fire the weapon without power.

Third, though some models of the Phalanx can be overridden, so they can be aimed and fired manually, they are otherwise completely automated. They're designed to instantly respond to any air contacts the targeting system considers a threat, and engage and destroy the target if all the "warning signs" are apparent. It does this all by itself; the Phalanx is judge, jury, and executioner... and it *alone* decides who lives and who dies.

Fourth, there is also a towed, land-based Vulcan AA Gun (the M167 VADS --- "Vulcan Air Defense System"), and a self-propelled version in a turret, usually mounted atop a converted M113 Gavin APC chassis (this specific vehicle is called the M163 VADS). These land-based guns have several selectable fire rates, as high as a continuous 6000rpm, or as low as an artificially-short burst at 3000rpm. I'm not sure if the VADS guns ever shot anything down, but they're terrifyingly effective against surface targets; in the Vietnam War, the US military used them against massed enemy infantry!

Finally, the Phalanx has a number of technical issues, in addition to an Angel of Death Complex. When the USS Stark came under missile attack in 1987, the Phalanx failed to defeat a pair of incoming Exocet missiles as advertised --- in fact, it never even activated. Another issue is that popping chaff in close proximity to a Phalanx can cause the weapon to think that the resulting large radar contact is a threat. This happened in combat during the Persian Gulf War, in which chaff launched by the USS Missouri caught the attention of the Phalanx on the USS Jarrett, which opened fire on the chaff --- and showered the "Mighty Mo" with 20mm shells! It's fortunate the Missouri was an armored Battleship, because a hail of fire would have shredded anything else active in the US Navy at the time;
http://www.gulflink.osd.mil/du_ii/du_ii_tabh.htm

Also, here's a bit of weird irony in that incident. The Jarret (whose Phalanx was decidedly hyperactive) was a sister ship of the Stark --- while the Missouri is a sister ship of the Iowa!