The CIWS is designed to be the last line of defense against antiship missiles. Due to its design criteria, its effective range is very short relative to the range of modern ASMs, from 1 to 5 nautical miles (2 to 9 km). The gun mount moves at a very high speed and with great precision.

• Top 10 Close In Weapon Systems In The World.
• Rheinmetall Oerlikon Millennium Gun (CIWS System )
• Denel 35 millimeter dual-purpose gun (CIWS System )
• Meroka (CIWS System )
• Sea Zenith (CIWS System )
• AK-630 (CIWS System )
• Goalkeeper (CIWS System )
• Phalanx (CIWS System )

0.787 inches
All 20 mm cartridges have an outside projectile (bullet) diameter and barrel bore diameter of 0.787 inches (20.0 mm). These projectiles are typically 75 to 127 mm (3–5 in) long, cartridge cases are typically 75 to 152 mm (3–6 in) long, and most are shells, with an explosive payload and detonating fuze.

30mm
The A-10 Warthog’s massive 30mm cannon, the GAU-8/A Avenger, is one of the most iconic weapons ever designed and is as famous as the plane that carries it into battle.

phalanx, in military science, tactical formation consisting of a block of heavily armed infantry standing shoulder to shoulder in files several ranks deep. Fully developed by the ancient Greeks, it survived in modified form into the gunpowder era and is viewed today as the beginning of European military development.

Each C-RAM system costs somewhere in the region of $10 to $15 million depending on the final spec of the units purchased.

The Goalkeeper system has the advantage of heavier rounds and almost twice the effective range of the original Phalanx, able to break up an incoming missile further way from the ship. The through-life costs of the larger Dutch system were higher as it was deck-penetrating, limiting which vessels could carry the mount.

12.7 mm
Metric and US customary

Like most cannon ammunition, 20mm caliber weapons are typically used against large targets such as vehicles, buildings, or aircraft. Though lethal against individual soldiers, 20mm ammunition is so large and heavy that its effects are inefficiently utilized on such relatively small targets.

The US does not sell military aircraft to civilians and no other country has A-10s, so no, you cannot purchase one.

Each system consists of a modified Phalanx 1B CIWS, powered by an attached generator and mounted on a trailer for mobility. Including the same 20 mm M61A1 Gatling gun, the unit is likewise capable of firing 4,500 20–mm rounds per minute.

The Phalanx CIWS Block 1B mounted on the Oliver Hazard Perry -class frigate USS Elrod, in mothballs at the Philadelphia Navy Yard. The Phalanx prototype on USS King in 1973. Rounds from a Mk-15 Phalanx CIWS from the guided missile destroyer USS Mitscher hit ex-USNS Saturn during a sinking exercise (SINKEX), 2010.

The Phalanx CIWS (pronounced “sea-wiz”) is a close-in weapon system for defense against airborne threats such as anti-ship missiles and helicopters.

A technician checks the radar transmitter and microwave assemblies of a Phalanx CIWS, most likely a Block 0. On the unit in the background, the search radar can be seen at the top left with the vertical, orange-peel shaped, tracking radar below it.