Advanced Gun System

The Advanced Gun System is a naval gun system under development by BAE Systems Armaments Systems (formerly United Defense) for the Zumwalt-class destroyer of the United States Navy. Production has started; the first magazine was delivered to the U.S. Navy on 25 May 2010.

Originally designed for mounting as a vertical gun, this 155 mm (6.1") caliber gun has since been slated for mounting within a more conventional turret arrangement. The AGS is designed to offer a weapon system capable of delivering precision munitions at a high rate of fire and at over-the-horizon ranges.  As a vertical gun system it would only have been capable of firing guided munitions; the turret mounting will allow the use of unguided munitions as well.

Description
The AGS uses the same 155 mm caliber as most American field artillery forces, although it is unable to fire the same ammunition. Instead, a new range of ammunition is under development for this weapon. The gun barrel is 62 calibers long, and is able to fire the entire magazine (300+ rounds) with an average rate of fire of ten rounds per minute using a water cooled barrel. The AGS is to be mounted in a turret specifically designed for the Zumwalt class destroyer with fully automated ammunition supply and operation. The turret itself is designed to be stealthy, allowing for the entire length of the barrel to be enclosed within the turret housing when not firing.

Ammunition
The development of new ammunition for the AGS under the name Long Range Land Attack Projectile (LRLAP) is one of the major advances offered by the AGS program. The munitions are to be highly accurate, with a circular error probability of 50 m or less. Lockheed-Martin conducted a flight test of the munition in July 2005, reporting a flight distance of 59 nmi.

The LRLAP ammunition features separate projectile and propellant portions. Total weight is 225 lb, including a bursting charge of 24 lb. The maximum length of the combined munition is 88 in, amounting to about 14 calibers.

Operation
A primary advantage of the AGS over the existing Mark 45 5" gun which equips most major surface combatants of the US Navy is its increased capability for supporting ground forces and striking land targets. With a 10 round per minute capacity, it offers the ability to deliver firepower close to that of a battery of six 155 mm howitzers.  This will increase the utility of vessels equipped with the weapon, especially in areas in which the US Navy exercises absolute sea supremacy.

Usage
The AGS is currently only slated for inclusion on the Zumwalt class destroyer although it could also be included in other future ship designs. No plans have been revealed to retrofit it to current ship designs. The shortening of Zumwalt procurement to three ships increases the likelihood that BAE will attempt to market AGS to other programs.

History
There has been research on extending the range of naval gunfire for many years. Gerald Bull and Naval Ordnance Station Indian Head tested an 11 inch sub-calibre saboted long-range round in a stretched 16"/45 Mark 6 battleship gun in 1967. The Advanced Gun Weapon System Technology Program (AGWSTP) evaluated a similar projectile with longer range in the 1980s. After the battleships were decommissioned in 1992, the AGWSTP became a 5" gun with an intended range of 180 km, which then led to the Vertical Gun for Advanced Ships (VGAS). The original DD-21 was designed around this "vertical gun", but the project ran into serious technology/cost problems and was radically scaled back to a more conventional 6.1 inch Advanced Gun System (AGS). One advantage of this move was that the gun was no longer restricted to guided munitions.