The Advanced Gun System (AGS) is a naval artillery system developed and produced by BAE Systems Armaments & Services for the Zumwalt-class destroyer of the United States Navy. Designated the 155 mm/62 (6.1") Mark 51 Advanced Gun System (AGS), it was designed to provide long range naval gunfire support against shore-based targets. A total of six of the systems were installed, two on each of the three Zumwalt-class ships. The Navy has no plans for additional Zumwalt-class ships, and no plans to deploy AGS on any other ship. AGS can only use ammunition designed specifically for the system. Only one ammunition type was designed, and the Navy halted its procurement in November 2016 due to cost ($800,000 to $1,000,000 per round), so the AGS has no ammunition and cannot be used. The Navy will remove the AGS from the ships in 2023. History The Zumwalt-class and AGS were designed and developed in the context of the United States battleship retirement debate. Battleship proponents argued that the battleships should not be decommissioned until an alternative method of providing naval gunfire support could be deployed, while others argued that such support was no longer needed in the era of missiles and aircraft. There has been research on extending the range of naval gunfire for many years. The 203 mm 8"/55 caliber Mark 71 gun was the US Navy's Major Caliber Lightweight Gun (MCLWG) program. The system was designed and tested in 1975 but the program was terminated in 1978. Gerald Bull and Naval Ordnance Station Indian Head tested an sub-caliber saboted long-range round in a stretched 16"/45 caliber Mark 6 gun in 1967. The Advanced Gun Weapon System Technology Program (AGWSTP) evaluated a similar projectile with longer range in the 1980s. After the last battleship, the USS Missouri (BB-63), was decommissioned on 31 March 1992, the AGWSTP became a 127 mm (5-inch) gun with an intended range of , which then led to the Vertical Gun for Advanced Ships (VGAS). The original DD-21 (1994 precursor to the Zumwalt-class design) was designed around this "vertical gun", but the project encountered serious technology and cost problems. Originally designed for mounting as a vertical gun adapted from the VGAS design, this AGS was then designed and produced for mounting within a more conventional turret arrangement. The AGS was designed to deliver precision munitions at a high rate of fire and at over-the-horizon ranges. As a