The 5"/54 Mk 45 gun, developed in the early 1970s, is the newest of the 5-inch guns in the fleet today. It is found aboard the DD-963, the DDG-51, the LHA-1, and the CG-47 class ships with the Mk 86 GFCS. The Mk 45 gun is currently found in two versions-the Mod 0 and the Mod 1-with Mods 2 and 3 currently under development. The Mod 0 is currently being replaced with the Mod 1. The major differences between the two is that the Mod 1 is designed to fire guided projectiles and has electronic upgrades in its control circuits. These will not be covered in this text since the main components of the loading system are very similar.

The Mk 45 (fig. 6-13) is a fully automatic, dual-purpose, lightweight gun mount capable of firing the full range of 5"/54 projectiles, including RAP (rocket-assisted projectiles), at a rate of 16 to 20 rounds per minute. During normal operation, the loading system (fig. 6-14) is operated locally by the mount

Figure 6-14.-The 5"/54 Mk 45 gun-loading system; major components. 6-13

captain while gun laying, fuze setting, and firing orders are generated by the FCS. The gun maybe positioned locally from the EP2 panel for maintenance purposes only.

Crew Positions and Responsibilities

The manned positions on the Mk 45 gun during normal operations are the EP2 panel operator, the mount captain in the loader room, and a magazine crew in the magazine. The gun mount itself (upper gun) is unmanned. The mount power distribution panel, EP1, is the mount captain's responsibility.

The loader drum holds a total of 20 complete rounds of ammunition. Before an operation, the magazine crew will load the drum, through the lower hoist, with 20 rounds of various types of ammunition. The loader drum can also be loaded in the loader drum room through the upper loading station.