Why Long Beach retained 5-inch/38 guns

Why did Long Beach use 5-inch/38 mounts instead of newer 5-inch/54 guns?

The mounts were available, light, and easy to fit. Their proven operation also gave the ship a dependable fallback, although later Vietnam experience with early automatic 5-inch/54 systems could not have informed the original choice.

Long Beach's 5-inch/38 battery looks like a practical fit rather than a choice imposed by Admiral Hyman Rickover. The mounts were available, had a modest effect on the ship's design, and avoided the below-deck ammunition handling needed for the 5-inch/54 Mark 41. A Vietnam veteran's account contrasts failures in early automatic 5-inch/54 installations during sustained fire with a crew member visually checking the 5-inch/38 barrel before loading another round. A later weight comparison gives less than 20 tons for a 5-inch/38 mount and about 60 tons for the 5-inch/54 Mark 42, making topweight another plausible factor. The lighter guns also preserved a useful fallback if other systems failed.