The 8"/55 (20.8 cm) caliber gun Mark 15 formed the main batteries of United States Navy Baltimore-, Oregon City-, Boston-, and Albany-class cruisers. This gun is similar in construction to the previous 8"/55 caliber Mark 12, and related to the 8"/55 caliber Mark 9, 10, 11, 13, and 14 (but of much lighter construction) which served as the main guns for several earlier heavy cruisers as well as the self-defense guns on the only two Lexington-class aircraft carriers, the first operational aircraft carriers in the US Navy, until their removal at Pearl Harbor in 1942 to be used as coastal artillery. It was superseded by the improved 8"/55RF caliber gun Mark 16 by 1948, which were only installed on three Des Moines-class heavy cruisers.
Powers and Stats
Name: 8”/55 caliber Mark 15
Origin: Real World
Classification: Baltimore-, Oregon City-, Boston-, and Albany-class Heavy Cruiser Main Gun
Attack Potency: Small Building level (34–80 megajoules); 3–4 rounds per minute rate of fire
Speed: Supersonic (610–762 meters per second)
Durability: At least Small Building level, at most Large Building level with biggest turret mount in terms of total destruction (comprised of up to 336,450 kilograms of steel with a fragmentation energy of 8.9 gigajoules)
Stamina: Barrel life of 715 rounds
Range: Up to almost 27.5 kilometers, up to 66 kilometers with Long Range Bombardment Ammunition (post-late 1960s only)
Weaknesses: Manually loaded, requires about 66 men to operate one turret
Note: Similar naval guns of about the same bore (200-210mm) and period generally have performance equivalent to this one.