Immunity Zone Slide Rules
152mm L/47 105lb shell
152mm L/47 130lb shell

   For the new light cruisers of the Brooklyn class, the first laid down since the Omaha class of 1921, a new 6" gun was put under development, leading to this gun. The 152mm L/47 was mounted in the Brooklyn and Cleveland class light cruisers (of course also in the Fargo class, a one-smokestack variant of the Clevelands only serving post-war), in both cases in triple turrets. The 152mm L/47 was an exceptionally deadly gun in ship-to-ship combat. It first saw action in this role when the cruiser Nashville despatched a Japanese picket boat during the Doolittle Raid, but its true distinction came during the night battles in the Solomons. There, cruisers Honolulu, St. Louis, Helena, Boise, Cleveland, Montpelier, Denver and Columbia carried their 6"s in battle. The rapid-firing 152mm gun - it employed semi-fixed ammunition, but fired at an astounding rate of 12 rounds per barrel per minute, thanks to semi-automation of the loading process, for a total of 180 rounds per Brooklyn class ship per minute, or 144 per Cleveland - was the only medium gun capable of operating successfully against Japanese destroyers. The 203mm L/55 of the heavy cruisers could not track them adequately.

    Recently, some comment has been made on the problems with the gun; that its fire tended to obscure the target and radar was unable to distinguish between the shell splashes and subsequently targetted the splashes. These errors in its employment, however, do not lessen the contribution of this gun to the U.S. Navy's victories in the Solomons.

    This rate of fire proved the only effective gunfire means of dealing with IJN destroyers. Thus, after the disasterous battle of Tassafaronga, the heavy cruisers originally with the bombardment forces in the Slot were removed and replaced by increased numbers of light cruisers.

    In the battles of Vella Gulf, off Kolombangara and at Empress Augusta Bay, the 6" fired to good effect on enemy destroyers (including a spectacular first-round hit on the light cruiser Jintsu at Empress Augusta Bay by RADM A. Stanton Merrill's Cleveland-class cruisers).

    Post-war, the 6" L/47 was employed in the AA cruisers of the Worcester-class in twin turrets, as main AA weapon. It remained in service aboard Cleveland-class guided missile cruiser conversions into the late 1970's. 
Compared to the IJN's and the Royal Navy's 152mm guns, the U.S. gun was not too special, but had a higher rate of fire and slightly longer range compared to the RN, and a far higher rate of fire (over twice as quick) compared to the IJN

Another L/47-gun was used in the U.S. Navy gunboats Erie and Charleston. That gun used a 105lb shell.