The 6-inch shield gun was one of the last coast artillery weapons systems developed for the United States. These guns were designed to provide intermediate range defense, primarily against smaller ships, such as light cruisers and destroyers. Part of the 1940 coastal defense program, 50 two-gun batteries were to be built in the continental U.S. However, some batteries were never constructed, and others were never actually armed as resources were diverted to other projects as the World War 2 turned in favor of the Allies.
Each of the batteries consisted of 2 shield guns with a magazine usually located between and to the rear of the gun positions. The magazine contained generators to provide power and high pressure air (used to clear the chamber of fragments after firing), along with projectiles and powder.
The shields surround the gun, except for the open area at the rear. They are made of cast steel, and range from 4-6 inches in thickness. This was considered to be enough to protect against light weapons fire, and near misses from heavier shells. The weight of the gun carriage and the shield is 142,000 lbs.
Mounted on the M1 barbette carriage used with the shield gun, the weapon had a minimum elevation of -5 degrees, and a maximum elevation of 46 degrees. The guns mounted in many cases had been removed from disappearing carriage batteries which had been declared obselete. The additional elevation gained by mounting these guns on the M1 carriage greatly increased their range, from 16,000 yards (9 miles) for the Endicott period gun carriage, to 27,000 yards (15 miles) for the M1 carriage. The projectiles used ranged from 90-105 lbs, and the propellant charge ranged from 32-37 lbs.
Each gun was serviced by a gun section composed of a gun commander and 25 enlisted men. These were broken down into a gun squad of 12 men, which managed firing of the weapon. The other 12 men were detailed to the ammunition section, who supplied the ammunition from the magazine.
Very few of these weapons survived the scrapping of the coastal defense batteries that took place after the end of World War 2. One of the locations at which examples of these weapons can be found is the Gulf Islands National Seashore, Fort Pickens Unit. These weapons are not the orginals, but were moved to Fort Pickens from Fort John Custis in 1976. Below are a couple more pictures I have of these weapons.
Front view of the eastern shield gun, with the top of a spotting tower in the background.
A shield gun viewed from the rear. Note the thickness of the cast steel shield along the top.