Battleship Craft Naval Archives Wiki

The Mk-1B Railgun on the deck of the USS Jackson Thomas (DDG-150)

The Mark-1 Surface-Mounted Railgun, also known as the Mark 84 5"/40 caliber turret, is a ship-mounted turret in service with numerous nations. First tested in 2009 and first used in 2013, this turret is the world's first fully operational railgun.


The Mk-1 railgun was originally meant to replace both the Mark 7 and Mark 45 5"/38 caliber turrets by Quarter 1 of FY2016, but the United States Navy decided to keep both of the turrets and decided to have the proposed railgun applied to Flight III Arleigh Burke-class guided missile destroyers. In 2008, Harmon Military Industries was selected as the company to design the gun and recieve the contract for production, only if it would fit on the 5" turret rotation system and fire from a ship.

Engineers wanted to give the railgun a rather simple design, but it was later made to resemble a railgun from a science-fiction movie. Testing of the gun was done in the Arizona desert in 2009, and tests would later be done over the next three years. The HMI team decided to test the gun on the USS Kidd (DDG-100) in 2012, but feared that the diesel-electric turbines of the ship would be unable to generate enough power for the gun to fire. The Navy then ordered the Kidd to enter drydock in Marinette, Wisconsin to be refitted with a slightly improved turbine generator system.

The 38 caliber prototype was transported to Wisconsin one week after the Kidd entered the Great Lakes for the first time, and was attached to the ship's deck on Christmas Eve. Trials were then set to begin on January 4 off the coast of Milwaukee.

USS Kidd (DDG-100) operating it's Mk-1 Surface-Mounted Railgun during the Battle of Chicago in 2014.

On January 4, the Kidd reached the testing range and conducted the railgun's first tests. If the gun malfunctioned or not enough power was generated, then the railgun would later be saved for the Zumwalt-class. But despite what they thought, the tests were a success. Evaluations of the test calculated that the tungsten projectile travelled at a speed of Mach 2 and had an impact force of 27 megajoule (MJ). The United States had created the world's first operational railgun.

After the Kidd completed the tests, the railgun was removed to be at the contract awarding for the turret, and was remounted to the ship two weeks later. Two months later, a newer design registered as the Mk-1B, what is commonly today, had a more "tactical" appearance and slightly larger caliber, firing projectiles at Mach 2.5 and 28MJ of force, which was proved effective during both World War III and the Western War onboard the USS Nighthawk (BBGS-75).

In 2014, it was discovered that the Mk-1 railgun can operate in zero gravity, and the USS James A. Lovell (DDA-01) became the first aerospace warship to have the gun as it's primary armament.

After Harmon Military Industries closed in 2015, the Atlas Corporation picked up the production rights to the Mk-1 railgun.


(This is for ships that use the Mk-1 Surface-Mounted Railgun)



  • United States of America
    • United States Navy
  • Alliance of Imperial Fleets
    • Imperial Kevin Navy
    • Enterprise-Conneticut Division
  • United Aerosppace Command
    • UAC Navy


  • Millennium
    • Millennium Navy
  • New Republic of the Pacific
    • NRP Imperial Navy


  • The Mk-1 railgun is represented by the Railgun in Hansa 2.4.