One of the first platforms the railgun will be gracing is, not surprisingly, ships. Particularly, battleships and destroyers. Due to the large power requirements of the gun— a 25 megawatt power plant and large capacitor bank— only ships can carry it, with the most likely candidate being the DDG 1000 Zumwalt-class destroyers and its 78-megawatt integrated power system
The Navy retired much of its gun battleships after WWII, due to limited range and accuracy of gunpowder weapons. Missiles and jet fighters became the name of the game during the Cold War, extending range of ship operations. Now, battleships may get a resurgence.
The Navy’s current 6-inch guns have a range of 15 miles (24 km). The 16-inch guns of WWII battleships are at 24 miles (38 km). In contrast, the railgun has a range of 125 miles (201 km).
When fitted with railgun tech, the range of 6-inch Navy guns was extended to 38 miles (61 km). The Army’s 155mm howitzers also got extended range when fitted with the tech.
Although the railgun concept appears to be as old as studies of electromagnetism, science fiction fans (or should I say, fans of scientifiction) were treated to a futuristic treatment of these devices in The Battery of Hate, a 1933 story by John W. Campbell. He called them electric machine guns:
"What was that thing you cut those planes up with? I thought you were making a sort of machine gun."
Kennedy chuckled. "It was, Bob, it was. It was simply a long solenoid that threw little steel bullets, but it didn't use powder, it used electric power. Remember, there was practically no mechanical apparatus about it, only electrical contacts made by the bullet itself, as it was drawn throught the tube by the magnetic force. The lack of mechanism meant it could fire as fast as bullets could go through the barrel; no waiting while the thing was cocked and the used cartridge removed... The result was that the machine gun shot something like thirty thousand times a minute. It acted like a huge bandsaw, each bullet being a tooth that moved better than two miles per second."