US Railgun is being test fired a few times per hour now and by the end of the year at 10 shots per minute

The US Navy railgun program is making great technical progress according to the Office of Naval Research program manager Tom Boucher.

The Navy is now working towards installing railguns at permanent land-based test sites which would provide more and better data for fewer dollars than an ad hoc installation aboard a repurposed fast transport.

New 32-megajoule railguns have been installed and fired in Virginia and New Mexico.

White Sands (New Mexico) tests the long-range performance of the projectile, Dahlgren (Virginia) will work on the weapon itself. Previous test weapons were only firing a few times per day. The Dahlgren team is now making multiple shots per hour as they work out the bugs, and by the end of the year they expect to reach the goal of 10 shots per minute.>b For comparison, a standard 5-inch deck gun can fire 20 rounds a minute, albeit only for a single minute before its quick-reload drum runs empty; the 16-inch guns on battleships fired about twice a minute.

Once they've reached the 10-round a minute rate then they will work to make the railgun barrel last for 1000 shots or more.

The current railguns fire a 16 kg slug at 2,000 meters per second (Mach 5.8), which takes 32 megajoules of energy per shot.
10 shots minute would need 20 megawatts of power.
Only 11 nuclear-powered aircraft carriers and three Zumwalt-class destroyers currently have the power for a railgun.

Navy strategist Bryan Clark has proposed adding cargo containers full of batteries to convert EFP transports into expedient railgun platforms to shoot down incoming missiles. The batteries in one container could power about ten shots.