It is not being tested at anything more than 50 feet.
And I've also been to Dahlgren Weapons Lab were it is being tested. They do not have a range big enough to test a weapon like this at any worth while range.
The testing is also not intended to show range. They are still dealing with barrel wear issues. Distance testing is not set to start until at least 2013.
-- -- The guns will eventually fire sleek projectiles (that may be guided) using pure kinetic energy to destroy targets. For now, the service is firing 40-pound bricks designed to test out the guns??? barrel strength and their ability to stay cool while firing up to ten rounds per minute. These tests are set to run through 2017, - -
Read more:
http://defensetech.org/2012/02/28/video-baes-new-railgun-firing-for-first-time/#ixzz1odDg92PB 
