Railgun Information Online

So if you haven't heard yet, there has been a sweet leak about halo 4's railgun. In short its a sort of mini spartan laser with a shorter warm up time. In it's current iteration it boast deadly accuracy and can kill instantly, therefore it is considered a power weapon. But don't expect to be destroying warthogs and blowing up tanks, as the effects on vehicles are reduced, being more of a kinetic energy smack akin to the brute shot or concussion rifle, than the destructive shock of a Spartan Laser when hitting an enemy vehicle.

This is a link to the forum discussion on the flood section of the official halo site.

http://www.bungie.net/Forums/posts.aspx?postID=72404170&postRepeater1-p=1#72404250

also check out some cool new videos like this one:

This second video gives you a rough idea of what the railgun will operate like, using Halo 3's spartan laser, although it will 'feel' pretty different in the final game :)