I saw the news about the navy testing a rail gun that can hit targets 100 miles away (w/o all that big gun recoil) and was pretty impressed. Then I found this. Unfortunately, it seems that the actual instructions are have been deleted by the 'authors'. If you go down through the comments you will see that the kilojoules produced are on the lines of a .45 but still....
Oh, the navy shot is about 33 megajoules and travels 100 miles in 6 minutes. A Tomahawk missile costs US$600k each - you can build a couple rail guns for that.