Oh and in answer to your AR-15 question: you're barking up the wrong tree here. Go visit one of the most trafficked forums on the net:
AR15.Com . Avoid the General Discussion area, with millions of accounts and being up for so many years, it's pretty much turned into an opinion cesspool. But over in the technical sections you can find pretty much any firearms info you'll ever need.
Edit: here's a link to the correct subforum for FAQs and posts and whatnot about building your own AR:
http://www.ar15.com/forums/forum.html?b=3&f=4