The Gene Stoner rotating bolt is a brilliant engineering marvel that advanced self loading rifles by a century! You can't go wrong with a AR!
Baldy, check out your local military surplus store or online and pick up a army/airforce/marine FM on your rifle. This is a good one here for a intro on how it works!
Chapter 4 is the fundamentals but the rest is fun reading too!
BTW, can you PM me with how much you paid? I'm looking at getting another AR and converting my current lower with its trigger and stuff into a 6.8SPC.