Head - yours looks almost exactly like mine except I have a different forearm and a front sight. Mine has the removable carry handle. And I have a 20" barrel, but it isn't a bull barrel. I see you installed a scope using some high rings on top of mounting blocks. I went with the super high rings. I figure one less thing to come loose.
This is my first AR style. And until I got it, I was unaware of all you can do with them. The interchangeability seems never ending. Some of the uppers you can get are 204, 223, 6.5, 6.8, 308 the Rugers, and on and on. Different barrel configurations, stocks. Its like a multi round Contender or Encore.