re: help on an AR-15 build

OP, since you seem so new to the platform and appear to just be seeking a basic AR15, I would highly recommend you just go out and grab a Smith and Wesson M&P Sport II or a Ruger AR556. There are a plethora of dealers overstocked with them and you should be able to find one or the other for $500 online. These are both great starter rifles that you can upgrade later as you get comfortable with the platform. They are also US made and from companies that have decent quality control and stand behind their products. Not all of the things in the last sentence are true about the uppers linked in this thread. Save yourself the headache and get something that is going to work out of the box this time around.