First, i know NOTHING about this platform. I was at my Brother's house and one of his neighbors stopped by and we were bbq-ing, cocktailing and talking about guns. I mentioned I've been thinking about an AR for over a year or two now. I told my Brother's neighbor that I've settled on a Ruger Ar556 or S&W Sport 2. He said "they're ok, but I have something better you can buy off me". He opens his trunk and there's a Bravo Company 16" mid length upper MCMR-13 with the bolt and charging handle (both BCM). Unfired. Sorry i cant snap a decent pic tonight but it looks like this.. I have no clue what this brand is or even what id do with it. Neighbor guy says its one of the best and you can buy this off me for $700 or spend the same on finished trash. I quickly Googled the price of the BCM and figured it was a good deal. So now I'm a clueless AR upper owner. Can I go to my ffl and buy a complete lower and plug it in and play? Legos, guys keep saying. What do I need to finish this upper? Can I just plug in a complete lower like the one pictured above and be good to go? If I can, is PSA good for a complete lower? What do you guys recommend. I really need my hand held with this one. I'm lost on ARs.