I'm in the process of putting together an AR-15. I plan on building a target/varmint (coyote/sage rat) gun. Most shooting will be 300 yards and under, occasionally stretching the distance to 600 yards (my range's maximum). I'm pretty much set on a 20" bull barrel with a 1/8 twist, but deciding on a manufacturer has been difficult for me. My build is starting with a complete lower that I'm purchasing from a NWFA vendor, Stoner Arms. It consists of: Mega lower receiver with a RRA LPK, and an A2 stock. Upper receiver has not been purchased as of yet. I will be using a free float tube, no rails needed, as I am going to be putting a decent scope on this. Any opinions as to which upper receiver to buy? What about barrel manufacturers? I notice most "varmint" rigs I've seen sport Stainless barrels. I like the look of a black rifle with a stainless barrel, so that is OK with me. I DO know that I'm not interested in a 24" barrel at this time. This is my first build, and I would appreciate any information or advice you guys can offer. Thanks!