Blackrifledepot.com, located in California, was the source for my first ar build. I bought a lower build kit from them that has surpassed the thousand round mark without a single issue. Still waiting on my pistol lower kit but I excpect the same. They shipped it out within 24 hours of ordering. Very reasonable prices as I paid 64.88 shipped for the pistol lower build kit with a brace included and about the same for my rifle lower build kit. They offer different options for the parts kits and also sell complete uppers. If you are looking at building an AR I highly recommend checking them out. 
