Bear Creek is responsible for me learning to assemble my own ARs from scratch, because over the years I have had to take apart and correctly reassemble their lowers and uppers numerous times. Their barrels are usually pretty good shooters, though occasionally I've had to send one back that was completely out of spec. Don't be surprised to find the barrel nut coming loose on your upper, or the 2 out of the 6 handguard screws being locktited while the other 4 are loose, or find the castle nut loose the first time you use the rifle.
But they do offer a lot of variety of calibers and barrel lengths, and the occasional match grade barrels they have offered have been excellent. I have found their customer service hit and miss over the years, but they have eventually rectified the issues I have encountered. I cannot recommend their lowers, however. I live near and work in Houston, TX, and Primary Arms has a great selection of stripped and full lowers as well as parts kits, etc, that allow me to easily customize my ARs.
Bear Creek can be a good deal, but they can also be so poorly put together at times you wonder how they passed inspection and were shipped out. I've talked to their warranty staff numerous times, and they claim they make every part for the rifles in house. In the end I have never had one of their uppers that did not end up shooting good, even if I had to send it back to get the barrel replaced. Remember to keep the shipping box. I hope this helps.