I used PSA parts on my 300 BO pistol build and they worked fine for me. Once you get your parts, there are a lot of YouTube videos that will step you through the process. It's not difficult at all, but just be sure to get the springs installed in the right direction. PSA occasionally runs really good deals on uppers. You might have to pick an upper up one month, then wait a couple of weeks before the BCG is on sale, but if patient, you can build a nice rifle for a decent price.