Very informative link, thanks.
Although now I'm starting to think that maybe it would just have been easier if I ordered my upper receiver from Bushmaster along with my barrel so they could assembly it for me. I would have paid alot extra for my upper from Bushmaster, but I would have saved myself the hassle of assembling this myself. My barrel from Bushmaster didn't ship yet, and I probably could call them and see if I can add an upper to my order.......But then again, it'll be a good learning experience if I just go ahead and assemble this thing on my own.....