by samginko on Fri Jan 08, 2021 1:59 pm
I know it's too late, but for information purposes parts can still be found online. I just built an 11 1/2" 5.56 upper for about $400. I could have built a 10.5" 300blk upper for about the same price. This did not include bcg and charging handle, but they can be found online for about $150.
I found most of what I needed from at3 tactical.com, but I could have used multiple vendors.
On a side note, if your are intending to suppress the uppers, I would look at gas piston uppers that gives suppressor mode or no cycle mode. Not only quieter, you don't get the gas in your face.