Depends on what your after. I've found everything but a bcg (haven't had need to find a lower). So long as you don't care about the design of the rifle that is. Unfortunately I have two particular builds in mind. Been able to complete the lowers but haven't had much luck tracking down the parts for the upper
I called this 6 months ago. I knew it was coming, thank god I built a few before hand. Good luck guys! Don't forget to keep checking Brownells, as they are the largest supplier in the country. They may be out when you check, but the typically replace as quickly as they can.
Put your name on the mailing lists everywhere and be ready to buy when that part comes available. I purchased a BCM BCG 2 days ago that way. Got the email at 2:14, purchased at 2:18 and they were out of stock again by 2:25. That quick. I was just lucky to be checking my email when it hit.
I've lost track of all the backorders I have! Things are starting to trickle into retailers very slowly. Picked up a bolt and a bolt carrier today. Not a package, but separately. Not ideal, but hopefully they'll work together. PSA had BCM BCGs the other day and they were sold out in minutes. Insane.