Lol no one. =P and prolly won't for a while. Check JsE surplus, palmetto armory, Primary Arms, YHM, Brownells, Buds... Etc. more than likely they're all bought and on back order indefinitely for a while. A long while.
Be best off just waiting around till this bill fails or passes. As long as ya have a lower and it's registered you won't have any problem assembling a rifle I wouldn't think. They're not banning individual parts yet, just the sale of new ones. (Should it pass).
That's what I was afraid of. This reminds Me of the great ammo rush when the King took the throne. By the way do You know of anyone putting a 6.8 upper on a mil spec lower?
I have been told the mil spec lower in 5.56 is interchangeable with no mods.
Should be interchangeable as long as you swap out mags and BCG. I've heard people swapping out the uppers with .50 Beowulf and not having any trouble. If its mil spec I see no issues to be concerned with.