I'd have to say my Hesse/Blacktorne/Vulcan. After three 30 rd.mags only some minor
cracking in front of the castle nut after I butt slammed it to clear some FTE. The guy at the pawn shop said that was normal though and that all ARs will break there if you do that

Stag with a BCM Bolt/carrier.

That's rather specific.... I'm guessing it's what you have? :)

Any of the better makers would be ine IMO.  Frankly, just get Colt or BCM for a DI AR and save yourself the wondering.

Not really "off the shelf" but I have a Sabre upper with a Bravo Company bolt carrier group and it runs 100%.
My lower is a S&W with an RRA two stage trigger.

I'd get a complete Sabre or Bravo Company upper with a good lower you built yourself. I will go this way
again when I build another AR.

Of course Colt is good and we have had good luck with Rock River and Bushmaster AR's as well.

If money is no object I'm sure the good floks at LaRue can provide you with something very, very special.