You asked about an "accurate" gun. That means different things to many people.
I will skip a bunch of typing and just say this; I would use a White Oak Armament upper in whatever configuration best suited my needs and tastes. I would put it on a good quality lower that had a decent trigger. A good Colt, BCM, whatever. That matters a lot less, as long as it is quality, and assembled by someone who knows what they are doing.
https://www.whiteoakarmament.com/I have used White Oak barrels and uppers in more than 2 dozen builds for guys and all shot very well. Usually using MK262 (77 grain Sierra Matchking), but that was what was available for them at the time and location.
Bottom line is that it is extremely easy to simply put a WOA upper on a good lower and be done.
