It can definitely be more accurate than contractor-grade barrels, and cheap mil-spec barrels. Trust me, I used to feel the same way, until I built mine, and used all high-end parts, and it really is like a whole different rifle than those ****** old off-the-shelf mil-spec M4's. The only advantage they have is that fun 3-position giggle-switch...But it's not practical in any sense, other than suppressive firepower.
Anyway, back to your conundrum...
I would go with a nice match-grade barrel like one of the 3 I linked, with a good gas block and a good stainless gas tube.
I would go with a good handguard, like the Seekins Precision MCSR V2 Keymod 15" rail...
http://www.seekinsprecision.com/mcsr-rail.html And it will come with it's own proprietary barrel nut.
As for triggers, I recommend the Rise Armament RA-140 trigger. For the price, it is nearly unbeatable...
https://www.rainierarms.com/rise-armament-black-fallout-trigger/
I spent more on each one of my uppers than most people spend on their whole AR build. It pays for itself when you go to the range and it shoots MOA or better (which is better than 90% of the other people's hunting rifles that are shooting around you
). You really realize the platform CAN be accurate, and LR capable...You just can't skimp on anything, and must buy match-grade and top-tier quality parts...Including the upper and lower receivers.