"very accurate" is going to limit you to that platform for the same dollars spent.
Accuracy with the AR platform is pretty much a function of tolerances/fit of the parts, a high quality barrel and match trigger.
There are other semi-auto platforms like the SCAR, but I don't see any of them being potentially "more accurate" than the same dollars spent on a high-end AR-15.
Mosin-Nagant Custom Shop/Bent Bolts
Gun-Kote/ Cerakote Refinishing
Criterion Barrels/ Savage Re-Barreling