I've done an experiment a few times of trying to extract more accuracy from an AR by using all of the fancy reloading techniques I used in bolt guns.
I've gotten multiple batches of one fired LC brass. I sorted it by year, then sorted by weight. I then annealed, neck turned, flash hole deburred, and fired about 500 cases to 'form' them.
Once 'formed' I sized them with about .015 of tension, and a .003 bump. Charges were weighed down to the kernel.
Compared side by side with the 'discards' of the same batch that were just sized in a standard Redding FL sizer, and drop charged, they shot the exact same.
There are clearly exceptions, but generally speaking, an AR has a much harder time shooting the difference between basic prepped rounds, and rounds that have had a full prep/workup.
If you're single feeding way out past mag length, and running these through a Bartlein/Kriger, you'll probably be able to see some goodness (still way less than a bolt gun).
If it's just a stainless barrel from one of the AR-focused companies out there, I wouldn't waste time on getting real fancy with it. Get consistent neck tension and seating depth, and if shooting 1,000, a consistent powder charge.
If you were going to buy anything at all, buy some 123 Lapuas and some 8208 XBR.
A Grendel can get out to 1,000, but it's going to get real interesting in any amount of wind.