Yep, I spent a year or so putting together a dedicated long range AR in .260 Remington.
With two different 130gr factory loads it's consistently shooting right around .5moa off of a good rest.
It's not a cheap route to go to get that kind of accuracy though. You could get a lot of nice custom and semi custom bolt guns for the same money or less.
DPMS upper/lower. 24" Krieger ultra match stainless bbl.
JP trigger, complete drop in unit.
IOR Valdada 4-14x50 Tactical scope setting on top.
In the photo it still has the original DPMS factory free float tube but I have upgraded to the APEX Gator Grip handguard system. If I get time tomorrow I'll get a picture of it in the current configuration.
The pictured target is a full 20rd magazine fired in under 2 minutes at 250yds in a 25mph wind. Since I was shooting off of the tail gate getting completely steady was impossible and it still shot sub 1.5" at that range.
If you want to go the custom LR AR platform route give Karl a call at Rifle Accuracy Systems Inc in Colorado
. He's an absolute artist with either AR's or even Mini 14's. You will pay for his level of precision, but then you will pay for it with anyone else as well.