Re: long range predator AR
RR Predator Pursuit is a good factory choice; call Scott at Specialized Dynamics for a custom build from a stand-up HIDE vendor
---could also try Robert at RWS or Chaos Arms or Liberty Arms
personal long-range AR15 favorites are 24" 204, 22" Grendel, 26" 223-----Shilen, Satern, and Krieger barrels
decide on your personal budget first!
almost forgot White Oak----excellent uppers or barrels