I was looking into an Ar-10, and I've gotten distracted by Ar-15 variants. The 6.8 has specifically caught my attention due to the fact I've heard the 6.5 Grendel is very touchy. I would like it to be accurate for 300 and beyond that is a good bonus. I want to have no problems taking down a deer at 300 yards, I'm thinking at least a 100 grain bullet. Do you have suggestions on either caliber and where should I look at getting barrels? Price is semi important here. All help is appreciated.