If you are serious about wanting the "Best" and "most accurate" then I'd point you in Andrew Brady's direction. He owns and runs Lone Star Armory. Andrew "builds" custom ARs based on his machined receiver sets. He will spend time getting you know your wants and need in a rifle and build to suit. I have handled and shot many of his AR based rifles in .223/.556, 6.5 CM, 308 and 6.8. I'd rate the accuracy second to none. Andrew "hand builds" and test fires every rifle himself; he is the assembly line.

I know you want a light weight AR build and I'm sure he can accomidate that but these are a couple of groups from two different AR rifles he built. Neither of these are light weight but as you can see the accuracy speaks for itself.

Both rifles were built by Andrew Brady from Lone Star Armory.

Here are a couple of thousand yard groups that Tye shot from his 6.5 CM rifle.

Another 5 shot group


This is a 700 yard group that was fired from Wes's 6.5 CM at 700 yards. I witnessed Jeremy Moore from Shooter's Source shoot this group.

JP

With Lonestar armory rifles, you don't aim at the bulls eye. You aim at the thumb tac holding the paper


100 yard 5 shot load development

Christensen Arms CA15
http://www.christensenarms.com/products/msr/ca-15-recon/

Carbon wrapped barrel, very accurate, if money is no object