I would look no further than Rock River Arms or RRA. Their Varmint A4 models have 3/4 MOA accuracy guarantee and come loaded with "upgraded" components. They have a Wylde chamber that is safe or .223 or 5.56, 2 stage trigger that is very nice, Wilson "Match" barrel, Hogue grip and did I mention the accuracy guarantee?
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The RRA Varmint A4 has a 1:8 twist which will stabize heavy bullets. My RRA shoots 60gr V Max into the same hole. My buddy has a RRA Varmint A4 in 20" and it shoots the 50gr bullets quite well. I'd say the 1:8 is pretty versitile.
I'm by no means an AR expert but I have shot RRA, DPMS, and Bushmaster ARs.
I will tell you the DPMS (.204) had the worst trigger of any rifle I have ever shot. It may have been an isolated case and I'm not bashing DPMS but I actually quit trying to pull the trigger and looked at the safety to make sure that I had disengaged it. My buddy that owns the rifle started laughing; he was standing there waiting for me to check the safety because he knew the trigger is "stiff". The trigger felt like it broke at 20lbs. I will admit that 5 shot groups were about an inch and a trigger is easy enough to fix/replace.
The Bushmaster's trigger is sloppy, creepy and has a lot of slack before breaking. The accuracy was good but not great.