New to the forum and will be going through many posts to find any answers i am looking for hopefully. Looking to build an AR upper in 223 wylde for shooting up to 600 yards. Looking at aero precision  uppers and handgaurds either M4E1 or the enhanced. White oak armament for the barrel 1:7 or 1:7.5 twist rate.Adjustable gas block for future suppressor. Not sure on which BGC to get yet. Will most likely change my buffer tube assembly out also. I will be reloading 55/62 grain fun day rounds and 75gr to 80ish grain for longrange shooting. Any advice on BGC and buffer tube assembly to purchase. As any advice here is going to roll over to my 6 ARC build where i may invest a little more cash. Ty for your info and time. Also looking at complete uppers from precision firearms and white oak armament due to having correct head spacing.