For a good battle ready AR15 look into.
BCM, LMT, Colt, Daniel Defense, Noveske and KAC.
These are no nonsense weapons. A properly built AR15 is a very reliable weapon with a need for lubrication every so often. A good 5.56 hollow point or soft point is a very devastating bullet.
For the .308s the M1A, FAL, and G3 models are also very good selections.