For the AR, get the 60-65 grain Hornady Tap ammo with the ballistic tips. Good and dependable... Every shot at two hundred meters+ will group in a paper plate.
Just playing and gettin yer ya-yas out, plain old PMC works just fine...
Second the TAP, good stuff in the 60-65gr range. Also look into the Black Hills' Mk262 Mod1 (77gr), it's extremely good stuff. Very accurate.